radar equipment

Abstract

To provide a radar system capable of accurately detecting targets.SOLUTION: A radar system 10 includes: a transmission circuit that outputs alternately a first transmission signal with a first center frequency and a second transmission signal with a second center frequency, which is the center frequency higher than the first center frequency every transmission cycle; and a transmitting antenna that transmits the first and second transmission signals. The second center frequency is a frequency higher than (1+1 / Nc) times the first center frequency (Nc is an integer indicating the number of times each of the first transmission signal and the second transmission signal is transmitted in each transmission cycle within a predetermined cycle).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a radar device. [Background technology]

[0002] In recent years, radar devices using short-wavelength radar transmission signals, including microwaves and millimeter waves, which can provide high resolution, have been studied. Furthermore, to improve outdoor safety, there is a demand for the development of radar devices (wide-angle radar devices) that can detect not only vehicles but also small objects such as pedestrians and fallen objects over a wide angle range.

[0003] A radar device with a wide detection range is configured to receive reflected waves using an array antenna composed of multiple antennas (antenna elements), and estimate the angle of arrival (DOA) of the reflected waves using a signal processing algorithm based on the reception phase difference relative to the element spacing (antenna spacing) (Direction of Arrival (DOA) estimation). For example, the DOA estimation method includes the Fourier method, or methods that can achieve high resolution, such as the Capon method, MUSIC (Multiple Signal Classification), and ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques).

[0004] Furthermore, a radar device has been proposed that includes, for example, a receiver and a transmitter that are equipped with multiple antennas (array antennas), and that performs beam scanning by signal processing using the transmit and receive array antennas (sometimes referred to as MIMO (Multiple Input Multiple Output) radar) (see, for example, Non-Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-304417 [Patent Document 2] Special Publication No. 2011-526371 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-119344 [Patent Document 4] International Publication No. 2019 / 054504 [Non-patent literature]

[0006] [Non-Patent Document 1] J. Li, and P. Stoica, "MIMO Radar with Colocated Antennas", Signal Processing Magazine, IEEE Vol. 24, Issue: 5, pp. 106-114, 2007 [Non-patent document 2] M. Kronauge, H. Rohling, "Fast two-dimensional CFAR procedure", IEEE Trans. Aerosp. Electron. Syst., 2013, 49, (3), pp. 1817-1823 [Non-patent document 3] Direction-of-arrival estimation using signal subspace modeling Cadzow, JA; Aerospace and Electronic Systems, IEEE Transactions on Volume: 28 , Issue: 1 Publication Year: 1992 , Page(s): 64 - 79 Summary of the Invention [Problem to be solved by the invention]

[0007] However, methods for detecting targets in radar devices (for example, MIMO radars) have not been fully studied.

[0008] Non-limiting examples of the present disclosure contribute to providing a radar device that can detect targets with high accuracy. [Means for solving the problem]

[0009] A radar device according to an embodiment of the present disclosure includes a transmission circuit that outputs, in each transmission period, a first transmission signal having a first center frequency and a second transmission signal having a second center frequency that is a center frequency higher than the first center frequency, and a transmission antenna that transmits the first transmission signal and the second transmission signal, wherein the second center frequency is (1+1 / N) of the first center frequency. c ) times higher frequency than (N c is an integer indicating the number of times that each of the first transmission signal and the second transmission signal is transmitted per transmission period within a predetermined period).

[0010] These comprehensive or specific embodiments may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium, or may be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium. [Effects of the Invention]

[0011] According to an embodiment of the present disclosure, a radar device can detect a target with high accuracy.

[0012] Further advantages and benefits of an embodiment of the present disclosure will become apparent from the specification and drawings. Such advantages and / or benefits may be provided by some of the embodiments and features described in the specification and drawings, respectively, but not necessarily all of them may be provided to obtain one or more identical features. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 shows an example of non-uniform Doppler multiplex transmission. [Figure 2] Block diagram showing an example of the configuration of a radar device [Figure 3]A diagram showing an example of a chirp signal [Figure 4] FIG. 1 is a diagram showing an example of a radar transmission signal. [Figure 5] A diagram showing an example of a Doppler peak [Figure 6] A diagram showing an example of a Doppler peak [Figure 7] A diagram showing an example of a Doppler peak [Figure 8] A diagram showing an example of a Doppler peak [Figure 9] FIG. 10 is a diagram showing an example of Doppler determination processing; [Figure 10] Another example of a chirp signal [Figure 11] FIG. 1 is a diagram showing an example of the configuration of a radar device. [Figure 12] FIG. 1 is a diagram showing an example of a radar transmission signal. [Figure 13] FIG. 1 shows an example of Doppler multiplexing. [Figure 14] FIG. 1 shows an example of Doppler multiplexing. [Figure 15] A diagram showing an example of a chirp signal [Figure 16] FIG. 1 shows an example of Doppler multiplexing. [Figure 17] A diagram showing an example of the configuration of a radar receiver. [Figure 18] FIG. 1 is a diagram showing an example of the configuration of a radar device. [Figure 19] FIG. 1 is a diagram showing an example of the configuration of a radar device. [Figure 20] FIG. 1 is a diagram showing an example of the configuration of a radar device. [Figure 21] A block diagram showing another example of the configuration of a radar device. [Figure 22] FIG. 10 is a diagram showing another example of a radar transmission signal. DETAILED DESCRIPTION OF THE INVENTION

[0014] A MIMO radar transmits signals (radar transmission waves) multiplexed using, for example, time division, frequency division, or code division from multiple transmitting antennas (also called transmitting array antennas), receives signals (radar reflected waves) reflected by surrounding objects using multiple receiving antennas (also called receiving array antennas), and separates and receives the multiplexed transmission signals from each received signal. Through this processing, the MIMO radar can extract a propagation path response expressed as the product of the number of transmitting antennas and the number of receiving antennas, and performs array signal processing on these received signals as a virtual receiving array.

[0015] In addition, in MIMO radar, by appropriately arranging the element spacing in the transmitting and receiving array antennas, the antenna aperture can be virtually enlarged, thereby improving the angular resolution.

[0016] [Time division multiplexing transmission] For example, Patent Document 1 discloses a MIMO radar (hereinafter referred to as "time division multiplexing MIMO radar") that uses time division multiplexing transmission, which transmits signals by shifting the transmission time for each transmitting antenna, as a multiplexing transmission method for MIMO radar. Time division multiplexing transmission can be implemented with a simpler configuration than frequency multiplexing transmission or code multiplexing transmission. Furthermore, time division multiplexing transmission can maintain good orthogonality between transmitted signals by sufficiently widening the transmission time interval. Time division multiplexing MIMO radar outputs transmitted pulses, which are an example of transmitted signals, while sequentially switching the transmitting antennas at a predetermined cycle. Time division multiplexing MIMO radar receives signals that are transmitted pulses reflected by an object using multiple receiving antennas, and after performing correlation processing between the received signals and the transmitted pulses, performs, for example, spatial FFT (Fast Fourier Transform) processing (processing to estimate the arrival direction of the reflected wave).

[0017] A time-division multiplexed MIMO radar sequentially switches the transmitting antennas that transmit a transmission signal (e.g., a transmission pulse or a radar transmission wave) at a predetermined cycle. Therefore, compared to frequency-division or code-division transmission, time-division multiplexed transmission can require a longer time to complete transmission of the transmission signal from all transmitting antennas. For this reason, for example, when transmitting a transmission signal from each transmitting antenna and detecting the Doppler frequency (e.g., the relative velocity of a target) from the received phase change, as in Patent Document 2, the time interval (e.g., the sampling interval) for observing the received phase change becomes longer when applying Fourier frequency analysis to detect the Doppler frequency. Therefore, the maximum Doppler frequency range based on the sampling theorem (e.g., the Doppler frequency range that can be detected without aliasing, or the range of the relative velocity of a target that can be detected) is reduced.

[0018] Furthermore, when a reflected wave signal from a target having a Doppler frequency exceeding the maximum Doppler frequency based on the sampling theorem is expected to be received, the radar device may observe a Doppler frequency of an aliased component that differs from the true frequency. In this case, it is difficult for the radar device to determine whether the reflected wave signal is an aliased component, resulting in ambiguity in the Doppler frequency (e.g., the relative velocity of the target).

[0019] For example, if a radar device transmits Nt transmitting antennas at a predetermined period T r When transmitting a transmission signal (transmission pulse) by sequentially switching between the r × Nt. c When repeating the above steps and applying Fourier frequency analysis to detect the Doppler frequency (detection of relative velocity), the Doppler frequency range in which the Doppler frequency can be detected without aliasing is ±1 / (2T r× Nt). Therefore, the Doppler frequency range in which Doppler frequency can be detected without aliasing decreases as the number of transmitting antennas Nt increases, and ambiguity in Doppler frequency is more likely to occur even at slower relative velocities.

[0020] [Doppler multiplexing] Since time division multiplexing MIMO radar may have the above-mentioned Doppler frequency ambiguity, the following will focus on a method of simultaneously multiplexing and transmitting transmission signals from multiple transmission antennas as an example.

[0021] As a method for simultaneously multiplexing and transmitting transmission signals from multiple transmitting antennas, there is, for example, a method of transmitting signals so that the multiple transmission signals can be separated on the Doppler frequency axis at the receiving unit (hereinafter referred to as Doppler multiplexing transmission) (for example, see Non-Patent Document 3).

[0022] In Doppler multiplex transmission, for example, a transmitter applies a Doppler shift amount greater than the Doppler frequency bandwidth of a received signal to a transmission signal transmitted from a transmission antenna different from the reference transmission antenna, and the transmission signals are transmitted from the multiple transmission antennas in the same transmission period (same transmission slot). In Doppler multiplex transmission, a receiver filters the transmission signals on the Doppler frequency axis, thereby separating and receiving the transmission signals transmitted from each transmission antenna.

[0023] In Doppler multiplexing, by transmitting transmission signals from multiple transmitting antennas at the same transmission period, the time interval for observing the received phase change when applying Fourier frequency analysis to detect the Doppler frequency (or relative velocity) can be shortened compared to time division multiplexing. However, in Doppler multiplexing, the transmission signals from each transmitting antenna are separated by filtering on the Doppler frequency axis, which limits the effective Doppler frequency bandwidth per transmission signal.

[0024] For example, in Doppler multiplexing, a radar device transmits signals from Nt transmitting antennas with a period of Tr This case will be described below. c Repeating this process, and applying Fourier frequency analysis to detect the Doppler frequency (or relative velocity), the Doppler frequency range in which the Doppler frequency can be detected without aliasing is ±1 / (2×T r For example, the Doppler frequency range in which the Doppler frequency can be detected without aliasing in the case of time division multiplexing (for example, ±1 / (2T r ×Nt)) is expanded by Nt times. r × Nc) + non-transmission period.

[0025] However, in Doppler multiplexing, as mentioned above, the transmitted signals are separated by filtering on the Doppler frequency axis. Therefore, the effective Doppler frequency bandwidth per transmitted signal is narrower than the Doppler frequency range in which the Doppler frequency can be detected without aliasing. For example, the Doppler frequency range in which the Doppler frequency can be detected without aliasing is ±1 / (2×T r ) is equally divided into Nt transmitted signals, the effective Doppler frequency range of each signal is 1 / (T r × Nt), the Doppler frequency range is the same as that in the case of time division multiplexing transmission. Furthermore, in Doppler multiplexing transmission, in a Doppler frequency band that exceeds the effective Doppler frequency range per transmission signal, signals in the Doppler frequency bands of other transmission signals different from the transmission signal in question are mixed together, which may make it difficult to correctly separate the transmission signals.

[0026] [Unequal Interval Doppler Multiplexing] As a method for expanding the maximum detectable Doppler frequency range in such Doppler multiplex transmission, for example, the Doppler frequency range ±1 / (2T r) into Nt+1 equal parts, and of the Nt+1 divided Doppler shift amounts, Nt Doppler shift amounts are assigned to Nt transmission signals, and the transmission signals are transmitted simultaneously from Nt transmission antennas (see, for example, Patent Document 4).

[0027] In this Doppler multiplexing, for example, since transmission signals are not assigned to some of the Nt+1 equally divided Doppler shift amounts, the Doppler shift intervals assigned to the Doppler multiplexed transmission signals (hereinafter referred to as "Doppler multiplexing intervals") are unequal. Hereinafter, this type of Doppler multiplexing will be referred to as "unequal interval Doppler multiplexing."

[0028] Next, an example of the reception process of radar reflected waves when non-uniform Doppler multiplex transmission is used will be described.

[0029] In the output obtained by applying Fourier frequency analysis for Doppler frequency detection (relative velocity detection), for example, among the Doppler shift amounts equally divided into Nt+1, the received power level of the Doppler corresponding to the Doppler shift amount to which no transmission signal is assigned is lower than the received power level of the Doppler corresponding to the Doppler shift amount to which a transmission signal is assigned. The radar device may estimate the Doppler frequency by utilizing, for example, this difference in received power level. By this estimation process, the radar device can estimate the Doppler frequency within the Doppler frequency range ±1 / (2T r ) makes it possible to estimate the Doppler frequency of the radar reflection wave.

[0030] In this way, by the unequal interval Doppler multiplex transmission that gives the Doppler shift at unequal intervals in the Doppler frequency domain, the divided Doppler frequency domain ±1 / (2T r × (Nt+1)), the radar system can detect unevenly spaced Doppler regions to suppress ambiguity in the Doppler frequency and reduce the maximum detectable Doppler frequency to 1 / 2T. r As a result, in unevenly spaced Doppler multiplex transmission, the detectable Doppler frequency range is expanded by Nt times compared to the method described in Patent Document 3, for example.

[0031] For example, in Patent Document 4, due to the constraints of the sampling theorem of Fourier frequency analysis, the maximum detectable Doppler frequency is 1 / 2T r Doppler frequencies (or relative velocities) exceeding the transmission period T r Although it is possible to expand the Doppler detection range by shortening the transmission period T r To shorten the transmission period T, an A / D converter with a faster sampling rate is used, which complicates the hardware configuration. In addition, increasing the sampling rate of the A / D converter may increase the power consumption or heat generation of the radar device. On the other hand, under the constraints of the sampling rate of the A / D converter, r If the distance is shortened, the detectable distance range may be reduced or the distance resolution may be degraded, which may result in a deterioration in the distance detection range or distance separation performance of the radar device.

[0032] In addition, in the case of non-uniform Doppler multiplex transmission, for example, when there are multiple reflected waves from the same distance to the radar device, and the Doppler intervals of these reflected waves are the Doppler multiplex interval (for example, "Δf DDM ") or coincides with a multiple of the Doppler multiplexing interval, the radar device is more likely to erroneously detect the Doppler regions with uneven intervals, which increases the likelihood of errors in separating multiple waves or errors in measuring the angles of multiple reflected waves.

[0033] For example, as shown in FIG. 1, a radar device uses Nt=2 transmitting antennas and performs unequal interval Doppler multiplexing using two of the three (=Nt+1) equally divided Doppler shift amounts. The radar device receives reflected waves #1 and #2 from targets at the same distance, and the difference in Doppler frequency between reflected waves #1 and #2 is Δf. DDM The case where:

[0034] (a), (b), and (c) of FIG. 1 show the output (for example, the output of the frequency analysis unit) when Fourier frequency analysis is applied for Doppler frequency detection (or relative velocity detection), where (a) of FIG. 1 shows the received power of reflected wave #1, (b) of FIG. 1 shows the received power of reflected wave #2, and (c) of FIG. 1 shows the combined result of the received signals of reflected wave #1 and reflected wave #2. The difference in Doppler frequency between reflected wave #1 and reflected wave #2 is Δf DDM Therefore, the reflected wave #2 in Figure 1(b) moves in the direction of +Δf on the Doppler frequency axis when the reflected wave #1 in Figure 1(a) moves in the direction of +Δf DDM It is in a shifted position.

[0035] As shown in (a) and (b) of Figure 1, of the Doppler shift amounts divided equally into Nt+1, the received power level of the Doppler frequency corresponding to the Doppler shift amount to which the transmitted signal is not assigned is lower (approximately at the noise level) than the received power level of the Doppler corresponding to the Doppler shift amount to which the transmitted signal is assigned, whereas in (c) of Figure 1, the received power level tends to be higher because it includes the received power of the other reflected wave.

[0036] For example, in the case of (c) of FIG. 1, the Doppler frequency -1 / 2T, which corresponds to the Doppler shift amount to which the transmission signal is not assigned, is reflected wave #1. r +2Δf DDM In the case of the other reflected wave #2, the transmitted signal coincides with the Doppler frequency corresponding to the assigned Doppler shift amount, so the received power level is likely to be high. Similarly, in the case of the reflected wave #2, the Doppler frequency -1 / 2T corresponds to the Doppler shift amount to which the transmitted signal is not assigned. r In this case, the transmission signal in the other reflected wave #1 matches the Doppler frequency corresponding to the assigned Doppler shift amount, so the received power level tends to be high.

[0037] In addition, since the received signal is composed of phase and amplitude, the received power obtained by combining multiple transmitted signals changes the value of the combined amplitude depending on the value of the phase. For example, in the case of (c) in Figure 1, r +Δf DDMThe Doppler frequency components of reflected wave #1 and reflected wave #2 match the Doppler shift amount assigned to the transmission signal, so they become the combined received power, and the combined amplitude value changes depending on the phase value.

[0038] In a radar device using non-uniform Doppler multiplex transmission, a radar receiver separates non-uniform Doppler multiplex signals by, for example, using a Doppler multiplex separation unit (described later) to detect Doppler peak positions that coincide with the Doppler multiplex intervals to which the transmission signals are assigned, and separates the Doppler multiplex transmission signals. At this time, the Doppler multiplex separation unit utilizes the fact that the received power of the Doppler frequency components of the Doppler multiplex intervals to which the Doppler multiplex transmission signals are not assigned to be sufficiently low, Separating the Doppler multiplexed signals.

[0039] By utilizing this difference in received power level, the Doppler frequency is within the Doppler frequency range of ±1 / (2T r ), and the Doppler multiplexed transmission signal can be separated. For example, in FIG. 1(a), the received power of reflected wave #1 is estimated uniquely within the Doppler multiplexing interval Δf DDM Matches -1 / 2T r and -1 / 2T r +Δf DDM The Doppler peak positions of the Doppler frequency components are detected, and the Doppler multiple interval Δf DDM Shifted Doppler frequency component (-1 / 2T r +2Δf DDM ) is sufficiently low, allowing estimation of the Doppler frequency and separation of the Doppler multiplexed signal.

[0040] However, for example, the Doppler frequency −1 / 2T in FIG. 1(c) r +2Δf DDM The received power at Doppler frequency -1 / 2T in Figure 1(a) r +2Δf DDMThe Doppler position is higher than the received power at (c) in FIG. 1, making it easier to make an error in estimating the Doppler frequency of the reflected wave #1, and the separation performance of the transmitting antenna deteriorates. r The received power at Doppler frequency -1 / 2T in Figure 1(b) r This results in a Doppler position higher than the received power at the reflected wave #2, making it easier to make an error in estimating the Doppler frequency of the reflected wave #2, and degrading the separation performance of the transmitting antenna.

[0041] In addition, in Figure 1(c), the Doppler frequency (-1 / 2T r +1Δf DDM ), the Doppler of Tx#2 of reflected wave #1 and the Doppler of Tx#1 of reflected wave #2, which have different phases and amplitudes, are combined, causing the phases and amplitudes to change from the states shown in (a) and (b) of Figure 1, resulting in a deterioration in angle measurement accuracy.

[0042] For example, in FIG. 1(c), the difference in Doppler frequency between reflected wave #1 and reflected wave #2 is +Δf DDM Therefore, the Doppler frequency (solid line x mark, -1 / 2T) corresponding to the Doppler shift amount to which the transmission signal is not assigned in the reflected wave #1 is r +2Δf DDM ) receives the Doppel frequency component of the reflected wave #2 to which the transmission signal by Tx#2 is assigned in an overlapping manner.

[0043] The difference in Doppler frequency between reflected wave #2 and reflected wave #1 is -Δf DDM Therefore, the Doppler frequency (dotted circle, -1 / 2T) corresponding to the Doppler shift amount to which the transmitted signal is not assigned in the reflected wave #2 is r ) receives the Doppler frequency component of the reflected wave #1 to which the transmission signal by Tx#1 is assigned in an overlapping manner.

[0044] Therefore, when reflected waves #1 and #2 are received from targets at the same distance, the difference in Doppler frequency between reflected waves #1 and #2 is Δf DDMIn this case, the Doppler frequency corresponding to the Doppler shift amount to which the transmission signal is not assigned (solid line x or dotted line circle in Figure 1(c)) will be lower than the Doppler reception power level corresponding to the Doppler shift amount to which the transmission signal is assigned (Tx#1 and Tx#2 of reflected wave #1 in Figure 1(a) and Tx#1 and Tx#2 of reflected wave #2 in Figure 1(b)).

[0045] However, the Doppler frequency corresponding to the Doppler shift amount to which the transmission signal is not assigned tends to be high because it includes the received power of the other reflected wave. For example, for the solid line x mark in (a) of Figure 1, it includes Tx#2 of the reflected wave #2 in (b) of Figure 1, so the Doppler frequency in (c) of Figure 1 is -1 / 2T r +2Δf DDM The combined received power tends to be high.

[0046] For this reason, the radar device is more likely to make an error in estimating the Doppler frequency in the state shown in Figure 1(c). If the radar device makes an error in estimating the Doppler frequency, it is more likely to make an error in properly separating the transmitting antennas, and angle measurement errors are also more likely to increase.

[0047] Furthermore, even if the Doppler frequency is estimated correctly, as shown in FIG. 1(c), if the Doppler multiplexed signal of reflected wave #1 and the Doppler multiplexed signal of reflected wave #2 contain the same Doppler component (Doppler frequency is -1 / 2T r +1Δf DDM ), and these are added (combined) as a complex signal, so the amplitude component or phase component changes from the state shown in (a) and (b) of FIG. 1, which makes it easy for the angle measurement accuracy of the radar device to deteriorate.

[0048] Therefore, in a non-limiting embodiment of the present disclosure, a method for expanding the range of Doppler frequencies in which aliasing does not occur (e.g., ambiguity does not occur) in Doppler multiplex transmission will be described. As a result, a radar device according to an embodiment of the present disclosure can accurately detect targets in a wider Doppler frequency range.

[0049] Furthermore, in a non-limiting example of the present disclosure, a method is described that enables the separate detection of each reflected wave even when the Doppler interval of each reflected wave from multiple targets at similar distances from the radar device matches the Doppler multiplex interval (or a multiple of the Doppler multiplex interval).

[0050] Furthermore, in a non-limiting example of the present disclosure, a method is described that expands the range of Doppler frequencies (relative velocities) in which aliasing does not occur in Doppler multiplex transmission, and that enables separate detection of each reflected wave even when the Doppler intervals of reflected waves from multiple targets at similar distances from the radar device match the Doppler multiplex interval (or a multiple of the Doppler multiplex interval).

[0051] A radar device according to an embodiment of the present disclosure may be mounted on a moving body such as a vehicle. Positioning output (information on estimation results) of the radar device mounted on the moving body may be output to a control ECU (Electronic Control Unit) (not shown) of an Advanced Driver Assistance System (ADAS) that improves collision safety or an autonomous driving system, and may be used for vehicle drive control or alarm generation control.

[0052] Furthermore, a radar device according to an embodiment of the present disclosure may be attached to a relatively high structure (not shown), such as a roadside utility pole or a traffic light. Such a radar device can be used, for example, as a sensor in an assistance system for improving the safety of passing vehicles or pedestrians, or in a system for preventing intrusion of suspicious individuals. Furthermore, the positioning output of the radar device may be output to a control device (not shown) in the assistance system for improving safety or the system for preventing intrusion of suspicious individuals, and may be used for alarm generation control or abnormality detection control.

[0053] The radar device is not limited to these uses, and may be used for other purposes.

[0054] Hereinafter, an embodiment according to an example of the present disclosure will be described in detail with reference to the drawings. In the embodiment, the same components are denoted by the same reference numerals, and redundant descriptions thereof will be omitted.

[0055] The following describes a configuration (e.g., MIMO radar configuration) in which a radar device transmits different multiplexed transmission signals simultaneously from multiple transmission antennas in a transmission branch, and a reception branch separates the transmission signals and performs reception processing.

[0056] In the following, as an example, a configuration of a radar system using a frequency-modulated pulse wave such as a chirp pulse (also called fast chirp modulation) will be described. However, the modulation system is not limited to frequency modulation. For example, an embodiment of the present disclosure can also be applied to a radar system using a pulse compression radar that transmits a pulse train after phase modulation or amplitude modulation.

[0057] (Embodiment 1) [Radar device configuration] The radar device 10 in FIG. 2 includes a radar transmitter (transmitting branch) 100 and a radar receiver (receiving branch) 200.

[0058] The radar transmitter 100 generates a radar signal (radar transmission signal) and transmits the radar transmission signal at a predetermined transmission period using a transmission array antenna configured by a plurality of transmission antennas 106-1 to 106-Nt.

[0059] The radar receiver 200 receives reflected wave signals, which are radar transmission signals reflected by targets (not shown), using a receiving array antenna including multiple receiving antennas 202-1 to 202-Na. The radar receiver 200 performs signal processing on the reflected wave signals received by each receiving antenna 202, and performs, for example, detection of the presence or absence of a target or estimation of the direction of arrival of the reflected wave signals.

[0060] The target is an object to be detected by the radar device 10, and includes, for example, a vehicle (including two-wheeled and four-wheeled vehicles), a person, a block, or a curb.

[0061] [Configuration of radar transmitter 100] The radar transmitter 100 includes a radar transmission signal generator 101, a signal generation controller 104, Doppler shifters 105-1 to 105-Nt, and transmitting antennas 106-1 to 106-Nt. For example, the radar transmitter 100 includes Nt transmitting antennas 106, each connected to a separate Doppler shifter 105.

[0062] The radar transmission signal generating unit 101 generates a radar transmission signal, for example, under control of a signal generation control unit 104. The radar transmission signal generating unit 101 includes, for example, a modulation signal generating unit 102 and a VCO (Voltage Controlled Oscillator) 103. Each component of the radar transmission signal generating unit 101 will be described below.

[0063] The modulation signal generator 102 periodically generates a modulation signal having a sawtooth shape, for example. Here, the radar transmission period is T r Let's say.

[0064] The VCO 103 generates a frequency modulation signal (hereinafter referred to as a frequency chirp signal or chirp signal, for example) based on the modulation signal output from the modulation signal generating unit 102, and outputs it to the Doppler shift units 105-1 to 105-Nt and the radar receiving unit 200 (mixer unit 204, described later).

[0065] The signal generation control unit 104 controls the radar transmission signal generation unit 101 (e.g., the modulation signal generation unit 102 and the VCO 103) to generate a radar transmission signal. For example, the signal generation control unit 104 may set parameters (e.g., modulation parameters) related to the chirp signal so that chirp signals with different center frequencies are transmitted alternately.

[0066] Hereinafter, the two chirp signals with different center frequencies will be referred to as the "first chirp signal" and the "second chirp signal," respectively.

[0067] FIG. 3 shows examples of chirp signals (eg, a first chirp signal and a second chirp signal).

[0068] As shown in FIG. 3, modulation parameters for a chirp signal include, for example, a center frequency f c (q), frequency sweep bandwidth B w (q), sweep start frequency f cstart (q), sweep end frequency f cend (q), frequency sweep time T sw (q) and frequency sweep rate of change D m (q) may be included. m (q)=B w (q) / T sw (q). Also, B w (q)= f cend (q)-f cstart (q) and f c (q)=(f cstart (q)+f cend (q) / 2. For example, q=1, 2 may represent the modulation parameters of the first chirp signal when q=1, and may represent the modulation parameters of the second chirp signal when q=2.

[0069] Also, the frequency sweep time T sw (q) corresponds to, for example, a time range (also called a range gate) for capturing A / D sample data in the A / D converter 207 of the radar receiver 200 (described later). sw For example, (q) may be set to the entire interval of the chirp signal as shown in (a) of FIG. 3, or may be set to a partial interval of the chirp signal as shown in (b) of FIG. 3.

[0070] 3 shows an example of an up-chirp waveform in which the modulation frequency gradually increases over time, but the present invention is not limited to this, and a down-chirp waveform in which the modulation frequency gradually decreases over time may also be used. Similar effects can be obtained regardless of whether the modulation frequency is an up-chirp or a down-chirp.

[0071] The signal generation control unit 104 selects, for example, a center frequency f that satisfies a predetermined condition. c (q) may be set (or selected) (examples are given below).

[0072] In the following, as an example, among the modulation parameters set for the first chirp signal and the second chirp signal, the center frequency f c The following describes a case where (q) is different from each other and other modulation parameters other than the center frequency are the same (or common). However, this is not limited to this. For application of an embodiment of the present disclosure, for example, it is sufficient that the resolution of the distance axis in the first chirp signal and the second chirp signal is the same. Therefore, the frequency sweep bandwidth B w It is sufficient to set chirp signals such that (q) has the same relationship (an example will be described later).

[0073] In the following description, the signal generation control unit 104 may, for example, determine the center frequency f c The modulation signal generating section 102 and the VCO 103 may be controlled so that two different chirp signals (q) are alternately transmitted Nc times each.

[0074] FIG. 4 shows an example of a chirp signal output by the radar transmission signal generation unit 101 under the control of the signal generation control unit 104.

[0075] In FIG. 4, the transmission period T r1 and the transmission period T of the second chirp signal r2 may be different (T r1 ≠T r2 ), or the same (T r1 =T r2 ) In the following, each transmission period T r1and T r2 The combined period is called "T rs For example, the transmission period T rs denotes the transmission period in which the set of first and second chirp signals is transmitted, and T rs =T r1 +T r2 In the following description, unless otherwise specified, each transmission period T r1 and T r2 represents a parameter with the same value (e.g., T r1 =T r2 ), for convenience, the transmission period T r It is sometimes written as:

[0076] Similarly, unless otherwise specified, the frequency sweep bandwidth, frequency sweep time (also called range gate), and frequency sweep rate represent parameters with the same values ​​for the first chirp signal and the second chirp signal, respectively. w (1)=B w (2)=B w , T sw (1)=T sw (2)=T sw , D m (1)=D m (2)=D m It can be expressed as:

[0077] Furthermore, the frequency sweep bandwidths of the chirp signals with different center frequencies may not include overlapping bands, as shown in Figure 4(a), or may include overlapping bands, as shown in Figure 4(b). In one embodiment of the present disclosure, similar effects can be achieved regardless of whether the frequency sweep bandwidths include overlapping bands, as long as the relationship between the center frequencies of the first chirp signal and the second chirp signal satisfies a predetermined condition.

[0078] In one embodiment of the present disclosure, the transmission period T rsmay be set to, for example, several hundred μs or less, and the transmission time interval of the radar transmission signal may be set to a relatively short time. As a result, even if the center frequencies of the first chirp signal and the second chirp signal are different, the frequency of the beat signal of the received reflected wave (e.g., beat frequency index) does not change, and the radar device 10 can detect this as a change in Doppler frequency.

[0079] Each chirp signal output from the radar transmission signal generation unit 101 (for example, the VCO 103) is input to, for example, each mixer unit 204 of the radar reception unit 200 and the Nt Doppler shift units 105, respectively.

[0080] The Doppler shift unit 105 adjusts the transmission period (for example, T r1 or T r2 ) Doppler shift amount DOP n To give the phase rotation φ n and outputs the Doppler-shifted signal to the transmitting antenna 106. Here, n=1,...,Nt. Note that the Doppler shift amount DOP n (For example, phase rotation φ n An example of a method for adding the .) will be described later.

[0081] The output signals of the Doppler shifters 105-1 to 105-Nt are amplified to a predetermined transmission power and radiated into space from the respective transmitting antennas 106 (for example, Tx#1 to Tx#Nt).

[0082] [Configuration of radar receiver 200] 2, the radar receiver 200 includes Na receiving antennas 202 (for example, Rx#1 to Rx#Na) forming an array antenna. The radar receiver 200 also includes Na antenna system processors 201-1 to 201-Na, a CFAR (Constant False Alarm Rate) unit 211, a Doppler demultiplexing unit 212, a Doppler determination unit 213, and a direction estimation unit 214.

[0083] The CFAR unit 211 may include, for example, a CFAR unit 211-1 and a CFAR unit 211-2 corresponding to the first chirp signal and the second chirp signal, respectively, which have different center frequencies. Similarly, the Doppler demultiplexing unit 212 may include, for example, a Doppler demultiplexing unit 212-1 and a Doppler demultiplexing unit 212-2 corresponding to the first chirp signal and the second chirp signal, respectively, which have different center frequencies. Although FIG. 2 shows a configuration in which CFAR units 211 are provided in parallel (CFAR units 211-1 and 211-2), a configuration in which a single CFAR unit 211 is provided and its inputs are sequentially switched for processing may also be used. Furthermore, while FIG. 2 shows a configuration in which Doppler demultiplexing units 212 are provided in parallel (Doppler demultiplexing units 212-1 and 212-2), a configuration in which a single Doppler demultiplexing unit 212 is provided and its inputs are sequentially switched for processing may also be used.

[0084] Each receiving antenna 202 receives a reflected wave signal, which is a radar transmission signal reflected by a target, and outputs the received reflected wave signal to the corresponding antenna system processing unit 201 as a received signal.

[0085] Each antenna system processing unit 201 includes a receiving radio unit 203 and a signal processing unit 206 .

[0086] The radio reception unit 203 includes a mixer unit 204 and an LPF (low pass filter) 205. In the radio reception unit 203, the mixer unit 204 mixes the received reflected wave signal (received signal) with a chirp signal, which is a transmitted signal. In addition, by passing the output of the mixer unit 204 through the LPF 205, a beat signal having a frequency corresponding to the delay time of the reflected wave signal is extracted. For example, the difference frequency between the frequency of the transmitted signal (transmitted frequency modulated wave) and the frequency of the received signal (received frequency modulated wave) is obtained as the beat frequency (or beat signal).

[0087] The signal processing unit 206 of each antenna system processing unit 201-z (where z=1 to Na) has an A / D conversion unit 207, a beat frequency analysis unit 208, and a Doppler analysis unit 210. Note that the Doppler analysis unit 210 may include, for example, a Doppler analysis unit 210-1 and a Doppler analysis unit 210-2 corresponding to a first chirp signal and a second chirp signal having different center frequencies, respectively.

[0088] The signal output from the LPF 205 (for example, a beat signal) is converted into discrete sample data by the A / D converter 207 in the signal processor 206, which is discretely sampled.

[0089] The beat frequency analysis unit 208 analyzes the transmission period T r For each time, N obtained in a given time range (range gate) data The discrete sample data are subjected to FFT processing. Here, the range gate is set to the frequency sweep time T sw (q) is set. Here, for example, q=1 or 2, and when q=1, it represents the frequency sweep time of the first chirp signal, and when q=2, it represents the frequency sweep time of the second chirp signal. As a result, the signal processing unit 206 outputs a frequency spectrum in which a peak appears at the beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave). Note that during FFT processing, the beat frequency analysis unit 208 may multiply by a window function coefficient such as a Han window or a Hamming window. Using the window function coefficient makes it possible to suppress side lobes that occur around the beat frequency peak.

[0090] Here, the beat frequency response output from the beat frequency analysis unit 208 in the zth signal processing unit 206 obtained by transmitting the mth chirp pulse of the qth chirp signal is referred to as RFT z,q (f b , m), where f b represents the beat frequency index, which corresponds to the FFT index (bin number). For example, f b =0,~,N data / 2-1, z=1,~,Na, m=1,~,NC where q=1 or 2. The beat frequency index f b The smaller the beat frequency, the shorter the delay time of the reflected wave signal (for example, the closer the distance to the target).

[0091] Also, the beat frequency index f b is calculated by the following equation (1): b ) can be transformed into the beat frequency index f b Let "distance index f b " is called.

number

[0092] where B w represents the frequency sweep bandwidth of the chirp signal, and C0 represents the speed of light. Also, in equation (1), C0 / 2B w represents the distance resolution. In the following, distance resolution ΔR=C0 / 2B w It is expressed as:

[0093] The output switching unit 209 selectively switches the output of the beat frequency analysis unit 208 to one of the two Doppler analysis units 210 in accordance with the transmission period of the first chirp signal or the transmission period of the second chirp signal based on the control signal output from the signal generation control unit 104. For example, the output switching unit 209 selectively switches the output of the beat frequency analysis unit 208 to one of the two Doppler analysis units 210 in accordance with the transmission period T r1 The output of the beat frequency analysis unit 208 in this case is output to the Doppler analysis unit 210-1. In addition, for example, the output switching unit 209 outputs the output of the beat frequency analysis unit 208 in this case to the Doppler analysis unit 210-1. r2 The output of the beat frequency analysis unit 208 in the above step is output to the Doppler analysis unit 210-2.

[0094] The q-th Doppler analyzer 210 (also referred to as Doppler analyzer 210-q) is a Doppler analyzer for the N C Beat frequency response RFT obtained by transmitting a single chirp pulse z,q (fb , 1), RFT z,q (f b , 2), ~, RFT z,q (f b , N C ) to find the distance index f b For example, the qth Doppler analyzer 210 may estimate the Doppler frequency from a reflected wave signal of the qth chirp signal reflected by a target.

[0095] For example, N c If is a power of 2, FFT processing can be applied in Doppler analysis. In this case, the FFT size is N c The maximum Doppler frequency at which aliasing does not occur, derived from the sampling theorem, is ±1 / (2T rs ) and the Doppler frequency index f s The Doppler frequency interval is 1 / (N c ×T rs ) and the Doppler frequency index f s The range of f s = -N c / 2, ~, 0, ~, N c / 2-1.

[0096] In the following, as an example, c The case where N is a power of 2 will be explained. c If is not a power of 2, for example, by including zero-padded data, FFT processing can be performed with a data size that is a power of 2. Furthermore, the Doppler analysis unit 210 may multiply by a window function coefficient such as a Han window or a Hamming window during FFT processing. Applying a window function can suppress side lobes that occur around the beat frequency peak.

[0097] For example, the output VFT of the q-th Doppler analyzer 210 of the z-th signal processor 206 z,q (f b , f s ) is shown in the following formula (2), where j is the imaginary unit, z=1 to Na, and q=1, 2.

number

[0098] The processing in each component of the signal processing unit 206 has been described above.

[0099] In FIG. 2, the CFAR unit 211 performs CFAR processing (for example, adaptive threshold determination) using the outputs from the Doppler analysis units 210 of the first to Na-th signal processing units 206, and calculates a distance index f that gives a local peak signal. b_cfar and the Doppler frequency index f s_cfar 2, the CFAR unit 211 may include a first CFAR unit 211 (also referred to as a CFAR unit 211-1) that performs CFAR processing using the output of the first Doppler analysis unit 210, and a second CFAR unit 211 (also referred to as a CFAR unit 211-2) that performs CFAR processing using the output of the second Doppler analysis unit 210.

[0100] The q-th CFAR unit 211 (q=1, 2) calculates the output VFT of the q-th Doppler analyzer 210 of the first to Na-th signal processors 206 as shown in the following equation (3), for example. 1,q (f b , f s ), VFT 2,q (f b , f s ), ~, VFT Na,q (f b , f s ) are power-added, and two-dimensional CFAR processing consisting of a distance axis and a Doppler frequency axis (corresponding to relative velocity) or CFAR processing combining one-dimensional CFAR processing is performed. For the two-dimensional CFAR processing or the CFAR processing combining one-dimensional CFAR processing, the processing disclosed in Non-Patent Document 2 may be applied, for example.

number

[0101] The qCFAR unit 211 adaptively sets a threshold value and calculates the distance index f th at which the received power is greater than the threshold value. b_cfar (q), the Doppler frequency index f s_cfar (q), and received power information PowerFT(f b_cfar (q), f s_cfar (q)) is output to the q-th Doppler demultiplexing unit 212.

[0102] The Doppler demultiplexing unit 212 may include a first Doppler demultiplexing unit 212 (also referred to as Doppler demultiplexing unit 212-1) that performs Doppler demultiplexing processing using the outputs of the first Doppler analysis unit 210 and the first CFAR unit 211, and a second Doppler demultiplexing unit 212 (also referred to as Doppler demultiplexing unit 212-2) that performs Doppler demultiplexing processing using the outputs of the second Doppler analysis unit 210-2 and the second CFAR unit 211.

[0103] The q-th Doppler demultiplexing unit 212 (q=1, 2) receives information (for example, a distance index f b_cfar (q), the Doppler frequency index f s_cfar (q), and received power information PowerFT(f b_cfar (q), f s_cfar Based on the Doppler multiplexing signal (hereinafter referred to as "Doppler multiplexed signal"), the qth Doppler demultiplexing unit 212 uses the output from the qth Doppler analysis unit 210 to separate the transmission signals (e.g., reflected wave signals corresponding to the transmission signals) transmitted from each transmitting antenna 106 from the Doppler multiplexed transmitted signal (hereinafter referred to as "Doppler multiplexed signal"). The qth Doppler demultiplexing unit 212 outputs, for example, information about the separated signals to the Doppler determination unit 213 and the direction estimation unit 214. The information about the separated signals includes, for example, a distance index f corresponding to the separated signal. b_cfar (q), and the Doppler frequency index (hereinafter also referred to as separation index information) (f demul_Tx#1 (q), f demul_Tx#2 (q), …, f demul_Tx#Nt In addition, the q-th Doppler demultiplexing unit 212 outputs the output from the q-th Doppler analyzing unit 210 to the direction estimating unit 214.

[0104] An example of the operation of the qth Doppler demultiplexing unit 212 will be described below together with the operation of the Doppler shift unit 105.

[0105] [How to set the Doppler shift amount] First, an example of a method for setting the amount of Doppler shift imparted in the Doppler shifter 105 will be described.

[0106] The Doppler shift units 105-1 to 105-Nt apply different Doppler shift amounts DOP to the chirp signals input to each unit. n In one embodiment of the present disclosure, the Doppler shift amount DOP is given between the Doppler shift units 105-1 to 105-Nt (for example, between the transmitting antennas 106-1 to 106-Nt). n The intervals (Doppler shift intervals) are not equal, but are set so that at least one Doppler interval is different.

[0107] For example, the n-th Doppler shift unit 105 generates different Doppler shift amounts DOP for the m-th and q-th chirp signals input. n The phase rotation φ n (m) and output. As a result, different Doppler shift amounts are assigned to the transmission signals transmitted from the multiple transmission antennas 106. For example, in one embodiment, the Doppler multiplexing number N DM =Nt, where m=1 to N C where n is an integer from 1 to Nt, and q is 1 or 2.

[0108] In addition, the q-th Doppler analysis unit 210 calculates a Doppler frequency f d The range is -1 / (2T rs ) ≦ f d <1 / (2T rs )

[0109] From this, if the Doppler shift intervals for the transmission signals transmitted from the Nt transmission antennas 106 are equal to 1 / (Nt×Trs ) the phase rotation φ n (m) is expressed by the following equation (4).

number

[0110] Here, φ0 is the initial phase, and Δφ0 is the reference Doppler shift phase. Also, round(x) is a round function that outputs an integer value rounded off for a real value x. Note that round(N C / N t ) is introduced for the purpose of making the amount of phase rotation an integer multiple of the Doppler frequency interval in the Doppler analysis unit 210.

[0111] For example, if the phase rotation φ shown in Equation (4) n When (m) is used, the intervals of phase rotation between the transmitted signals given to the m-th q-th chirp signal are all equal, and are 2πround(N C / N t ) / N C This becomes:

[0112] As an example, in equation (4), Nt=2, Δφ0=0, φ0=0, and the phase rotation φ n When (m) is added, the Doppler shift is DOP1=0, DOP2=-1 / (2T rs )

[0113] For example, the intervals of the Doppler shift amounts imparted to the transmission signals transmitted from the multiple transmission antennas 106 are set to be equal intervals in the Doppler frequency range (for example, a Doppler frequency range in which aliasing does not occur) in the radar device 10 (radar receiver 200). For example, the intervals of the Doppler shift amounts imparted to the transmission signals transmitted from Nt=2 transmission antennas 106 are set to be equal intervals in the Doppler frequency range in which aliasing does not occur (for example, −1 / (2T rs ) ≦ f d <1 / (2T rs )) divided by the number of transmitting antennas 106 (for example, Nt=2) (in the above example, 1 / (2Trs )) Therefore, the Doppler interval between Doppler peak P1 and Doppler peak P2 is set to 1 / (2T rs )

[0114] FIG. 5 shows a case where DOP1=0 and DOP2=−1 / (2T rs 2 shows an example of a Doppler peak obtained by Doppler analysis (FFT) in the Doppler analysis unit 210 when the Doppler shift amount of

[0115] As shown in Figure 5, the Doppler frequency of one target to be measured (target doppler) f d_TargetDoppler For this reason, Nt (Nt=2 in FIG. 5) Doppler peaks occur.

[0116] As an example, in FIG. 5, the Doppler frequency f d_TargetDoppler = −1 / (4T rs ) and f d_TargetDoppler = 1 / (4T rs ) the positional relationship between the Doppler peak that occurs when a reflected wave signal is received in response to a transmission signal transmitted from transmitting antenna Tx#1 and the Doppler peak that occurs when a reflected wave signal is received in response to a transmission signal transmitted from transmitting antenna Tx#2 is compared.

[0117] <Doppler frequency of target f d_TargetDoppler =-1 / (4T rs )> f d_TargetDoppler =-1 / (4T rs ), as shown in FIG. 5, the Doppler peak that occurs when a reflected wave signal is received from the transmitting antenna Tx#2 is output as a peak (P2A) of the aliased signal in the FFT. d_TargetDoppler =1 / (4T rs), as shown in FIG. 5, the positional relationship between the Doppler peak (P1) generated when a reflected wave signal is received in response to a transmission signal from the transmitting antenna Tx#1 and the Doppler peak (P2A) of the folded signal is as follows. The Doppler interval between the Doppler peak (P1) and the Doppler peak (P2A) is 1 / (2T rs ) Note that the Doppler peak (P2') is the signal before aliasing, but it does not actually exist in the FFT output.

[0118] <Doppler frequency of target f d_TargetDoppler =1 / (4T rs )> f d_TargetDoppler =1 / (4T rs ), as shown in FIG. 5, the positional relationship between the Doppler peak (P1) generated when a reflected wave signal is received from the transmission signal from the transmission antenna Tx#1 and the Doppler peak (P2) generated when a reflected wave signal is received from the transmission antenna Tx#2 is as follows. The Doppler interval between the Doppler peak (P1) and the Doppler peak (P2) is 1 / (2T rs )

[0119] Thus, f d_TargetDoppler =‐1 / (4T rs ) and f d_TargetDoppler =1 / (4T rs ), the Doppler interval between the Doppler peak (P1) corresponding to the transmitting antenna Tx#1 and the Doppler peak (P2 or P2A) corresponding to the transmitting antenna Tx#2 is 1 / (2T rs ) Therefore, f d_TargetDoppler =‐1 / (4T rs ) and 1 / (4T rs ), the positional relationship between the Doppler peaks corresponding to Tx#1 and Tx#2 cannot be distinguished, and ambiguity occurs. Therefore, in the example shown in FIG. 5, the Doppler frequency range of the target where ambiguity does not occur is, for example, −1 / (4T rs ) ≦ f d_TargetDoppler < 1 / (4T rs )

[0120] 6, the Doppler shift unit 105 according to an embodiment of the present disclosure sets a Doppler shift amount that makes the Doppler multiplexing intervals uneven. For example, the Doppler shift unit 105 may impart Doppler shift amounts at intervals that unevenly divide the Doppler frequency range that is the target for determining the number of times the Doppler frequency is folded back. For example, the Doppler shift unit 105 imparts a Doppler shift amount DOP to the transmission signal transmitted from the transmission antenna 106. n (or phase rotation φ n (m)) have at least one different interval.

[0121] Also, for example, the Doppler shift unit 105 may set the intervals of the Doppler shift amounts applied to the transmission signals transmitted from the Nt transmission antennas 106 as large as possible, and may set the phase rotation φ n (m) Doppler shift DOP so that at least one interval is different n This improves the separation performance of Doppler multiplexing.

[0122] For example, the n-th Doppler shift unit 105 generates a Doppler shift amount DOP that differs between the Doppler shift units for the m-th input first chirp signal or second chirp signal. n The phase rotation φ as shown in the following equation (5) n (m) is assigned.

number

[0123] Here, A is a coefficient that gives the positive or negative polarity of 1 or -1. Also, δ is an integer equal to or greater than 1. Note that round(N C The term (2π / Nt+δ) is introduced to make the phase rotation amount an integer multiple of the Doppler frequency interval in the Doppler analysis unit 210. However, the present invention is not limited to this, and the term (2π / Nt+δ) in equation (5) can be used. C )×round(N C Instead of the term 2π / (Nt+δ), 2π / (Nt+δ) may be used.

[0124] For example, the radar device 10 performs unequal Doppler multiplexing on the first chirp signal and the second chirp signal at the same Doppler multiplexing interval.

[0125] As an example, in equation (5), Nt=2, Δφ0=0, φ0=0, A=1, δ=1, N C is a multiple of 3 and the phase rotation φ n When (m) is added, the Doppler shift amount is DOP1=0, DOP2=1 / (3T rs )

[0126] FIG. 6 shows the relationship between DOP1=0 and DOP2=1 / (3T) for the transmission signals transmitted from Nt=2 transmission antennas 106 (hereinafter referred to as Tx#1 and Tx#2). rs 2 shows an example of a Doppler peak obtained by Doppler analysis in the Doppler analysis unit 210 when the Doppler shift amount of

[0127] As shown in Figure 6, the Doppler frequency of one target to be measured (target doppler) f d_TargetDoppler For this reason, Nt (Nt=2 in FIG. 6) Doppler peaks occur.

[0128] As an example, FIG. 6 shows the Doppler frequency f of the target to be measured in the output of the Doppler analysis unit 210. d_TargetDoppler = −1 / (4T rs ) and f d_TargetDoppler = 1 / (4T rs ) the positional relationship between the Doppler peak that occurs when a reflected wave signal is received for a transmission signal transmitted from transmitting antenna Tx#1 and the Doppler peak that occurs when a reflected wave signal is received for a transmission signal transmitted from transmitting antenna Tx#2 is compared.

[0129] <Doppler frequency of target f d_TargetDoppler =‐1 / (4T rs )> f d_TargetDoppler =‐1 / (4T rs), as shown in FIG. 6, the positional relationship between the Doppler peak (P1) generated when a reflected wave signal is received from the transmission signal from the transmission antenna Tx#1 and the Doppler peak (P2) generated when a reflected wave signal is received from the transmission antenna Tx#2 is as follows. The Doppler interval between the Doppler peak P1 and the Doppler peak P2 is 1 / (3T rs )

[0130] <Doppler frequency of target f d_TargetDoppler = 1 / (4T rs )> f d_TargetDoppler = 1 / (4T rs ), as shown in FIG. 6, the Doppler peak that occurs when a reflected wave signal is received from the transmitting antenna Tx#2 is output as a peak (P2A) of the aliased signal in the FFT. d_TargetDoppler = 1 / (4T rs ), the positional relationship is between the Doppler peak (P1) that occurs when a reflected wave signal is received in response to a transmission signal from the transmitting antenna Tx#1 and the Doppler peak (P2A) of the above-mentioned folded signal. The Doppler interval between the Doppler peak (P1) and the peak (P2A) is 2 / (3T rs )

[0131] As shown in Figure 6, the target Doppler frequency f d_TargetDoppler = −1 / (4T rs ) and f d_TargetDoppler = 1 / (4T rs ), the positional relationship between the Doppler peak (P1) corresponding to the transmitting antenna Tx#1 and the Doppler peak (P2 or P2A) corresponding to the transmitting antenna Tx#2 is different from each other.

[0132] Therefore, in the example shown in FIG. 6, the Doppler demultiplexing unit 212 detects the Doppler frequency f d_TargetDoppler =‐1 / (4T rs ) (for example, without wrapping) and f d_TargetDoppler =1 / (4T rs ) (for example, when there is wrapping) can be distinguished.

[0133] For example, if the assumed target Doppler frequency is -1 / (2T rs ) ≦ f d_TargetDoppler < 1 / (2T rs ), the Doppler demultiplexing unit 212 detects the Doppler frequency f d_TargetDoppler = -1 / (4T rs ), it can be determined that the signal does not contain a folded signal. d_TargetDoppler = -1 / (4T rs ), the Doppler demultiplexing unit 212 can determine that the Doppler peaks containing no aliasing signals and having the smallest frequency are reflected wave signals corresponding to the transmission signals from the transmitting antennas Tx#1 and Tx#2, respectively.

[0134] Also, for example, if the assumed target Doppler frequency is -1 / (2T rs ) ≦ f d_TargetDoppler < 1 / (2T rs ), the Doppler demultiplexing unit 212 detects the Doppler frequency f d_TargetDoppler = 1 / (4T rs ), it can be determined that a folded Doppler peak (e.g., P2A) is included, and the Doppler frequency f d_TargetDoppler = 1 / (4T rs ) can be determined. For example, f shown in Figure 6 d_TargetDoppler = 1 / (4T rs ), a return signal (P2A) is included, so the Doppler demultiplexing unit 212 determines that the interval between Doppler peaks is 2 / (3T rs 6, it can be determined that the higher Doppler peak is the reflected wave signal corresponding to transmitting antenna Tx#1, and the lower Doppler peak is the reflected wave signal corresponding to transmitting antenna Tx#2. Note that P1' and P2' are shown in Fig. 6 for ease of explanation, but do not actually exist in the output of the Doppler analysis unit 210.

[0135] Next, as another example, in FIG. 6, the Doppler frequency f d_TargetDoppler = −1 / (2T rs) and f d_TargetDoppler = 1 / (2T rs ) the positional relationship between the Doppler peak that occurs when a reflected wave signal is received for a transmission signal transmitted from transmitting antenna Tx#1 and the Doppler peak that occurs when a reflected wave signal is received for a transmission signal transmitted from transmitting antenna Tx#2 is compared.

[0136] <Doppler frequency of target f d_TargetDoppler =‐1 / (2T rs )> f d_TargetDoppler =‐1 / (2T rs ), as shown in FIG. 6, the positional relationship between the Doppler peak (P1) generated when a reflected wave signal is received from the transmission signal from the transmission antenna Tx#1 and the Doppler peak (P2) generated when a reflected wave signal is received from the transmission antenna Tx#2 is as follows. The Doppler interval between the Doppler peak (P1) and the Doppler peak (P2) is 1 / (3T r )

[0137] <Doppler frequency of target f d_TargetDoppler =1 / (2T rs )> f d_TargetDoppler =1 / (2T rs 6, the Doppler peak generated when a reflected wave signal from the transmission signal from transmitting antenna Tx#1 is received is output as a Doppler peak (P1A) of the aliased signal by FFT, and the Doppler peak generated when a reflected wave signal from the transmission signal from transmitting antenna Tx#2 is received is output as a Doppler peak (P2A) of the aliased signal by FFT. Therefore, the positional relationship between the Doppler peak (P1A) generated when a reflected wave signal from the transmission signal from transmitting antenna Tx#1 is received and the Doppler peak (P2A) of the aliased signal is as follows. The Doppler interval between the Doppler peak (P1A) and the Doppler peak (P2A) is 1 / (3Tr).

[0138] Thus, the target Doppler frequency f d_TargetDoppler =‐1 / (2Trs ) and f d_TargetDoppler =1 / (2T rs ), the Doppler interval between the Doppler peak (P1) corresponding to the transmitting antenna Tx#1 and the Doppler peak (P2 or P2A) corresponding to the transmitting antenna Tx#2 is 1 / (3T rs ) Therefore, f d_TargetDoppler =‐1 / (2T rs ) and f d_TargetDoppler =1 / (2T rs ), the positional relationship between the Doppler peaks corresponding to Tx#1 and Tx#2 cannot be distinguished, resulting in ambiguity. Therefore, in the example shown in FIG. 6, the Doppler frequency range of the target in which ambiguity does not occur in the Doppler demultiplexing unit 212 is, for example, −1 / (2T rs ) ≦ f d_TargetDoppler < 1 / (2T rs )

[0139] Therefore, with the Doppler shift setting in FIG. 6, the Doppler frequency range of the target where ambiguity does not occur can be expanded by Nt times (for example, twice in FIG. 6) compared to time division multiplexing or Doppler multiplexing where the Doppler shift amount is set at equal intervals (for example, see FIG. 5).

[0140] In this embodiment, a method will be described in which the Doppler frequency range of a target in which no ambiguity occurs is further expanded by processing by the Doppler determination unit 213, which will be described later.

[0141] Next, an example of a method for separating signals corresponding to each transmitting antenna 106 in the Doppler demultiplexing unit 212 will be described.

[0142] As an example, the operation of the Doppler demultiplexing unit 212 when Nt=2 will be described.

[0143] In the following, as an example, the phase rotation φ shown in Equation (5) is used in the Doppler shifter 105. n In the following, as an example, Δφ0=0, φ0=0, δ=1, N Cis a multiple of 3. When A=1, the Doppler shift amount for each transmitting antenna 106 is DOP1=0, DOP2=1 / (3T r ), and when A=-1, the Doppler shift amounts for each transmitting antenna 106 are DOP1=0, DOP2=-1 / (3T r )

[0144] In this case, the q-th Doppler demultiplexing unit 212 detects a peak (distance index f b_cfar (q) and the Doppler frequency index f s_cfar (q)) is used to separate the Doppler multiplexed signals.

[0145] For example, the q-th Doppler demultiplexing unit 212 uses the distance index f b_cfar (q) is the same as multiple Doppler frequency indexes f s_cfar For (q), it is determined which of the transmission signals transmitted from the transmitting antennas Tx#1 to Tx#Nt the reflected wave signal corresponds to. The Doppler demultiplexing unit 212 separates and outputs the reflected wave signal for each of the determined transmitting antennas Tx#1 to Tx#Nt.

[0146] In the following, the distance index f b_cfar (q) is the same as multiple Doppler frequency indexes f s_cfar We will explain the operation when there are Ns (q). For example, f s_cfar (q)∈{fd #1 ,fd #2 …,fd #Ns}

[0147] Here, one target Doppler frequency f is obtained by the Doppler shift amounts DOP1 and DOP2 given to the transmission signals transmitted from the transmitting antennas Tx#1 and Tx#2, respectively. d_TargetDopplerFor this, Nt=2 Doppler peaks occur. The Doppler index interval corresponding to the Doppler interval between these Doppler peaks is calculated by the difference between the phase rotation φ1(m) for the transmitting antenna Tx#1 and the phase rotation φ2(m) for the transmitting antenna Tx#2, as shown in the following equation (6), round (N c In addition, when aliasing signals are included, the Doppler index interval corresponding to the Doppler interval between Doppler peaks is N c -round(N c / (Nt+1)).

number

[0148] The q-th Doppler demultiplexing unit 212 uses, for example, a distance index f b_cfar (q) is the same as multiple Doppler frequency indexes f s_cfar (q) ∈{fd #1 ,fd #2 …,fd #Ns}, the q-th Doppler demultiplexing unit 212 calculates a Doppler index interval round(N c / (Nt+1)), or the Doppler index interval (N c -round(N c / (Nt+1))).

[0149] The q-th Doppler demultiplexing unit 212 performs the following processing based on the result of the above-mentioned search.

[0150] (1) The index interval corresponding to the interval of the Doppler shift amount when the aliasing signal is not included is round(N c / (Nt+1)), the q-th Doppler demultiplexing unit 212 demultiplexes the Doppler frequency index pair (for example, fd#p , fd #q (represented as) as the separation index information (f demul_Tx#1 (q), f demul_Tx#2 (q)) of the Doppler multiplex signal.

[0151] Here, when the relationship of the Doppler shift amounts for the transmission antennas Tx#1 and Tx#2 is DOP1 < DOP2, the q-th Doppler multiplex separation unit 212 determines the larger one of fd #p , fd #q as the Doppler frequency index f demul_Tx#2 (q) corresponding to Tx#2, and the lower one as the Doppler frequency index f demul_Tx#1 (q) corresponding to Tx#1. On the other hand, when the relationship of the Doppler shift amounts for the transmission antennas Tx#1 and Tx#2 is DOP1 > DOP2, the Doppler multiplex separation unit 212 determines the larger one of fd #p , fd #q as the Doppler frequency index f demul_Tx#1 (q) corresponding to Tx#1, and the lower one as the Doppler frequency index f demul_Tx#2 (q) corresponding to Tx#2.

[0152] (2) Index interval N corresponding to the interval of the Doppler shift amounts when the folded signal is included c - round(N c / (Nt + 1)) coincides with the Doppler frequency index, the q-th Doppler multiplex separation unit 212 outputs the pair of those Doppler frequency indices (for example, fd #p , fd #q ) as the separation index information (f demul_Tx#1 (q), f demul_Tx#2 (q)) of the Doppler multiplex signal.

[0153] Here, when the relationship of the Doppler shift amounts for the transmission antennas Tx#1 and Tx#2 is DOP1 < DOP2, the q-th Doppler multiplex separation unit 212 determines the larger one of fd #p , fd #q as the Doppler frequency index f demul_Tx#1(q), and the lower one is the Doppler frequency index f demul_Tx#2 On the other hand, if the Doppler shift amounts for the transmitting antennas Tx#1 and Tx#2 are in the relationship of DOP1>DOP2, the q-th Doppler demultiplexing unit 212 determines that fd #p ,fd #q The larger of the two is the Doppler frequency index f demul_Tx#2 (q), and the lower one is the Doppler frequency index f demul_Tx#1 The answer is (q).

[0154] (3) The index interval corresponding to the interval of the Doppler shift amount when the aliasing signal is not included is round(N c / (Nt+1)) and the index interval N corresponding to the interval of the Doppler shift amount when the aliasing signal is included. c -round(N c / (Nt+1)), the q-th Doppler demultiplexing unit 212 determines that the generated Doppler peak is a noise component. In this case, the Doppler demultiplexing unit 212 determines that the Doppler frequency index that matches the Doppler multiplexed signal (f demul_Tx#1 (q), f demul_Tx#2 (q)) may be omitted.

[0155] In this manner, the q-th Doppler demultiplexing unit 212 can demultiplex the Doppler multiplexed signal.

[0156] Although an example of the operation of Doppler multiplexing when Nt=2 has been described, the number of transmitting antennas Nt is not limited to 2 and may be 3 or more. Below, as another example, the operation of the radar device 10 when Nt=3 will be described.

[0157] In the following, as an example, the phase rotation φ shown in Equation (5) is used in the Doppler shifter 105. nIn the following, as an example, Δφ0=0, φ0=0, A=1, and δ=1. In this case, the Doppler shift amounts for each transmitting antenna 106 are DOP1=0, DOP2=1 / (4T rs ), DOP3=-1 / (2T rs )

[0158] When such a Doppler shift amount is used, for example, as shown in FIG. 7, one target Doppler frequency f d_TargetDoppler Nt Doppler peaks (three in Fig. 7) occur for this frequency. Fig. 7 is a diagram showing changes in Nt=3 Doppler peaks when the horizontal axis indicates the target Doppler frequency and the vertical axis indicates the output of the q-th Doppler analysis unit 210 (FFT).

[0159] < Target Doppler frequency 0 ≦ f d_TargetDoppler <1 / (2T rs )> As shown in FIG. 7, the Doppler interval between the Doppler peak (solid line) generated when a reflected wave signal is received from the transmission signal from the transmission antenna Tx#1 and the Doppler peak (dashed line) generated when a reflected wave signal is received from the transmission signal from the transmission antenna Tx#3 is 1 / (2T rs ) In this case, 0≦f d_TargetDoppler <1 / (4T rs ) does not contain any reflected signals for any of the transmitting antennas Tx#1, Tx#2, and Tx#3, so the qth Doppler demultiplexing unit 212 can determine from the low frequency Doppler peaks that they are reflected wave signals for the transmitted signals from the transmitting antennas Tx#3, Tx#1, and Tx#2, respectively.

[0160] Also, in this case, 1 / (4T rs )≦f d_TargetDoppler <1 / (2T rs ) contains a return signal for Tx#2. Therefore, the q-th Doppler demultiplexing unit 212 detects that the interval between Doppler peaks is 1 / (2T rs), it can be determined that the higher Doppler peak (solid triangle) is the reflected wave signal corresponding to transmitting antenna Tx#1, the lower Doppler peak (solid square) is the reflected wave signal corresponding to transmitting antenna Tx#3, and the remaining Doppler peak is the reflected wave signal from transmitting antenna Tx#2.

[0161] <Target Doppler frequency is -1 / (2T rs )≦ f d_TargetDoppler <In case of 0> As shown in FIG. 7, since a return signal is included for Tx#1, the Doppler interval between the Doppler peak (solid line) generated when a reflected wave signal for the transmission signal from the transmission antenna Tx#1 is received and the Doppler peak (dotted line) generated when a reflected wave signal for the transmission signal from the transmission antenna Tx#2 is received is 1 / (4T rs ) The Doppler interval between the Doppler peak (dotted line) generated when a reflected wave signal is received from the transmission signal from the transmission antenna Tx#2 and the Doppler peak (constant dashed line) generated when a reflected wave signal is received from the transmission signal from the transmission antenna Tx#3 is 1 / (4T rs )

[0162] In this case, since the signal includes a return signal for transmitting antenna Tx#1, the qth Doppler multiplexing separation unit 212 can determine from the low frequency Doppler peaks that they are reflected wave signals for the transmitted signals from transmitting antennas Tx#1, Tx#2, and Tx#3, respectively.

[0163] Therefore, in the example shown in FIG. 7, the Doppler frequency range of the target where no ambiguity occurs is, for example, −1 / (2T rs ) ≦ f d_TargetDoppler <1 / (2T rs )

[0164] Next, an example of a method for separating signals corresponding to each transmitting antenna 106 in the q-th Doppler demultiplexing unit 212 will be described.

[0165] In the following, as an example, the phase rotation φ shown in Equation (5) is used in the Doppler shifter 105. n In the following, as an example, Nt=3, Δφ0=0, φ0=0, δ=1, N C is a multiple of 3. When A=1, the Doppler shift amount for each transmitting antenna 106 is DOP1=0, DOP2=1 / (4T rs ), DOP3=1 / (2T rs ) =-1 / (2T rs ), and when A=-1, the Doppler shift amounts for each transmitting antenna 106 are DOP1=0, DOP2=-1 / (4T rs ), DOP3=-1 / (2T rs )

[0166] The q-th Doppler demultiplexing unit 212 receives a peak (distance index f b_cfar (q) and the Doppler frequency index f s_cfar (q)) is used to separate the Doppler multiplexed signals.

[0167] For example, the q-th Doppler demultiplexing unit 212 uses the distance index f b_cfar (q) is the same as multiple Doppler frequency indexes f s_cfar For (q), it is determined which of the transmission signals transmitted from the transmitting antennas Tx#1 to Tx#Nt the reflected wave signal corresponds to. The qth Doppler demultiplexing unit 212 separates and outputs the reflected wave signal for each of the determined transmitting antennas Tx#1 to Tx#Nt.

[0168] In the following, the distance index f b_cfar (q) is the same as multiple Doppler frequency indexes f s_cfar We will explain the operation when there are Ns (q). For example, f s_cfar (q)∈{fd #1 ,fd #2 …,fd #Ns}

[0169] For example, the q-th Doppler multiplex separation unit 212 calculates the Doppler line index interval for a plurality of Doppler frequency indices f b_cfar (q) that are the same. s_cfar (q) ∈ {fd #1 , fd #2 …, fd #Ns}. Then, the q-th Doppler multiplex separation unit 212 searches for a combination of Doppler frequency indices where the interval between two Doppler line indices when the three Doppler frequency indices are viewed in ascending order matches the index interval corresponding to the interval of the Doppler shift amount when there is no folded signal. Alternatively, the q-th Doppler multiplex separation unit 212 searches for a combination of Doppler frequency indices where the interval between two Doppler line indices when the three Doppler frequency indices are viewed in ascending order matches the index interval corresponding to the interval of the Doppler shift amount when there is a folded signal.

[0170] Based on the result of the above search, the q-th Doppler multiplex separation unit 212 performs the following processing.

[0171] (1) If there is a combination of Doppler frequency indices that does not include a folded signal and matches the index interval corresponding to the interval of the Doppler shift amount, the q-th Doppler multiplex separation unit 212 outputs the set of those Doppler frequency indices (for example, represented as fd #p1 , fd #p2 , fd #p3 ) as the separation index information (f demul_Tx#1 (q), f demul_Tx#2 (q), f demul_Tx#3 (q)) of the Doppler multiplex signal.

[0172] Here, when the relationship of the Doppler shift amounts for transmission antennas Tx#1 to Tx#3 is DOP3 < DOP1 < DOP2, the q-th Doppler multiplex separation unit 212 selects, from the larger ones among fd #p1 , fd #p2 , fd #p3 , the Doppler frequency indices f demul_Tx#2 (q) corresponding to Tx#2, Tx#1, and Tx#3 respectively.demul_Tx#1 (q), f demul_Tx#3 (q) is determined (when 0 ≤ f in FIG. 7 d_TargetDoppler <1 / (4T rs )). Also, when the Doppler shift amounts for transmission antennas Tx#1 to Tx#3 are in the relationship DOP1 > DOP2 > DOP3, the q-th Doppler multiplex separation unit 212 determines the Doppler frequency indices f #p1 , fd #p2 , fd #p3 from the larger ones among them, corresponding to Tx#1, Tx#2, and Tx#3 respectively, as the Doppler frequency index f demul_Tx#1 (q), f demul_Tx#2 (q), f demul_Tx#3 (q).

[0173] (2) If there is a combination of Doppler frequency indices that includes a folded signal and matches the index interval corresponding to the interval between the Doppler shift amounts, the q-th Doppler multiplex separation unit 21 outputs the set of those Doppler frequency indices (for example, fd #q1 , fd #q2 , fd #q3 represented as) as the separation index information (f demul_Tx#1 (q), f demul_Tx#2 (q), f demul_Tx#3 (q)) of the Doppler multiplex signal.

[0174] For example, when the Doppler shift amounts for transmission antennas Tx#1 to Tx#3 are in the relationship DOP3 < DOP1 < DOP2 and there is a combination of Doppler frequency indices where the Doppler frequency corresponding to DOP3 is the folded signal, the q-th Doppler multiplex separation unit 212 determines the Doppler frequency indices f #q1 , fd #q2 , fd #q3 from the larger ones among them, corresponding to Tx#3, Tx#2, and Tx#1 respectively, as the Doppler frequency index f demul_Tx#2 (q), f demul_Tx#1 (q), f demul_Tx#3 (q) (when -1 / (2T rs ) ≤ f d_TargetDoppler<0). Also, when the Doppler shift amounts for the transmission antennas Tx#1 to Tx#3 have a relationship of DOP1 > DOP2 > DOP3 and there is a combination of Doppler frequency indexes where the Doppler frequency corresponding to DOP3 becomes a folded signal, the q-th Doppler multiplex separation unit 212 determines fd #q1 , fd #q2 , fd #q3 Of these, the larger ones are f corresponding to Tx#3, Tx#1, and Tx#2 respectively demul_Tx#2 (q), f demul_Tx#3 (q), f demul_Tx#1 (q).<000​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Furthermore, when the Doppler shift amounts for the transmitting antennas Tx#1 to Tx#3 are in the relationship DOP1>DOP2>DOP3 and there is a combination of Doppler frequency indexes where the Doppler frequency corresponding to DOP1 becomes a aliasing signal, the q-th Doppler demultiplexing unit 212 calculates fd #u1 ,fd #u2 ,fd #u3 The larger of the f corresponds to Tx#2, Tx#3, and Tx#1, respectively. demul_Tx#3 (q), f demul_Tx#1 (q), f demul_Tx#2 The answer is (q).

[0178] (4) The q-th Doppler demultiplexing unit 212 determines that a Doppler peak corresponding to a Doppler frequency index that does not fall under any of the above (1), (2), and (3) is a noise component. In this case, the q-th Doppler demultiplexing unit 212 determines that a Doppler peak corresponding to a Doppler frequency index that does not fall under any of the above (1), (2), and (3) is a noise component. demul_Tx#1 (q), f demul_Tx#2 (q), f demul_Tx#3 (q)) may be omitted.

[0179] In this manner, the Doppler demultiplexing unit 212 can demultiplex the Doppler multiplexed signal.

[0180] In addition, the Doppler shift amount DOP given to the transmission signal n As an example of the phase rotation corresponding to n However, the phase rotation is the phase rotation φ shown in Equation (5). n (m) is not limited to this.

[0181] As another example, the n-th Doppler shift unit 105 calculates a Doppler shift amount DOP for the input m-th chirp signal (transmission signal) that is different from the case where equation (5) is used. n The phase rotation φ of the following equation (7) n (m) may be added. Note that round(N CThe term (2π / Nt+δ) is introduced to make the phase rotation amount an integer multiple of the Doppler frequency interval in the Doppler analysis unit 210. However, the present invention is not limited to this, and the term (2π / Nt+δ) in equation (7) can be used. C )×round(N C Instead of the term 2π / Nt, 2π / Nt may be used.

number

[0182] where dp n are components that make the phase rotation unevenly spaced in the Doppler frequency range. For example, dp1, dp2, ..., dp Nt -round(N C / Nt) / 2< dp n < round(N C The values ​​are in the range of round(N / Nt) / 2, and they are not all the same value, but contain at least one component with a different value. C / Nt) is introduced for the purpose of making the amount of phase rotation an integer multiple of the Doppler frequency interval in the Doppler analysis unit 210.

[0183] As an example, in equation (7), the phase rotation φ when Nt=2, Δφ0=0, φ0=0, A=1, dp1=0, and dp2=π / 5 is n When (m) is added, the Doppler shift amount is DOP1=0, DOP2=1 / (2T rs )+1 / (10T rs )=6 / (10T rs )=-4 / (10T rs )

[0184] FIG. 8 shows the results when Nt=2, DOP1=0, and DOP2=-4 / (10T) when the horizontal axis indicates the target Doppler frequency and the vertical axis indicates the output of the Doppler analysis unit 210 (FFT). rs ) is a graph showing the change in the Doppler peak. In this case, DOP1>DOP2.

[0185] <Target Doppler frequency is -1 / (10T rs )≦ fd_TargetDoppler <1 / (2T rs )> As shown in FIG. 8, the Doppler interval between the Doppler peak (solid line) generated when a reflected wave signal is received from a transmission signal from the transmission antenna Tx#1 and the Doppler peak (dotted line) generated when a reflected wave signal is received from a transmission signal from the transmission antenna Tx#2 is 4 / (10T rs )

[0186] In this case, neither of the transmitting antennas Tx#1 and Tx#2 includes a return signal. Therefore, the q-th Doppler demultiplexing unit 212 detects a Doppler peak interval of 4 / (10T rs ), it can be determined that the higher Doppler peak (solid triangle) is the reflected wave signal corresponding to transmitting antenna Tx#1, and the lower Doppler peak (solid square) is the reflected wave signal corresponding to transmitting antenna Tx#2.

[0187] <Target Doppler frequency is -1 / (2T rs )≦ f d_TargetDoppler < -1 / (10T rs )> As shown in FIG. 8, the Doppler interval between the Doppler peak (solid line) generated when a reflected wave signal is received from the transmission signal from the transmission antenna Tx#1 and the Doppler peak (dotted line) generated when a reflected wave signal is received from the transmission signal from the transmission antenna Tx#2 is 6 / (10T rs )

[0188] In this case, a return signal is included for Tx#2 (solid circle). Therefore, the q-th Doppler demultiplexing unit 212 can determine, for example, from the low-frequency Doppler peaks (dotted triangles) that they are reflected wave signals of the transmission signals from the transmitting antennas Tx#1 and Tx#2, respectively.

[0189] Therefore, in the example shown in FIG. 8, the Doppler frequency range of the target where no ambiguity occurs is, for example, −1 / (2T rs ) ≦ f d_TargetDoppler <1 / (2Trs )

[0190] The above has described an example of the operation of the Doppler demultiplexing unit 212. Note that, in the above description of the example of the operation of the Doppler demultiplexing unit 212, the radar device 10 has been described as performing unequal interval Doppler multiplexing on the first chirp signal and the second chirp signal at the same (unequally divided) Doppler multiplexing interval, but this is not limiting, and the radar device 10 may perform unequal interval Doppler multiplexing on the first chirp signal and the second chirp signal using different parameters, such as different (unequally divided) Doppler multiplexing intervals.

[0191] For example, when Nt=2, the Doppler shift amount for each transmitting antenna 106 is set to DOP1=0 and DOP2=1 / (3T r ), and for the second chirp signal, the Doppler shift amount for each transmitting antenna 106 is set to DOP1=0, DOP2=1 / (4T r ) and perform unequal interval Doppler multiplexing using parameters that result in different Doppler multiplexing intervals between the first chirp signal and the second chirp signal.

[0192] Alternatively, for example, when Nt=2, the Doppler shift amount for each transmitting antenna 106 is set to DOP1=0 and DOP2=1 / (3T r ), and for the second chirp signal, the Doppler shift amount for each transmitting antenna 106 is set to DOP1=1 / (4T r ), DOP2=-1 / (2T r ) and perform unequal interval Doppler multiplexing using parameters that result in different Doppler multiplexing intervals between the first chirp signal and the second chirp signal.

[0193] Even in such a case, the above-described operation can be applied because, in the radar receiving unit 200, the first chirp signal is processed by the first Doppler analysis unit 210 and the first Doppler demultiplexing unit 212, and the second chirp signal is processed independently by the second Doppler analysis unit 210 and the second Doppler demultiplexing unit 212. In this way, in the radar device 10, since each chirp signal is individually received and processed, it is not necessary to make the parameters for performing uneven Doppler multiplexing common to all chirp signals.

[0194] 2, the Doppler determination unit 213 determines the Doppler frequency corresponding to the Doppler peak based on the outputs of the first Doppler demultiplexing unit 212 and the second Doppler demultiplexing unit 212. For example, the Doppler determination unit 213 determines the Doppler frequency f d_TargetDoppler is the Doppler frequency range -1 / (2T rs ) ≦ f d_TargetDoppler <1 / (2T rs ), the Doppler detection range can be further expanded by determining the Doppler frequency of the target.

[0195] For example, the Doppler determination unit 213 determines the distance index f b_cfar (1) and f b_cfar (2) is common to the separation index information (f demul_Tx#1 (1), f demul_Tx#2 (1), ..., f demul_Tx#Nt (1)) and the separation index information (f demul_Tx#1 (2), f demul_Tx#2 (2), ...,f demul_Tx#Nt (2)) to obtain the Doppler frequency range -1 / (2T rs ) ≦ f d_TargetDoppler <1 / (2T rs ) and determine the Doppler frequency of the target including the Doppler frequency exceeding the Doppler frequency of the target.

[0196] The Doppler frequency determination in the Doppler determination unit 213 utilizes the fact that the center frequencies of the first chirp signal and the second chirp signal, which are radar transmission signals generated by the signal generation control unit 104 and the radar transmission signal generation unit 101, are different from each other.

[0197] The operating principle of the Doppler frequency determination process and an example of the operation of the Doppler determination unit 213 will be described below.

[0198] In the following, the Doppler determination unit 213 uses the distance index f b_cfar (1) and f b_cfar An example will be described in which processing is performed using separation index information of the Doppler multiplexed signals output from the first Doppler multiplex separation unit 212 and the second Doppler multiplex separation unit 212, which are common to (2). For this reason, the distance index will be referred to as "f b_cfar " (=f b_cfar (1)=f b_cfar (2)) is abbreviated.

[0199] For example, if the center frequency of the first chirp signal differs from the center frequency of the second chirp signal, the Doppler frequency of the reflected wave also changes. For example, if the radar device 10 is stationary and a target is moving toward the radar device 10 at a speed v, the Doppler frequency f observed using the first chirp signal will be d (1) is f d (1)=2v×f c (1) / C0, and the Doppler frequency f observed using the second chirp signal d (2) is f d (2)=2v×f c (2) / C0. Therefore, the relationship between the Doppler frequencies is f d (2) / f d (1)=f c (2) / f c (1). For example, f d (2) is f d (1) Center frequency ratio f c (2) / f c (1) can be calculated by multiplying (f d (2)=(fc (2) / f c (1))×f d (1)) where C0 represents the speed of light.

[0200] Also, for example, the Doppler frequency f d_TargetDoppler is the Doppler frequency range -1 / (2T rs ) ≦ f d_TargetDoppler <1 / (2T rs ), and the Doppler frequency estimate detected in the first Doppler analyzer 210 and the first Doppler demultiplexer 212 is assumed to exceed f d_VFT If (1), the target Doppler frequency f d_TargetDoppler Considering Doppler aliasing, is expressed by the following equation (8): al represents the number of Doppler aliasing and takes an integer value. f d_TargetDoppler = f d_VFT (1)+ n al / T rs (8)

[0201] Doppler fold count n al Since it is difficult to determine from the outputs of the first Doppler analysis unit 210 and the first Doppler demultiplexing unit 212, the conditions under which it can be determined using the outputs of the second Doppler analysis unit 210 and the second Doppler demultiplexing unit 212 are derived below. Here, the Doppler frequency observed using the second chirp signal is calculated by adding the center frequency ratio f c (2) / f c This is obtained by multiplying (1). f c (2) / f c (1) × f d_TargetDoppler = f c (2) / f c (1)×(f d_VFT (1)+ n al / T rs ) (9)

[0202] For example, the Doppler frequency observed using the second chirp signal is expressed as the Doppler fold count n al If =0, then f c (2) / fc (1) × f d_VFT (1), and the Doppler fold count is n al If =1, then f c (2) / f c (1)×(f d_VFT (1)+1 / T rs ) and the Doppler fold count is n al If =-1, then f c (2) / f c (1)×(f d_VFT (1)-1 / T rs ) The same applies to other Doppler aliasing times.

[0203] In this way, the number of Doppler folds n al The Doppler frequency difference due to the difference in c (2) / f c (1) / T rs are integer multiples of

[0204] where f c (2) / f c (1) / T rs and 1 / T, which is the aliasing frequency interval of the second Doppler analyzer 210. rs The difference between these is the Doppler frequency resolution Δf d If it is greater than the Doppler approximation number n al It is possible to detect (for example, determine) the Doppler frequency difference due to the difference.

[0205] Therefore, for example, the radar device 10 (for example, the signal generation control unit 104) determines the center frequency f of the first chirp signal so as to satisfy the condition (also referred to as the determination condition) shown in the following equation (10): c (1) and the center frequency f of the second chirp signal c (2) may be determined.

number

[0206] Here, for example, f c (2)>fc In the case of (1), f shown in equation (10) c (1) and f c The determination condition for (2) is expressed by the following equation (11).

number

[0207] Also, for example, f c (2) <f c In the case of (1), f shown in equation (10) c (1) and f c The determination condition for (2) is expressed by the following equation (12).

number

[0208] Furthermore, for example, the determination condition shown in the following equation (13) may be used, where α≧1.

number

[0209] Equation (13) is f c (2) / f c (1) / T rs and 1 / T, which is the aliasing frequency interval of the second Doppler analyzer 210. rs The difference between these is the Doppler frequency resolution Δf d The center frequency f that satisfies the condition that it is greater than an integer multiple α of c (1) and f c According to the determination condition shown in equation (13), the Doppler determination unit 213 compares the determination condition shown in equation (10) with the Doppler aliasing count n al For example, the determination condition shown in equation (13) can improve the determination accuracy even when there is noise influence, such as when the received signal level is low, compared to the determination condition shown in equation (10).

[0210] Here, for example, f c (2)>f c In the case of (1), f shown in equation (13) c (1) and f c The decision condition for (2) is expressed by the following equation (14).

number

[0211] Also, for example, f c (2) <f c In the case of (1), f shown in equation (13) c (1) and f c The decision condition for (2) is expressed by the following equation (15).

number

[0212] As an example, f c (1) = 78 GHz, f c (2)>f c (1), then, based on equation (14), for α=1 and Nc=128, f c (2) is set to be larger than 78.61 GHz, and f c (2) is set to be greater than 79.22GHz.

[0213] In this way, the center frequency f that satisfies any one of the determination conditions of Equation (10) to Equation (15) is c (1) and f c By setting (2), the Doppler determination unit 213 determines the Doppler frequency range −1 / (2T rs ) ≦ f d_TargetDoppler <1 / (2T rs ) is included (for example, when Doppler aliasing occurs), the Doppler frequency of the target can be determined.

[0214] For example, the Doppler determination unit 213 determines the distance index f output from the first Doppler demultiplexing unit 212 as b_cfarSeparation index information (f demul_Tx#1 (1), f demul_Tx#2 (1), ~f demul_Tx#Nt (1)), and the distance index f output from the second Doppler demultiplexing unit 212 b_cfar (2) Separation index information of Doppler multiplexed signals (f demul_Tx#1 (2), f demul_Tx#2 (2)~f demul_Tx#Nt (2)), the following Doppler determination process may be performed.

[0215] For example, the Doppler determination unit 213 determines the distance index f output from the first Doppler demultiplexing unit 212 as b_cfar Separation index information (f demul_Tx#1 (1), f demul_Tx#2 (1)~f demul_Tx#Nt (1)) is one, and the distance index f b_cfar (2) Separation index information of Doppler multiplexed signals (f demul_Tx#1 (2), f demul_Tx#2 (2)~f demul_Tx#Nt If (2)) is one, the following Doppler determination operation may be performed.

[0216] Further, the Doppler determination unit 213 determines, for example, the distance index f output from the first Doppler demultiplexing unit 212. b_cfar There are multiple pieces of separation index information for the Doppler multiplexed signal in (1), and the distance index f b_cfar In the case where there are multiple pieces of separation index information for the Doppler multiplexed signal in (2), the received powers indicated by these indexes may be compared, and the separation index information with similar received power levels may be associated as pairs.

[0217] Thereafter, the Doppler determination unit 213 may perform the following Doppler determination operation using the separation index information of the Doppler multiplexed signals output from the first Doppler multiplex separation unit 212 and the separation index information of the Doppler multiplexed signals output from the second Doppler multiplex separation unit 212, which are associated as a pair. For example, the Doppler determination unit 213 may sequentially perform the following Doppler determination operation for each associated pair of separation index information of the Doppler multiplexed signals output from the first Doppler multiplex separation unit 212 and separation index information of the Doppler multiplexed signals output from the second Doppler multiplex separation unit 212, and repeat the following operation for all pairs until it is completed.

[0218] An example of the Doppler determination operation in Doppler determination section 213 will now be described.

[0219] First, the Doppler determination unit 213 receives the distance index f output from the first Doppler demultiplexing unit 212. b_cfar Separation index information (f demul_Tx#1 (1), f demul_Tx#2 (1), ..., f demul_Tx#Nt Based on (1), the Doppler frequency of the target is within the Doppler frequency range -1 / (2T rs ) ≦f d_TargetDoppler <1 / (2T rs ) and the estimated Doppler frequency f d_VFT Calculate (1).

[0220] Here, the distance index f output from the first Doppler demultiplexing unit 212 is b_cfar Separation index information (f demul_Tx#1 (1), f demul_Tx#2 (1) ~f demul_Tx#Nt (1)) includes a component of a predetermined Doppler shift amount given to each transmitting antenna 106 in the radar transmitter 100. For example, the Doppler determination unit 213 calculates the Doppler frequency estimated value f d_VFT (1) may be calculated.

[0221] Similarly, the Doppler determination unit 213 determines the distance index f output from the second Doppler demultiplexing unit 212. b_cfar (2) Separation index information of Doppler multiplexed signals (f demul_Tx#1 (2), f demul_Tx#2 (2)~f demul_Tx#Nt (2)), the Doppler frequency of the target is within the Doppler frequency range -1 / (2T rs ) ≦f d_TargetDoppler <1 / (2T rs ) and the estimated Doppler frequency f d_VFT Calculate (2).

[0222] Here, the distance index f output from the second Doppler demultiplexing unit 212 is b_cfar (2) Separation index information of Doppler multiplexed signals (f demul_Tx#1 (2), f demul_Tx#2 (2)~f demul_Tx#Nt (2) includes a component of a predetermined Doppler shift amount given to each transmitting antenna 106 in the radar transmitter 100. For example, the Doppler determination unit 213 calculates the Doppler frequency estimated value f d_VFT (2) may be calculated.

[0223] Next, the Doppler determination unit 213 determines the Doppler aliasing number n that minimizes the following equation (16): al Calculate.

number

[0224] Here, the number of Doppler folds n al is an integer value, calculated within a range of integer values ​​that covers the Doppler frequency range of the expected target.

[0225] Also, f est (f d_VFT(1) , n al ) is expressed as the Doppler frequency estimate f d_VFT (1) is the Doppler fold count nal Doppler frequency (f d_VFT(1) +n al / T rs ) and calculate the center frequency f c To convert the observed Doppler frequency using the second chirp signal in (2), f c (2) / f c It represents a function that outputs a value multiplied by (1). For example, f est (f d_VFT(1) , n al ) is the Doppler frequency estimate f d_VFT represents the Doppler frequency estimate corresponding to the second chirp signal estimated based on (1).

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[0226] In equation (17), Fmod[x] is ±1 / 2T rs is a function for calculating the Doppler frequency taking into account the aliasing of the Doppler analysis unit 210, and x≧1 / (2T rs ), then nmod=floor((x-1 / (2T rs )) / T rs )+1 and calculate x - nmod / T rs Also, x<-1 / (2T rs ), Fmod[x] is nmod=ceil((|x|-1 / (2T rs )) / T rs ) and calculate x + nmod / T rs Here, floor(x) is the floor function, which outputs the largest integer value that does not exceed x. Also, ceil(x) is the ceiling function, which outputs the smallest integer value that exceeds x.

[0227] Hereafter, the number of Doppler folds n al Doppler frequency f when est (f d_VFT(1) , n al ) and the Doppler frequency estimate f d_VFT The number of Doppler aliasing n when the match (or degree of match, closeness) with (2) is the highestal (For example, the n al ) is the estimated Doppler aliasing number n alest " is written as ".

[0228] Next, an example of the above-mentioned Doppler determination operation will be described with reference to Fig. 9. In Fig. 9, the horizontal axis represents the Doppler frequency of the target, and the vertical axis represents the Doppler frequency estimate based on the outputs of the first Doppler demultiplexing unit 212 and the second Doppler demultiplexing unit 212.

[0229] In addition, in FIG. 9, the solid line indicates the center frequency f c Doppler frequency estimate (e.g., f d_VFT (1)), and the dotted line represents the center frequency f c The Doppler frequency estimate (f d_VFT (2)). However, in Figure 9, f c (2)>f c An example of case (1) is shown below.

[0230] In addition, in FIG. 9, the circles indicate the Doppler frequency f d_VFT (1)+n al / T rs 9, the Doppler frequency estimates (values ​​on the vertical axis) indicated by circles represent the Doppler frequency estimates based on the output of the first Doppler demultiplexing unit 212 for the number of Doppler aliasing n al values ​​that do not depend on (e.g., f d_VFT (1)).

[0231] In addition, in FIG. 9, the square marks indicate the Doppler frequency f d_VFT (1)+n al / T rs 9, the Doppler frequency estimates (values ​​on the vertical axis) indicated by squares represent the Doppler frequency estimates based on the output of the second Doppler demultiplexing unit 212 for the number of Doppler aliasing n al A value that depends on (e.g., f est (f d_VFT(1) , n al)) In addition, for example, the interval between the square marks in the vertical axis direction in FIG. 9 is the Doppler frequency resolution Δf d The interval is larger than the Doppler fold count n al , which can be detected as different Doppler frequency estimates depending on the

[0232] The Doppler determination unit 213 calculates, for example, the square plots shown in FIG. 9 as the Doppler frequency estimate f d_VFT Based on (1), f shown in Eq. (17) est (f d_VFT(1) , n al ) may be used for the calculation. Then, the Doppler determination unit 213 may, for example, use the calculated value (the value on the vertical axis of the plot of square marks shown in FIG. 9) and the center frequency f c Doppler frequency estimate f when using the second chirp signal in (2) d_VFT (2) (dotted line in Figure 9) al (For example, the n al ) is the estimated Doppler aliasing number n alest may be set to

[0233] In this way, the Doppler determination unit 213 determines the center frequency f c The Doppler peak observed by the reflected wave signal corresponding to the first chirp signal (1) (for example, the circle in Figure 9, the first peak position) and the center frequency f c (1) and the center frequency f c (2) Ratio f c (2) / f c Based on (1), the center frequency f c (2) The Doppler peak of the reflected wave signal corresponding to the second chirp signal (for example, the square mark in FIG. 9, the second peak position) is estimated, and the number of folds n is determined based on the degree of agreement (closeness) between the estimated Doppler peak and the Doppler peak observed by the reflected wave signal corresponding to the second chirp signal (for example, the dotted line in FIG. 9, the third peak position). alest The degree of match is determined by taking into consideration that the Doppler-peak value changes due to aliasing.

[0234] In addition, f c (2)>f c In (1), f c (2) / f c The larger (1), or f c (2) <f c In (1), f c (2) / f c The smaller (1), the more likely it is that n al f according to est (f d_VFT(1) , n al ) differences (e.g., f d_VFT(1) Since the difference between the Doppler and the Doppler signal is large, the Doppler determination unit 213 determines whether the number of times of aliasing n al Distinguishing Doppler frequencies by (for example, the number of folds n al This makes it easier to determine the

[0235] On the other hand, the number of folds n al The difference in Doppler frequency due to the rs ), the Doppler frequency becomes ambiguous, so the Doppler aliasing number estimate n alest The probability of an error in the estimation of .

[0236] Here, the number of Doppler folds n al When the center frequency f c (2) The Doppler frequency aliasing component n observed using the second chirp signal al ×f c (2) / f c (1) / T rs and the number of times n of foldback of the second Doppler analyzer 210. al The frequency interval is n al / T rs The difference is ±1 / (2T rs ) is expressed by the following equation (18).

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[0237] For example, n al If is positive, the maximum n that satisfies the following equation (19)al Until Δn al is ±1 / (2T rs ), and the Doppler determination unit 213 can estimate aliasing without ambiguity. al "n almax " Also, for example, n al If is negative, n al =-n almax Therefore, the detection range of the Doppler frequency is, for example, n almax is magnified twice as much.

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[0238] For example, n almax If = 2, f c (2)>f c In the case of (1), f c (2) is f c (1), and may be set to a frequency lower than 1.25 times f c (2) <f c In the case of (1), f c (1) is f c (2) may be set to a frequency lower than 1.25 times the frequency of (2). almax If = 3, f c (2)>f c In the case of (1), f c (2) is f c may be set to a frequency lower than (7 / 6) times (1), and f c (2) <f c In the case of (1), f c (1) is f c The frequency may be set lower than (7 / 6) times (2). almax The value of is not limited to 2 or 3, and may be other values.

[0239] For example, f c (1) and f c (2) is n almaxIf the condition for =2 is satisfied, the Doppler frequency f d The detection range of is ±2 / (T rs ), which is twice the Doppler frequency range when using one transmitting antenna.

[0240] In addition, within the passing frequency range of the radar transmitter 100 or the radar receiver 200, f c (1) and f c (2) may be set, and the expansion of the Doppler frequency detection range may be subject to the restrictions of the passing frequency characteristics of the radar transmitter 100 or the radar receiver 200.

[0241] For example, f c (1) and f c In the setting of (2), the maximum Doppler aliasing number n is set based on the maximum Doppler frequency of the assumed target. almax is determined, and the judging condition and f that satisfy Eq. (17) are c (1) and f c (2) may be determined. c (1) and f c (2) is set within the passing frequency range of the radar transmitter 100 or the radar receiver 200. c (1) and f c (2) may be determined.

[0242] An example of the operation of Doppler determination section 213 has been described above.

[0243] In FIG. 2, the direction estimation unit 214 receives information (for example, a distance index f b_cfar (q), and the separation index information (f demul_Tx#1 (q), f demul_Tx#2 (q)~ f demul_Tx#Nt Based on (q)), target direction estimation processing is performed.

[0244] For example, the direction estimation unit 214 calculates a distance index f b_cfar (q) and the separation index information of the Doppler multiplex signal (q) (fdemul_Tx#1 (q), f demul_Tx#2 (q)~ f demul_Tx#Nt (q)), the output of the q-th Doppler analyzer 210 is extracted, and the q-th virtual receiving array correlation vector h q (f b_cfar (q), f demul_Tx#1 (q), f demul_Tx#2 (q)~ f demul_Tx#Nt (q)) is generated and direction estimation processing is performed, where q=1,2.

[0245] qth virtual receiving array correlation vector h q (f b_cfar (q), f demul_Tx#1 (q), f demul_Tx#2 (q)~ f demul_Tx#Nt As shown in equation (20), the virtual receiving array correlation vector h(q) contains Nt×Na elements, which is the product of the number of transmitting antennas Nt and the number of receiving antennas Na. q (f b_cfar (q), f demul_Tx#1 (q), f demul_Tx#2 (q)~ f demul_Tx#Nt (q)) is used for processing to estimate the direction of a reflected wave signal from a target based on the phase difference between the receiving antennas 202. Here, the integer z is 1 to Na. Note that the direction estimation unit 214 performs direction estimation processing using the outputs of the first and second Doppler demultiplexing units 212 with the same distance index, so f b_cfar (1) = f b_cfar (2) = f b_cfar Let's say.

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[0246] In equation (20), h cal[b] is an array correction value that corrects the phase deviation and amplitude deviation between the transmitting array antennas and the receiving array antennas, where b is an integer between 1 and (Nt×Na).

[0247] The direction estimation unit 214 calculates, for example, a direction estimation evaluation function value P H (θ u , fb_cfar , f demul_Tx#1 (1)~f demul_Tx#Nt (1), f demul_Tx#1 (2)~ f demul_Tx#Nt (2)) in the azimuth direction θ u is varied within a predetermined angle range to calculate a spatial profile. The direction estimation unit 214 extracts a predetermined number of maximum peaks from the calculated spatial profile in descending order, and outputs the azimuth direction of the maximum peak as an arrival direction estimate (e.g., positioning output).

[0248] The direction estimation evaluation function value P H (θ u , f b_cfar , f demul_Tx#1 (1)~f demul_Tx#Nt (1), f demul_Tx#1 (2)~ f demul_Tx#Nt There are various methods for (2)) depending on the arrival direction estimation algorithm. For example, the estimation method using an array antenna disclosed in Non-Patent Document 3 may be used.

[0249] For example, if Nt × Na virtual receiving arrays are arranged at equal intervals d H When the antennas are arranged linearly, the beamformer method can be expressed as in the following equation (21). In addition to the beamformer method, methods such as Capon and MUSIC can also be applied. In equation (21), the superscript H is the Hermitian transpose operator.

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[0250] Also, in equation (21), a q (θ u ) is the azimuth direction θ u This shows the direction vector of the virtual receiving array for the arriving wave of λ, and is expressed by equation (22). q is the center frequency f c is the wavelength of the radar transmission signal (e.g., the qth chirp signal) in case (q), and λ q =C0 / f c (q).

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[0251] Also, the azimuth direction θ u is a vector obtained by varying the azimuth range for estimating the direction of arrival at a predetermined azimuth interval β1. For example, θ u is set as follows: θ u =θmin + uβ1, integer u=0~ NU NU=floor[(θmax-θmin) / β1]+1 Here, floor(x) is a function that returns the largest integer value that does not exceed the real number x.

[0252] The direction estimation unit 214 calculates, for example, the direction vector a q (θ u ), as shown in equation (23), the center frequency f c (1) and f c (2) The direction vector a(θ) of the virtual receiving array for the arriving wave in the azimuth direction θ at the mean center frequency u ) may be used in common. a is the center frequency (f c (1)+ f c (2)) / 2, and λ is the wavelength of the radar transmission signal. a =2C0 / (f c (1)+f c In this case, the direction estimator 214 calculates the direction vector a(θ u ) can be used in common for processing each chirp signal, which also has the effect of reducing the memory capacity required to store the direction vectors of the virtual receiving array.

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[0253] In the above example, the direction estimation unit 214 calculates the azimuth direction as the arrival direction estimated value, but the present invention is not limited to this, and the arrival direction can be estimated in the elevation angle direction, or in the azimuth direction and elevation angle direction by using MIMO antennas arranged in a rectangular grid. For example, the direction estimation unit 214 may calculate the azimuth direction and elevation angle direction as the arrival direction estimated value and output them as positioning outputs.

[0254] By the above operation, the direction estimation unit 214 outputs the distance index f b_cfar (q), separation index information of Doppler multiplexed signals (f demul_Tx#1 (q), f demul_Tx#2 (q), ...,f demul_Tx#Nt The direction estimator 214 may output the estimated direction of arrival value at (q) as a positioning output. b_cfar (q), separation index information of Doppler multiplexed signals (f demul_Tx#1 (q), f demul_Tx#2 (q), ...,f demul_Tx#Nt The direction estimation unit 214 may output the positioning output (or the positioning result) to, for example, a vehicle control device in the case of an in-vehicle radar, or to an infrastructure control device in the case of an infrastructure radar, both not shown.

[0255] Further, the direction estimation unit 214 may, for example, use the Doppler frequency information f determined by the Doppler determination unit 213. d_VFT(1) +n alest / T rs , and f c (2) / f c (1)(f d_VFT(1) +n alest / T rs ) or both may be output.

[0256] Also, the distance index f b_cfar may be converted into distance information using equation (1) and output.

[0257] Furthermore, the Doppler frequency information determined by the Doppler determination unit 213 may be converted into relative velocity information and output. c Doppler frequency information f d_VFT(1) +n alest / T rs relative velocity v d To convert it into:

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[0258] Similarly, the center frequency f determined by the Doppler determination unit 213 c (2) Doppler frequency information f c (2) / f c (1)(f d_VFT(1) +n alest / T rs ) relative velocity v d When converted into the above equation, the value becomes the same as equation (24), as in the following equation (25), so the relative velocity component information may be output as a common value (or a unified value) for different center frequencies.

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[0259] As described above, in this embodiment, the radar device 10 alternately switches between, for example, the first center frequency and the second center frequency that satisfy one of the formulas (10) to (15) for each transmission period in which a transmission signal is transmitted from the transmitting antenna 106. This allows the radar device 10 to determine the number of aliasings based on the deviation of the Doppler frequency in Doppler analysis that corresponds to the difference in center frequency. Therefore, the radar device 10 can expand the Doppler frequency range (or the maximum value of the relative velocity) in which Doppler multiplexed signals can be separated, for example, depending on the number of aliasings that can be determined.

[0260] As described above, according to this embodiment, the Doppler frequency range (or the maximum value of the relative velocity) in which no ambiguity occurs can be expanded, and the radar device 10 can thereby detect targets (e.g., arrival directions) with high accuracy in a wider Doppler frequency range.

[0261] Furthermore, in this embodiment, the Doppler frequency range in which Doppler multiplexed signals can be separated is expanded by setting the center frequency of the chirp signal, so it is possible to omit applying a method such as increasing the sampling rate of the A / D converter. Therefore, according to this embodiment, it is possible to suppress the complexity of the hardware configuration of the radar device 10 and also to suppress an increase in the power consumption or heat generation in the radar device 10. Furthermore, in this embodiment, the Doppler frequency range in which Doppler multiplexed signals can be separated is expanded by setting the center frequency of the chirp signal, so it is possible to omit applying a method such as increasing the sampling rate of the A / D converter. r Therefore, according to this embodiment, it is possible to suppress a reduction in the detectable distance range of the radar device 10 or a deterioration in distance resolution.

[0262] In this embodiment, the first chirp signal and the second chirp signal have the same modulation parameters other than the center frequency, but the present disclosure is not limited to this. w It is sufficient if the chirp signals have the same relationship as (q).

[0263] For example, as shown in Figure 10, w (1)=B w (2), T sw (1)≠T sw (2), D m (1)≠D m (2) may be used. In this case, the frequency sweep time T SW Although the frequency sweep bandwidth B wis the same, and the distance resolution ΔR (= C0 / 2B w ) match, the radar device 10 can obtain the same effect by performing the operation according to the embodiment of the present disclosure described above.

[0264] Also, for example, as shown in FIG. sw (1)≠T sw By setting (2), when the beat signal output from each radio receiving unit 203 is discretely sampled in the A / D conversion unit 207 of each signal processing unit 206, a predetermined time range (range gate) T sw (1)≠T sw The number of discrete sampling data obtained in (2) is different. Therefore, the beat frequency analysis unit 208 calculates, for example, the number of discrete sampling data obtained in (2) for the transmission period T r Every predetermined time range (range gate) T sw N obtained by data Instead of performing FFT processing on the discrete sampled data, the following operation may be performed.

[0265] For example, the beat frequency analysis unit 208 may analyze the first chirp signal within a predetermined time range (range gate) T sw N obtained in (1) data (1) discrete sampling data is subjected to FFT processing, and a predetermined time range (range gate) T sw N obtained in (2) data (2) The beat frequency analysis unit 208 may perform FFT processing on the discrete sampling data. data (1) Pieces and N data (2) The smaller of these is N data Subsequent processing may then be performed.

[0266] (Embodiment 2) The radar device according to this embodiment may be similar to the radar device 10 shown in FIG.

[0267] In the first embodiment, the center frequency f of the first chirp signal is c (1) and the center frequency f of the second chirp signalc The conditions under which the number of Doppler aliasing can be determined in relation to (2) have been described. For example, in the first embodiment, the operation of determining the number of Doppler aliasing in Doppler determination unit 213 when the determination conditions are satisfied has been described, and it has been explained that the Doppler frequency range can be expanded to more than twice the Doppler frequency range when one transmitting antenna is used.

[0268] Here, for example, in a MIMO radar using unevenly spaced Doppler multiplexing, if there are multiple reflected waves from approximately the same distance, and if the Doppler intervals of these reflected waves match the Doppler multiplexing interval (or a multiple of the Doppler multiplexing interval), the radar device 10 is more likely to erroneously detect the Doppler frequency range with uneven intervals, which may result in incorrect separation of the Doppler multiplexed signal or a large error in measuring the angle of the multiple reflected waves.

[0269] In this embodiment, a radar device that can improve detection performance even in such a situation, in addition to the effects of the first embodiment, will be described. For example, in this embodiment, when the center frequency f c (1) and the center frequency f of the second chirp signal c The conditions for determining the number of reflected waves in (2) will be explained. For example, the central frequency f of the first chirp signal set in the signal generation control unit 104 of the radar transmitter 100 is c (1) and the center frequency f of the second chirp signal c The setting conditions (determinable conditions) of (2) and the operation of Doppler determination section 213 are different from those of embodiment 1. The following describes this embodiment, focusing on the operations of the parts that are different from embodiment 1.

[0270] [Judgment possible conditions] First, the center frequency f of the first chirp signal set in the signal generation control unit 104 of the radar transmitter 100 is c (1) and the center frequency f of the second chirp signal c The setting conditions (determinable conditions) of (2) will be explained below.

[0271] The Doppler shifter 105 of the radar transmitter 100 performs a phase rotation φ shown in, for example, equation (4). n (m) may be used. In this case, the Doppler multiple interval Δf DDM is expressed by the following equation (26).

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[0272] Doppler multiple interval Δf shown in equation (26) DDM Some of these are not used for Doppler multiplexing and are not assigned transmission signals, so they are unevenly spaced at multiples of the Doppler multiplexing interval. Here, δ is an integer equal to or greater than 1. When δ is 1, the Doppler multiplexing interval Δf DDM is the widest, and as δ increases, the Doppler multiple interval Δf DDM For example, the narrower the Doppler multiplexing interval, the more the mutual interference between Doppler multiplexed signals increases, so it is more preferable to set δ to a smaller integer such as δ=1.

[0273] For example, the Doppler frequency f of the reflected waves from two targets (hereinafter referred to as "Target #1" and "Target #2") detected at the same distance index is d1_T#1 , f d1_T#2 However, the Doppler multiple interval Δf DDM (or multiple N of Doppler multiple interval mul ×Δf DDM ), the Doppler frequency f d1_T#1 , f d1_T#2 is expressed by the following equations (27) and (28), and the Doppler frequency f d1_T#1 , f d1_T#2 has the relationship of Equation (29). Here, the center frequency f c The relational expression when the first chirp signal (1) is used is shown below. f d1_T#1 = f d_T#1_VFT (1)+ n al_T#1 / T rs (27) f d1_T#2 = f d1_T#2_VFT (1)+ n al_T#2 / T rs (28) |f d1_T#1 -f d1_T#2 |= N mul ×Δf DDM (29)

[0274] where f d_T#1_VFT (1) is the estimated Doppler frequency of Target #1 detected by the first Doppler analyzer 210 and the first Doppler demultiplexer 212, and f d1_T#2_VFT (1) is the estimated Doppler frequency of Target #2 detected by the first Doppler analyzer 210 and the first Doppler demultiplexer 212. al_T#1 represents the number of Doppler folds of Target#1, and n al_T#2 represents the number of Doppler aliasing of Target#2. al_T#1 and n al_T#2 takes an integer value.

[0275] Also, N mul is a natural number within the expected Doppler frequency range. For example, N mul is the maximum number of folds n that satisfies equation (19). almax Using N mul ∈{1,…,(Nt+δ)×n almax}, N mul ∈{1,…,(Nt+δ)×n almax} may be set to a value within a narrower range than

[0276] For the relational expression between the two targets (Target #1, Target #2) expressed as above, the radar device 10 calculates the center frequency f c When the Doppler frequency is observed using the second chirp signal (2), the following relations (30), (31), and (32) are obtained. Note that the relations (30), (31), and (32) are based on the center frequency f c Doppler frequency f when using the second chirp signal (2) d2_T#1 , f d2_T#2 is the Doppler frequency f d1_T#1 , f d1_T#2 , the center frequency ratio f c (2) / f cThis takes advantage of the fact that it can be calculated by multiplying (1). f d2_T#s1 = f c (2) / f c (1)×(f d_T#1_VFT (1)+ n al_T#1 / T rs ) (30) f d2_T#2 = f c (2) / f c (1)×(f d1_T#2_VFT (1)+ n al_T#2 / T rs ) (31) |f d2_T#1 -f d2_T#2 |= f c (2) / f c (1) × (N mul ×Δf DDM ) (32)

[0277] where f c (2) / f c (1) × (N mul ×Δf DDM ) and the Doppler multiplex interval, N mul ×Δf DDM (for example, the difference between the value of equation (32) and the value of equation (29)) is the Doppler frequency resolution Δf d The center frequency ratio f c (2) / f c (1) may be set.

[0278] For example, the radar device 10 determines the center frequency f of the first chirp signal so as to satisfy the "second determination condition (1)" of the following equation (33): c (1) and the center frequency f of the second chirp signal c (2) may be determined.

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[0279] This allows, for example, the center frequency f cWhen the outputs of the second Doppler analysis unit 210 and the second Doppler demultiplexing unit 212 using the second chirp signal (2) are used, the Doppler frequencies of Target #1 and Target #2 are calculated by subtracting the Doppler frequency estimates (for example, Doppler multiplex interval Δf DDM (or Δf DDM From the interval (a multiple of ) of the Doppler frequency resolution Δf d It is observed as a Doppler frequency shifted from the

[0280] Therefore, the radar device 10 can suppress overlapping of Doppler multiplexed signal components between two reflected waves observed at the same distance, for example, and improve the performance of separating the Doppler multiplexed signals of the two reflected waves. For example, the second determination condition (1) is that the Doppler frequency estimates of Target #1 and Target #2 detected by the first Doppler analysis unit 210 and the first Doppler multiplex separation unit 212 are within the Doppler multiplex interval Δf DDM (or Δf DDM Even if Doppler demultiplexing is difficult for Target#1 and Target#2, Doppler demultiplexing can be performed for Target#1 and Target#2 based on the outputs of the second Doppler analysis unit 210 and the second Doppler demultiplexing unit 212 using the second chirp signal, and Doppler frequency estimates for Target#1 and Target#2 can be obtained.

[0281] where f c (2)> f c In the case of (1), f in the second decidable condition (1) c (1) and f c Condition (2) is expressed by the following equation (34).

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[0282] For example, N mul If =1 is satisfied, then Nmul >1, the second determinable condition (1) may be expressed as the following equation (35).

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[0283] Similarly, f c (2)< f c In the case of (1), f in the second decidable condition (1) c (1) and f c Condition (2) is expressed by the following equation (36).

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[0284] For example, N mul If =1 is satisfied, then N mul >1, the second determinable condition (1) may be expressed as the following equation (37).

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[0285] Similarly, the Doppler frequency f of the reflected waves from two targets (e.g., Target #1 and Target #2) detected at the same distance index is d2_T#1 , f d2_T#2 However, the Doppler multiple interval Δf DDM (or multiple N of Doppler multiple interval mul ×Δf DDM ), the Doppler frequency f d2_T#1 , f d2_T#2 is expressed by the following equations (38) and (39), and the Doppler frequency f d2_T#1 , f d2_T#2 has the relationship of Equation (40). Here, the center frequency f c The relational expression when the second chirp signal (2) is used is shown below. f d2_T#1 = f d_T#1_VFT (2)+ n al_T#1 / T rs (38) f d2_T#2 = f d1_T#2_VFT (2)+ n al_T#2 / T rs (39) |f d2_T#1 -f d2_T#2 |=N mul ×Δf DDM (40)

[0286] where f d_T#1_VFT (2) is the estimated Doppler frequency of Target #1 detected by the second Doppler analyzer 210 and the second Doppler demultiplexer 212, and f d1_T#2_VFT (2) is the estimated Doppler frequency of Target #2 detected by the second Doppler analyzer 210 and the second Doppler demultiplexer 212. al_T#1 represents the number of Doppler folds of Target#1, and n al_T#2 represents the number of Doppler aliasing of Target#2. al_T#1 and n al_T#2 takes an integer value.

[0287] For the relational expression between the two targets (Target #1, Target #2) expressed as above, the radar device 10 calculates the center frequency f c When the Doppler frequency is observed using the first chirp signal (1), the following relations (41), (42), and (43) are obtained. Note that the relations (41), (42), and (43) are based on the center frequency f c Doppler frequency f when using the first chirp signal in (1) d1_T#1 , f d1_T#2 is the Doppler frequency f d2_T#1 , f d2_T#2 , the center frequency ratio f c (1) / f c This takes advantage of the fact that it can be calculated by multiplying (2). f d1_T#1 = fc(1) / fc(2)×(f d_T#1_VFT (2)+ n al_T#1 / T rs ) (41) f d1_T#2 = fc(1) / fc(2)×( fd1_T#2_VFT (2)+ n al_T#2 / T rs ) (42) |f d1_T#1 -f d1_T#2 |= fc(1) / fc(2)×(N mul ×Δf DDM ) (43)

[0288] where f c (1) / f c (2) × (N mul ×Δf DDM ) and the Doppler multiplex interval, N mul ×Δf DDM (for example, the difference between the value of equation (43) and the value of equation (40)) is the Doppler frequency resolution Δf d The center frequency ratio f c (1) / f c (2) may be set.

[0289] For example, the radar device 10 determines the center frequency f of the first chirp signal so as to satisfy the "second determination condition (2)" of the following equation (44): c (1) and the center frequency f of the second chirp signal c (2) may be determined.

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[0290] This allows, for example, the center frequency f c When the outputs of the first Doppler analysis unit 210 and the first Doppler demultiplexing unit 212 using the first chirp signal (1) are used, the Doppler frequencies of Target #1 and Target #2 are calculated based on the Doppler frequency estimates (for example, Doppler multiplex interval Δf DDM (or Δf DDM (intervals of multiples of ) at least the Doppler frequency resolution Δf dIt is observed as a Doppler frequency shifted from the

[0291] Therefore, the radar device 10 can suppress overlapping of Doppler multiplexed signal components between two reflected waves observed at the same distance, for example, and improve the performance of separating the Doppler multiplexed signals of the two reflected waves. For example, the second determination condition (2) is that the Doppler frequency estimates of Target #1 and Target #2 detected by the second Doppler analysis unit 210 and the second Doppler multiplex separation unit 212 are within the Doppler multiplex interval Δf DDM (or Δf DDM Even if Doppler demultiplexing is difficult for Target#1 and Target#2, Doppler demultiplexing can be performed for Target#1 and Target#2 based on the outputs of the first Doppler analysis unit 210 and the first Doppler demultiplexing unit 212 using the first chirp signal, and Doppler frequency estimates for Target#1 and Target#2 can be obtained.

[0292] where f c (2)> f c In the case of (1), f in the second decidable condition (2) c (1) and f c Condition (2) is expressed by the following equation (45).

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[0293] For example, N mul =1 (N mul >1 also holds), the second determinable condition (2) may be expressed as the following formula (46):

number

[0294] Furthermore, if the second determinable condition (2) is satisfied as in the following equation (47), the second determinable condition (1) is also satisfied.

number

[0295] Therefore, for example, the following equation (48) can be expressed as f c (2)>f c This is called the "second determinable condition" for case (1).

number

[0296] Similarly, f c (2) <f c In the case of (1), f in the second decidable condition (2) c (1) and f c Condition (2) is expressed by the following equation (49).

number

[0297] For example, N mul =1 (N mul >1 also holds), the second determinable condition (2) may be expressed as the following formula (50):

number

[0298] Furthermore, for example, from equations (37) and (50), if the second determinable condition (2) is satisfied as in the following equation (51), the second determinable condition (1) is also satisfied.

number

[0299] Therefore, for example, the following equation (52) can be expressed as f c (2) <f c This is called the "second determinable condition" for case (1).

number

[0300] In addition, for example, in the second determination condition shown in Equation (33) or Equation (44), the Doppler frequency resolution Δf d The center frequency f is greater than an integer multiple (for example, α times) of c (1) and f c The condition (2) may be used (where α≧1). In this case, the larger α is, the easier it is for the radar device 10 to perform Doppler separation even when there is noise influence, such as when the received signal level is low. c (2)>f c The second decidable condition shown in equation (48) in the case of (1), and f c (2) <f c The second determinable conditions shown in equation (52) in case (1) may be expressed as the following equations (53) and (54).

number

number

[0301] As an example, f c (1) = 78 GHz, f c (2)>f c (1) Then, for α=1, Nc=128, Nt=3, and δ=1, c (2) is set to be larger than 80.51 GHz, and f c (2) = 83.2 GHz. For example, when α = 1, Nc = 256, Nt = 3, and δ = 1, c (2) = 79.23 GHz, and f c (2) is set to be greater than 80.51GHz.

[0302] The second condition for determining whether the difference between the center frequencies of the chirp signals is |f c (2)-f c (1)| is the expansion condition. For example, if the second determinable condition is satisfied, then the first determinable condition is also satisfied.

[0303] In addition, within the passing frequency range of the radar transmitter 100 or the radar receiver 200, f c (1) and f c (2) may be set, and the expansion of the Doppler frequency detection range may be subject to the restrictions of the passing frequency characteristics of the radar transmitter 100 or the radar receiver 200.

[0304] Furthermore, the second determinable condition may also be set in consideration of the frequency condition constraints shown in equation 18 or 19. This makes it possible to obtain the same effects as in the first embodiment.

[0305] In addition, in the second decidable condition, f c (1) and f c (2) The difference in Doppler frequency observed between and is the Doppler multiple interval Δf DDM For example, a frequency condition may be added to satisfy the conditions shown in the following equations (55) and (56). c (1) and f c (2) may be set.

number

number

[0306] where N mul is a natural number within the range of the expected Doppler frequency. For example, N mul is the maximum number of folds n that satisfies equation (19). almax Using N mul ∈{1,…,(Nt+δ)×n almax}, N mul ∈{1,…,(Nt+δ)×n almax} may be set to a value within a narrower range than

[0307] The determinable conditions have been described above.

[0308] [Doppler detection method] Next, the Doppler determination unit 213 determines the center frequency f that satisfies the second determination condition described above. c (1) and f c (2) may be used to perform the following operations:

[0309] The Doppler determination unit 213 determines, for example, the distance index f b_cfar In the case where the number of pieces of separation index information of the Doppler multiplexed signals output from the first Doppler multiplexing separation unit 212 and the number of pieces of separation index information of the Doppler multiplexed signals output from the second Doppler multiplexing separation unit 212 are the same, the same operation as in embodiment 1 may be performed. This provides the same effect as in embodiment 1.

[0310] On the other hand, the Doppler determination unit 213 determines, for example, the distance index f b_cfar In the case where the number of pieces of separation index information for the Doppler multiplexed signals output from the first Doppler multiplex separation unit 212 is not the same as the number of pieces of separation index information for the Doppler multiplexed signals output from the second Doppler multiplex separation unit 212, the Doppler determination unit 213 may perform the following process. For example, the Doppler determination unit 213 may perform the following process when there are multiple reflected waves from approximately the same distance to the radar device 10, and there is a possibility that multiple reflected waves will be separated in one of the Doppler analysis of the first chirp signal and the Doppler analysis of the second chirp signal, but will not be separated in the other.

[0311] <Case 1> In case 1, for example, the distance index f b_cfar In the following, a case will be described in which a plurality of pieces of separation index information are included for the Doppler multiplexed signals output from the first Doppler multiplexed separation unit 212, and no separation index information is included for the Doppler multiplexed signals output from the second Doppler multiplexed separation unit 212. For example, case 1 is a case in which the Doppler multiplexed signals are separated in the first Doppler multiplexed separation unit 212, but not in the second Doppler multiplexed separation unit 212, such as the following case.

[0312] When there are two reflected waves from approximately the same distance to the radar device 10, it is expected that the separation index information of the Doppler multiplexed signal output from the first Doppler multiplex separation unit 212 and the separation index information of the Doppler multiplexed signal output from the second Doppler multiplex separation unit 212 will each contain the separation index information of the Doppler multiplexed signal for the two reflected waves.

[0313] However, by transmitting using the second chirp signal, for example, as shown in FIG. 1(c), the reflected wave #1 and the reflected wave #2 are separated by a Doppler multiplexing interval Δf DDM , or if it matches a multiple of the Doppler multiplexing interval, some Doppler multiplexed signals may be received as overlapping Doppler frequency components between reflected wave #1 and reflected wave #2. This makes it difficult to separate the Doppler multiplexed signals, and the Doppler multiplexed signals output from the second Doppler multiplexing separation unit 212 may not contain separation index information.

[0314] On the other hand, even if such a reflected wave exists, the radar device 10 satisfies the second determination condition by transmitting using the first chirp signal, so that some Doppler multiplexed signals are not received as overlapping Doppler frequency components in reflected wave #1 and reflected wave #2. This results in a case where separation index information is included in the Doppler multiplexed signal output from the first Doppler multiplex separation unit 212. In such a case, the following operation is performed.

[0315] As an example, the following describes a case where the separation index information of the Doppler multiplexed signal output from the first Doppler multiplex separation unit 212 includes separation index information of the Doppler multiplexed signals of reflected waves from two targets (e.g., Target #1 and Target #2).

[0316] The Doppler determination unit 213 determines, for example, the center frequency f c When using the chirp signal (2), the Doppler frequency f of the reflected waves from the two targets (Target #1 and Target #2) is d2_T#1 , f d2_T#2However, the Doppler multiple interval Δf DDM (or multiple N of Doppler multiple interval mul ×Δf DDM In this case, the Doppler determination unit 213 may perform the following Doppler determination process when the arriving waves overlap.

[0317] For example, the Doppler determination unit 213 determines the Doppler aliasing number n of Target #1 that minimizes the following equation (57). al_#T1 , and the number of Doppler folds of Target #2 n al_#T2 may be calculated.

number

[0318] Here, the number of Doppler folds n al_#T1 and n al_#T2 is an integer value and may be calculated within a range of integer values ​​that covers the Doppler frequency range of the expected target. For example, n al_#T1 and n al_#T2 is the maximum number of folds n that satisfies equation (19). almax Using ±n almax The Doppler fold count n al_#T1 and n al_#T2 When varying, the number of Doppler aliasing times that minimizes equation (57) is n alest_#T1 and n alest_#T2 Also, mod[x,y] is a function that represents the remainder when x is divided by y.

[0319] For example, the center frequency f c When using the chirp signal (2), the Doppler frequency f of the reflected waves from the two targets (Target #1 and Target #2) is d2_T#1 and f d2_T#2 However, the Doppler multiple interval Δf DDM (or multiple N of Doppler multiple interval mul ×Δf DDM) is satisfied. The Doppler determination unit 213 utilizes this fact to determine the number of Doppler aliasing times n alest_#T1 and n alest_#T2 Estimate.

[0320] In equation (57), for example, the number of Doppler aliasing n al_#T1 , n al_#T2 Doppler frequency f d2_T#1 , f d2_T#2 Each of the f est (f d_T#1_VFT(1) , n al_T#1 ) and f est (f d_T#2_VFT(1) , n al_T#2 ), where f est (f d_VFT(1) , n al ) can be a function shown in equation (17). Also, the Doppler frequency estimate f d_T#1_VFT(1) and f d_T#2_VFT(1) are, for example, the distance index f output from the first Doppler demultiplexing unit 212. b_cfar Based on the separation index information of the Doppler multiplex signal in rs ) ≦f d_TargetDoppler <1 / (2T rs ) is the Doppler frequency estimate.

[0321] <Case 2> In case 2, for example, the distance index f b_cfar In the following, a case will be described in which a plurality of pieces of separation index information are included for the Doppler multiplexed signals output from the second Doppler multiplexed separation unit 212, and no separation index information is included for the Doppler multiplexed signals output from the first Doppler multiplexed separation unit 212. For example, case 2 is a case in which the Doppler multiplexed signals are not separated in the first Doppler multiplexed separation unit 212, but are separated in the second Doppler multiplexed separation unit 212, such as the following case.

[0322] When there are two reflected waves from approximately the same distance to the radar device 10, it is expected that the separation index information of the Doppler multiplexed signal output from the first Doppler multiplex separation unit 212 and the separation index information of the Doppler multiplexed signal output from the second Doppler multiplex separation unit 212 will each contain the separation index information of the Doppler multiplexed signal for the two reflected waves.

[0323] However, by transmitting using the first chirp signal, for example, as shown in FIG. 1(c), the reflected wave #1 and the reflected wave #2 are separated by a Doppler multiplexing interval Δf DDM , or if it coincides with a multiple of the Doppler multiplex interval, some Doppler multiplexed signals may be received as overlapping Doppler frequency components between reflected wave #1 and reflected wave #2.

[0324] This makes it difficult to separate the Doppler multiplexed signals, and the Doppler multiplexed signals output from first Doppler multiplex separation section 212 may not contain separation index information.

[0325] On the other hand, even if such a reflected wave exists, the radar device 10 satisfies the second determination condition by transmitting using the second chirp signal, so that some Doppler multiplexed signals are not received as overlapping Doppler frequency components in reflected wave #1 and reflected wave #2. This results in a case where separation index information is included in the Doppler multiplexed signal output from the second Doppler multiplex separation unit 212. In such a case, the following operation is performed.

[0326] As an example, the following describes a case where the separation index information of the Doppler multiplexed signal output from the second Doppler multiplex separation unit 212 includes separation index information of the Doppler multiplexed signals of reflected waves from two targets (e.g., Target #1 and Target #2).

[0327] The Doppler determination unit 213 determines, for example, the center frequency f cWhen using the chirp signal (1), the Doppler frequency f of the reflected waves from two targets (Target #1 and Target #2) is d1_T#1 , f d1_T#2 However, the Doppler multiple interval Δf DDM (or multiple N of Doppler multiple interval mul ×Δf DDM In this case, the Doppler determination unit 213 may perform the following Doppler determination process when the arriving waves overlap.

[0328] For example, the Doppler determination unit 213 determines the Doppler aliasing number n of Target #1 and Target #2 that minimizes the following equation (58). al_#T1 and n al_#T2 may be calculated.

number

[0329] Here, the number of Doppler folds n al_#T1 and n al_#T2 is an integer value and may be calculated within a range of integer values ​​that covers the Doppler frequency range of the expected target. For example, n al_#T1 and n al_#T2 is the maximum number of folds n that satisfies equation (19). almax Using ±n almax The Doppler fold count n al_#T1 and n al_#T2 When varying, the number of Doppler aliasing times that minimizes equation (58) is n alest_#T1 and n alest_#T2 It is written as follows.

[0330] For example, the center frequency f c When using the chirp signal (1), the Doppler frequency f of the reflected waves from two targets (Target #1 and Target #2) is d1_T#1 and f d1_T#2 However, the Doppler multiple interval Δf DDM (or multiple N of Doppler multiple interval mul ×Δf DDM) is satisfied. The Doppler determination unit 213 utilizes this fact to determine the number of Doppler aliasing times n alest_#T1 and n alest_#T2 Estimate.

[0331] In equation (58), for example, the number of Doppler aliasing n al_#T1 , n al_#T2 Doppler frequency f d1_T#1 , f d1_T#2 Each of f est2 (f d_T#1_VFT(2) , n al_T#1 ) and f est2 (f d_T#2_VFT(2) , n al_T#2 ) and the Doppler frequency estimate f d_T#1_VFT(2) and f d_T#2_VFT(2) are the distance index f output from the second Doppler demultiplexing unit 212. b_cfar Based on the separation index information of the Doppler multiplex signal in rs ) ≦f d_TargetDoppler <1 / (2T rs ) is the Doppler frequency estimate.

[0332] Also, f est2 (f d_VFT(2) , n al ) is a function shown in the following equation (59), and is a Doppler frequency estimation value f calculated based on the separation index information of the Doppler multiplexed signal output from the second Doppler multiplex separation unit 212. d_VFT(2) If the number of Doppler folds is n al Doppler frequency (f d_T#1_VFT(2) +n al / T rs ) and calculate the center frequency f c To convert the observed Doppler frequency using the first chirp signal in (1), f c (1) / f c Represents a function that outputs the value multiplied by (2).

number

[0333] By the above-described operation of the Doppler determination unit 213, the distance index f b_cfar In the case where the number of pieces of separation index information of the Doppler multiplexed signals output from the first Doppler multiplex separation unit 212 and the number of pieces of separation index information of the Doppler multiplexed signals output from the second Doppler multiplex separation unit 212 are not the same, the Doppler determination unit 213 determines whether the Doppler frequency of the reflected wave when using a chirp signal of the other center frequency is equal to or greater than the Doppler multiplex interval Δf DDM (or multiple N of Doppler multiple interval mul ×Δf DDM ) and the number of Doppler aliasing can be estimated.

[0334] For example, the Doppler determination unit 213 estimates the Doppler peaks of each of the multiple targets in the other Doppler analysis in which the multiple reflected wave signals are not separated, based on the results of one of the Doppler analyses, for example, the Doppler analysis corresponding to the first chirp signal and the Doppler analysis corresponding to the second chirp signal, in which the multiple reflected wave signals are separated, and determines the number of times the Doppler frequency of each of the multiple targets folds over, based on the intervals between the estimated Doppler peaks between the multiple targets and the Doppler multiplexing interval.

[0335] In this embodiment, the subsequent processing of the radar device 10 may be the same as in embodiment 1. In addition, the radar device 10 may, for example, alest_#T1 and n alest_#T2 As described above, in this embodiment, the radar device 10 may output the Doppler frequency estimate as a positioning output using the center frequency f of the first chirp signal that satisfies the second determination condition. c (1) and the center frequency f of the second chirp signal c By using (2), the effect of the first embodiment can be obtained.

[0336] Furthermore, in the radar device 10, for example, the Doppler frequencies of the reflected waves from two targets are Doppler multiplexing intervals Δf DDM (or multiple N of Doppler multiple interval mul ×Δf DDM ), and it may be difficult to perform Doppler demultiplexing of the targets using one of the chirp signals. Even in this case, the radar device 10 determines that the Doppler frequencies of the reflected waves from the two targets are equal to the Doppler multiplexing interval Δf for the other chirp signal. DDM (or multiple N of Doppler multiple interval mul ×Δf DDM ), and by making it different from the Doppler resolution of the Doppler analysis unit 210 at least, it is possible to perform Doppler demultiplexing of the two targets.

[0337] As a result, in this embodiment, the radar device 10 can improve the detection performance of multiple waves arriving from the same distance, thereby improving the target detection probability in the radar device 10 and reducing the non-detection probability, thereby improving radar detection performance.

[0338] (Modification of the second embodiment) As a modification of the second embodiment, the Doppler frequency f d_TargetDoppler is -1 / (2T rs ) ≦f d_TargetDoppler <1 / (2T rs ), the radar device 10 determines whether the center frequency f of the first chirp signal satisfies the second determination condition. c (1) and the center frequency f of the second chirp signal c (2) may be used to perform processing that omits the process of estimating the number of aliasing waves in the Doppler determination unit 213. For example, the radar device 10 may perform processing to separate and detect a plurality of reflected waves without estimating the number of aliasing waves.

[0339] In this case, the Doppler determination unit 213 may perform the following processing of Case 1a and Case 2a, instead of the processing of Case 1 and Case 2 described above.

[0340] <Case 1a> In case 1a, for example, the distance index f b_cfar In this case, the Doppler multiplexed signal output from the first Doppler multiplexed separation unit 212 includes multiple separation index information, and the Doppler multiplexed signal output from the second Doppler multiplexed separation unit 212 does not include separation index information, for example, in the following cases.

[0341] When there are two reflected waves from approximately the same distance to the radar device 10, it is expected that the separation index information of the Doppler multiplexed signal output from the first Doppler multiplex separation unit 212 and the separation index information of the Doppler multiplexed signal output from the second Doppler multiplex separation unit 212 will each contain the separation index information of the Doppler multiplexed signal for the two reflected waves.

[0342] However, by transmitting using the second chirp signal, for example, as shown in FIG. 1(c), the reflected wave #1 and the reflected wave #2 are separated by a Doppler multiplexing interval Δf DDM , or if it coincides with a multiple of the Doppler multiplex interval, some Doppler multiplexed signals may be received as overlapping Doppler frequency components between reflected wave #1 and reflected wave #2.

[0343] This makes it difficult to separate the Doppler multiplexed signals, resulting in the case where separation index information is not included in the Doppler multiplexed signals output from the second Doppler multiplex separation unit 212. On the other hand, even when such reflected waves exist, the radar device 10 satisfies the second determination condition by transmitting using the first chirp signal, so that some Doppler multiplexed signals are not received as overlapping Doppler frequency components in reflected wave #1 and reflected wave #2.

[0344] Therefore, the Doppler multiplexed signal output from the first Doppler multiplexing separation unit 212 includes separation index information (assuming a case in which reflected waves #1 and #2 arrive similar to case 1). In this case, the following description will explain the operations that differ from case 1.

[0345] As an example, the following describes a case where the separation index information of the Doppler multiplexed signal output from the first Doppler multiplex separation unit 212 includes separation index information of the Doppler multiplexed signals of reflected waves from two targets (e.g., Target #1 and Target #2).

[0346] The Doppler determination unit 213 determines, for example, the center frequency f c When using the chirp signal (2), the Doppler frequency f of the reflected waves from the two targets (Target #1 and Target #2) is d2_T#1 , f d2_T#2 However, the Doppler multiple interval Δf DDM (or multiple N of Doppler multiple interval mul ×Δf DDM ) In this case, the Doppler determination unit 213 may output separation index information of the Doppler multiplexed signal output from the first Doppler multiplex separation unit 212 to the direction estimation unit 214, for example.

[0347] The direction estimation unit 214 estimates the distance index f b_cfar and the separated index information of the Doppler multiplexed signal (q=1). The direction estimator 214 may perform the direction estimation process using q=1 in equation (21), for example.

[0348] <Case 2a> In case 2a, for example, the distance index f b_cfarIn this case, the Doppler multiplexed signal output from the second Doppler multiplexed separation unit 212 includes multiple separation index information, and the Doppler multiplexed signal output from the first Doppler multiplexed separation unit 212 does not include separation index information, for example, in the following cases.

[0349] When there are two reflected waves from approximately the same distance to the radar device 10, it is expected that the separation index information of the Doppler multiplexed signal output from the first Doppler multiplex separation unit 212 and the separation index information of the Doppler multiplexed signal output from the second Doppler multiplex separation unit 212 will each contain the separation index information of the Doppler multiplexed signal for the two reflected waves.

[0350] However, when the first chirp signal is transmitted, for example, as shown in FIG. 1(c), the reflected wave #1 and the reflected wave #2 are separated by a Doppler multiplexing interval Δf DDM , or if it coincides with a multiple of the Doppler multiplex interval, some Doppler multiplexed signals may be received as overlapping Doppler frequency components between reflected wave #1 and reflected wave #2.

[0351] This makes it difficult to separate the Doppler multiplexed signals, and the Doppler multiplexed signals output from first Doppler multiplex separation section 212 may not contain separation index information.

[0352] On the other hand, even when such a reflected wave exists, the radar device 10 satisfies the second determination condition by transmitting using the second chirp signal, and therefore some Doppler multiplexed signals are not received as overlapping Doppler frequency components in reflected wave #1 and reflected wave #2. This results in a case where separation index information is included in the Doppler multiplexed signal output from the second Doppler multiplex separation unit 212 (assuming a case where reflected waves #1 and #2 arrive similar to case 2). In this case, the following description will explain the operation that differs from case 2.

[0353] As an example, the following describes a case where the separation index information of the Doppler multiplexed signal output from the second Doppler multiplex separation unit 212 includes separation index information of the Doppler multiplexed signals of reflected waves from two targets (e.g., Target #1 and Target #2).

[0354] The Doppler determination unit 213 determines, for example, the center frequency f c When using the chirp signal (1), the Doppler frequency f of the reflected waves from two targets (Target #1 and Target #2) is d1_T#1 , f d1_T#2 However, the Doppler multiple interval Δf DDM (or multiple N of Doppler multiple interval mul ×Δf DDM ) In this case, the Doppler determination unit 213 may output separation index information of the Doppler multiplexed signal output from the second Doppler multiplex separation unit 212 to the direction estimation unit 214, for example.

[0355] The direction estimation unit 214 estimates the distance index f b_cfar and the separation index information of the Doppler multiplexed signal (q=2). The direction estimator 214 may perform the direction estimation process using q=2 in equation (21), for example.

[0356] Case 1a and Case 2a have been described above.

[0357] In this way, the Doppler frequency f d_TargetDoppler is -1 / (2T rs ) ≦f d_TargetDoppler <1 / (2T rs ) in the Doppler frequency range, the center frequency f of the first chirp signal that satisfies the second determination condition c (1) and the center frequency f of the second chirp signal c By using (2), the following effects can be obtained.

[0358] For example, if the Doppler frequencies of the reflected waves from two targets are equal to the Doppler multiple interval Δf DDM (or multiple N of Doppler multiple interval mul ×Δf DDM ) and it may be difficult to perform Doppler demultiplexing of the target based on one of the chirp signals. Even in this case, the Doppler frequency interval of the reflected waves from the two targets can be increased by using the other chirp signal (a chirp signal with a different center frequency) to the Doppler frequency interval Δf DDM (or multiple N of Doppler multiple interval mul ×Δf DDM ), and can be set to an interval greater than the Doppler resolution of the Doppler analysis unit 210. Thus, the radar device 10 can perform Doppler demultiplexing of two targets.

[0359] In this way, in a variation of the second embodiment, the radar device 10 may perform direction estimation processing based on the results of one of the Doppler analyses of the first chirp signal and the second chirp signal, in which multiple reflected wave signals are separated.

[0360] As a result, for example, even if, in the Doppler analysis of the reflected wave signal corresponding to one chirp signal, the interval between the Doppler frequencies (Doppler peaks) corresponding to multiple reflected waves at approximately the same distance from the radar device 10 matches the Doppler multiplex interval (or a multiple of the Doppler multiplex interval), the radar device 10 can separate and detect the Doppler multiplex signals corresponding to each of the multiple reflected waves based on the results of the Doppler analysis of the reflected wave signal corresponding to the other chirp signal.

[0361] As a result, in the modification of the second embodiment, the radar device 10 can improve the detection performance of a plurality of reflected waves arriving from the same distance, thereby improving the probability of detecting a target and reducing the probability of non-detection in the radar device 10. Therefore, according to the modification of the second embodiment, the radar detection performance of the radar device 10 can be improved.

[0362] (Embodiment 3) In the first embodiment, an example of the configuration of the radar device including one radar transmission signal generator has been shown, but the configuration of the radar device is not limited to this, and a radar device including multiple radar transmission signal generators may also be used.

[0363] 11 shows an example of a configuration in which the radar transmitter 100a of the radar device 10a includes two radar transmission signal generators 101. In the first embodiment, the radar device 10 includes one radar transmission signal generator 101, and generates radar transmission waves (e.g., chirp signals) with different center frequencies at a transmission period T r In contrast to this, in this embodiment, as shown in FIG. 11, a radar device 10a including a plurality of radar transmission signal generators 101 transmits radar transmission waves (for example, chirp signals) of different center frequencies at a transmission period T r Each signal is transmitted simultaneously from a plurality of transmitting antennas 106. As in the first embodiment, this configuration also has the effect of widening the detectable Doppler frequency range.

[0364] The following describes the operation of this embodiment, focusing mainly on examples of operation that differ from the first embodiment.

[0365] [Configuration example of radar transmitter 100a] 11 shows, as an example, a configuration in which the radar transmitter 100a of the radar device 10a includes two radar transmission signal generators 101. Hereinafter, the two radar transmission signal generators 101 are referred to as the "first radar transmission signal generator 101 (or radar transmission signal generator 101-1)" and the "second radar transmission signal generator 101-2 (or radar transmission signal generator 101-2)."

[0366] 11, the configuration of each radar transmission signal generator 101 may be the same as that of Embodiment 1. Each radar transmission signal generator 101 generates a radar transmission signal under the control of, for example, a signal generation controller 104.

[0367] The signal generation control unit 104 controls the generation of radar transmission signals by the first and second radar transmission signal generation units 101 (e.g., the modulation signal generation unit 102 and the VCO 103). For example, the signal generation control unit 104 may set parameters (e.g., modulation parameters) related to the chirp signals so that the first and second radar transmission signal generation units 101 transmit chirp signals with different center frequencies. Hereinafter, the chirp signal generated in the first radar transmission signal generation unit 101 will be referred to as the "first chirp signal," and the chirp signal generated in the second radar transmission signal generation unit 101 will be referred to as the "second chirp signal."

[0368] As in the first embodiment, the modulation parameters for the chirp signal include, for example, the center frequency f c (q), frequency sweep bandwidth B w (q), sweep start frequency f cstart (q), sweep end frequency f cend (q), frequency sweep time T sw (q) and frequency sweep rate of change D m (q) may be included. m (q)=B w (q) / T sw (q). Also, B w (q)= f cend (q)-f cstart (q) and f c (q)=(f cstart (q)+f cend (q) / 2. For example, q=1, 2 may represent the modulation parameters of the first chirp signal when q=1, and may represent the modulation parameters of the second chirp signal when q=2.

[0369] As in the first embodiment, the signal generation control unit 104 selects, for example, a center frequency f c In the following, as an example, among the modulation parameters set for the first chirp signal and the second chirp signal, the center frequency f cThe following describes a case where (q) is different from each other and other modulation parameters other than the center frequency are the same (or common). However, this is not limited to this. For application of an embodiment of the present disclosure, for example, it is sufficient that the resolution of the distance axis in the first chirp signal and the second chirp signal is the same. Therefore, the frequency sweep bandwidth B w It is sufficient to set chirp signals such that (q) has the same relationship.

[0370] Furthermore, the signal generation control unit 104 may, for example, determine the center frequency f c The modulation signal generating section 102 and the VCO 103 may be controlled so that two different chirp signals (q) are simultaneously transmitted (or output) Nc times each.

[0371] 12 shows an example of chirp signals (e.g., first chirp signal and second chirp signal) output by the first and second radar transmission signal generators 101 under the control of the signal generation controller 104. Note that while FIG. 12 shows an example of an up-chirp waveform in which the modulation frequency gradually increases over time, the present invention is not limited to this, and a down-chirp waveform in which the modulation frequency gradually decreases over time may also be used. Similar effects can be obtained regardless of whether the modulation frequency is an up-chirp or a down-chirp.

[0372] In FIG. 12, the first chirp signal and the second chirp signal each have a transmission period T r In the following, unless otherwise specified, the frequency sweep bandwidth, frequency sweep time (also called range gate), and frequency sweep rate represent parameters with the same values ​​for the first chirp signal and the second chirp signal, respectively, and B w (1)=B w (2)=B w , T sw (1)=T sw (2)=T sw , D m (1)=D m (2)=D m It can be expressed as:

[0373] Furthermore, the frequency sweep bandwidths of the chirp signals with different center frequencies may not include overlapping bands, as shown in Figure 12(a), or may include overlapping bands, as shown in Figure 12(b). In one embodiment of the present disclosure, similar effects can be achieved regardless of whether the frequency sweep bandwidths include overlapping bands, as long as the relationship between the center frequencies of the first chirp signal and the second chirp signal satisfies a predetermined condition.

[0374] In one embodiment of the present disclosure, the transmission period T r may be set to, for example, several hundred μs or less, and the transmission time interval of the radar transmission signal may be set to a relatively short time. As a result, even if the center frequencies of the first chirp signal and the second chirp signal are different, the frequency of the beat signal of the received reflected wave (e.g., beat frequency index) does not change, and the radar device 10a can detect this as a change in Doppler frequency.

[0375] The first chirp signal output from the first radar transmission signal generation unit 101 (e.g., VCO 103) is input to, for example, N1 Doppler shift units 105 (represented as Doppler shift units 105-1 to 105-N1, for example) among the Nt Doppler shift units 105. The first chirp signal output from the first radar transmission signal generation unit 101 is input to, for example, N3 mixer units 204 (e.g., mixer units 204 of antenna system processing units 201-1 to 201-N3) among the Na mixer units 204 of the radar reception unit 200a.

[0376] On the other hand, the second chirp signal output from the second radar transmission signal generation unit 101 (e.g., VCO 103) is input to, for example, N2 Doppler shift units 105 (e.g., Doppler shift units 105-N1+1 to 105-Nt) out of the Nt Doppler shift units 105. Also, the second chirp signal output from the second radar transmission signal generation unit 101 is input to, for example, N4 mixer units 204 (e.g., antenna system processing units 201-N3+1 to 201-Na) out of the Na mixer units 204 in the radar reception unit 200a.

[0377] Here, N1 + N2 = Nt, and N3 + N4 = Na. Note that N1 and N2 are each 2 or more, and Nt may be 4 or more. Furthermore, N3 and N4 are each 1 or more, and Na may be 2 or more.

[0378] The output signals of the N1 Doppler shift units 105 to which the first chirp signal is input are amplified to a predetermined transmission power and radiated into space from each transmitting antenna 106 (for example, Tx#1 to Tx#N1). The output signals of the N2 Doppler shift units 105 to which the second chirp signal is input are amplified to a predetermined transmission power and radiated into space from each transmitting antenna 106 (for example, Tx#N1+1 to Tx#Nt). As a result, the first chirp signal and the second chirp signal are respectively amplified to a predetermined transmission power and radiated into space from each transmitting antenna 106 (for example, Tx#N1+1 to Tx#Nt). r are transmitted simultaneously.

[0379] Hereinafter, the N1 Doppler shift units 105 (e.g., Doppler shift units 105-1 to 105-N1) to which the first chirp signal is input and the respective transmit antennas 106 (e.g., Tx#1 to Tx#N1) that transmit the output signals of these N1 Doppler shift units 105 are referred to as a "first transmit sub-block." Also, the N2 Doppler shift units 105 (e.g., Doppler shift units 105-N1+1 to 105-Nt) to which the second chirp signal is input and the respective transmit antennas 106 (e.g., Tx#N1+1 to Tx#Nt) that transmit the output signals of these N2 Doppler shift units 105 are referred to as a "second transmit sub-block."

[0380] For example, the Doppler shift unit 105 included in the first transmission sub-block shifts the first chirp signal by a transmission period T r Doppler shift amount DOP nsub1 To give the phase rotation φ nsub1 and outputs the Doppler-shifted signal to the transmitting antennas 106 (for example, Tx#1 to Tx#N1). Here, nsub1 is an integer between 1 and N1. Furthermore, the Doppler shifter 105 included in the second transmitting sub-block applies a transmission period T rDoppler shift amount DOP nsub2 To give the phase rotation φ nsub2 and outputs the Doppler-shifted signal to a transmitting antenna 106 (for example, Tx#N1+1 to Tx#Nt), where nsub2 is an integer between 1 and N2.

[0381] The Doppler shift amount DOP in the Doppler shift unit 105 included in the first and second transmission sub-blocks is nsub1 (or phase rotation φ nsub1 ), and the Doppler shift DOP nsub2 (or phase rotation φ nsub2 An example of a method for adding the .) will be described later.

[0382] Furthermore, when Nt is an even number, the number of transmit antennas 106 included in the first and second transmission sub-blocks may be made the same by setting N1 = N2, for example. When Nt is an odd number, the number of transmit antennas 106 included in the first and second transmission sub-blocks may be made approximately the same, with a difference of one transmit antenna, by setting N1 = (Nt + 1) / 2 or N1 = (Nt - 1) / 2, for example. In this way, the number of transmit antennas 106 included in the first sub-block (e.g., transmit antennas 106 transmitting the first chirp signal) and the number of transmit antennas 106 included in the second transmission sub-block (e.g., transmit antennas 106 transmitting the second chirp signal) may be set to be the same or different by one. By setting the number of transmitting antennas 106 included in the first and second sub-blocks to be equal or approximately equal, the radar device 10a can obtain the effect of further increasing (for example, approximately doubling) the Doppler multiplexing interval when performing Doppler multiplexing using the first chirp signal and the second chirp signal, compared to the first embodiment.

[0383] In the first embodiment, the first chirp signal and the second chirp signal are switched in a time division manner (for example, the first chirp signal and the second chirp signal are switched in a transmission period T r Therefore, the Doppler frequency range is ±1 / 2T. rsDoppler multiplexed signals are multiplexed in rs >T r On the other hand, in this embodiment, as shown in FIG. 12, the first chirp signal and the second chirp signal are transmitted with a transmission period T r Since the signals are transmitted simultaneously, the Doppler frequency range is ±1 / 2T. r For example, in the first embodiment, T rs =2T r In comparison with the case where Doppler multiplexing is performed using the first chirp signal and the second chirp signal, this embodiment enables multiplexing and transmission of Doppler multiplexed signals over twice the Doppler frequency range. Therefore, by making the number of transmitting antennas 106 included in the first and second transmitting sub-blocks the same or approximately the same, the Doppler multiplexing interval when Doppler multiplexing using the first chirp signal and the second chirp signal can be expanded by approximately four times compared to the first embodiment.

[0384] For example, if the Doppler multiplex interval during Doppler multiplex transmission is close, in the case of a target with a spread in Doppler components, interference between the Doppler multiplexed signals is likely to occur, degrading the direction estimation accuracy and target detection accuracy. In this embodiment, the Doppler multiplex interval during Doppler multiplexing can be extended, thereby reducing the occurrence of such interference between Doppler multiplexed signals and suppressing degradation of the direction estimation accuracy and target detection accuracy.

[0385] Furthermore, in this embodiment, since the Doppler multiplexing interval during Doppler multiplexing can be extended, even if more transmitting antennas 106 are used for Doppler multiplexing, it is possible to reduce the occurrence of interference between Doppler multiplexed signals and suppress deterioration in direction estimation accuracy and target detection accuracy. Therefore, in this embodiment, more transmitting antennas 106 can be used for Doppler multiplexing compared to embodiment 1. In this way, when Doppler multiplexing is performed using more transmitting antennas 106, this embodiment is more preferable than embodiment 1.

[0386] [Configuration example of radar receiver 200a] 11, the radar receiver 200a includes, for example, Na receiving antennas 202 (for example, Rx#1 to Rx#Na) to form an array antenna. The radar receiver 200a also includes, for example, Na antenna system processors 201-1 to 201-Na, a CFAR unit 211, a Doppler demultiplexing unit 212, a Doppler determination unit 213, and a direction estimation unit 214.

[0387] Each receiving antenna 202 receives a reflected wave signal, which is a radar transmission signal (e.g., a first chirp signal and a second chirp signal) reflected from a target, and outputs the received reflected wave signal to the corresponding antenna system processing unit 201 as a received signal.

[0388] Each antenna system processing unit 201 includes a receiving radio unit 203 and a signal processing unit 206 .

[0389] The radio reception unit 203 has a mixer unit 204 and an LPF 205. In the radio reception unit 203, the mixer unit 204 mixes the received reflected wave signal (received signal) with a chirp signal, which is a transmission signal.

[0390] Here, the first chirp signal output from the first radar transmission signal generation unit 101-1 (e.g., VCO 103) is input to the mixer units 204 of, for example, N3 antenna system processing units 201 (e.g., antenna system processing units 201-1 to 201-N3) among the Na antenna system processing units 201. In the antenna system processing units 201-1 to 201-N3, the outputs of the mixer units 204 are passed through the LPFs 205, so that the output of the mixer units 204 corresponding to the reflected wave of the second chirp signal has a high frequency outside the passband of the LPFs 205. Therefore, the LPFs 205 tend to output a beat signal having a frequency corresponding to the delay time of the reflected wave signal of the first chirp signal.

[0391] Similarly, the second chirp signal output from the second radar transmission signal generation unit 101-2 (e.g., VCO 103) is input to the mixer units 204 of, for example, N4 antenna system processing units 201 (e.g., antenna system processing units 201-N3+1 to 201-Na) among the Na antenna system processing units 201. In the antenna system processing units 201-N3+1 to 201-Na, the outputs of the mixer units 204 are passed through the LPFs 205, so that the output of the mixer units 204 corresponding to the reflected wave of the first chirp signal has a high frequency outside the passband of the LPFs. As a result, the LPFs 205 tend to output a beat signal having a frequency corresponding to the delay time of the reflected wave signal of the second chirp signal.

[0392] Therefore, antenna system processing units 201-1 to 201-N3 process the reflected wave signals of the first chirp signals received by receiving antennas 202-1 to 202-N3. Hereinafter, antenna system processing unit 201 (e.g., reception radio unit 203 and signal processing unit 206) that processes the reflected wave of the first chirp signal, and receiving antenna 202 connected to antenna system processing unit 201 that processes the reflected wave of the first chirp signal will be referred to as the "first receiving sub-block."

[0393] Furthermore, antenna system processing units 201-N3+1 to 201-Na process the reflected wave signals of the second chirp signals received by receiving antennas 202-N3+1 to 202-Na. Hereinafter, antenna system processing unit 201 (e.g., reception radio unit 203 and signal processing unit 206) that processes the reflected wave of the second chirp signal, and receiving antenna 202 connected to antenna system processing unit 201 that processes the reflected wave of the second chirp signal will be referred to as the "second receiving sub-block."

[0394] Here, N3+N4=Na. Note that N3 and N4 may each be 1 or greater, and Na may be 2 or greater.

[0395] Each antenna system processing unit 201-z included in the q-th receiving sub-block qThe signal processing unit 206 includes an A / D conversion unit 207, a beat frequency analysis unit 208, and a Doppler analysis unit 210. When q=1, z1=1 to N3, and when q=2, z2=N3+1 to Na.

[0396] The signal output from the LPF 205 (for example, a beat signal) is converted into discrete sample data by the A / D converter 207 in the signal processor 206, which is discretely sampled.

[0397] The beat frequency analysis unit 208 included in the q-th reception sub-block analyzes N data The discrete sample data are subjected to FFT processing. Here, the range gate is set to the frequency sweep time T sw Set (q). For example, q=1,2. When q=1, T sw (1) represents the frequency sweep time of the first chirp signal, and when q=2, T sw (2) represents the frequency sweep time of the second chirp signal. As a result, the signal processing unit 206 outputs a frequency spectrum in which a peak appears at the beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave). During FFT processing, the beat frequency analysis unit 208 may multiply the signal by a window function coefficient such as a Han window or a Hamming window. Using the window function coefficient makes it possible to suppress side lobes that occur around the beat frequency peak.

[0398] Here, the z-th chirp pulse of the q-th receiving sub-block obtained by transmitting the m-th chirp pulse of the q-th chirp signal is q The beat frequency response output from the beat frequency analysis unit 208 in the th signal processing unit 206 is referred to as "RFT zq (f b , m) where f b represents the beat frequency index, which corresponds to the FFT index (bin number). For example, f b =0,~,N data / 2-1, z1=1~N3, z2=N3+1~Na, m=1,~,NC where q=1 or 2. The beat frequency index f b The smaller the beat frequency, the shorter the delay time of the reflected wave signal (for example, the closer the distance to the target).

[0399] The zth subblock of the qth received subblock q The Doppler analyzer 210 in the qth signal processor 206 analyzes the N C Beat frequency response RFT obtained by transmitting a single chirp pulse zq (f b , 1), RFT zq (f b , 2), ~, RFT zq (f b , N C ) to find the distance index f b For example, the Doppler analysis unit 210 of the q-th receiving sub-block may estimate the Doppler frequency from the reflected wave signal of the q-th chirp signal reflected by the target.

[0400] For example, N c If is a power of 2, FFT processing can be applied in Doppler analysis. In this case, the FFT size is N c The maximum Doppler frequency at which aliasing does not occur, derived from the sampling theorem, is ±1 / (2T r ) and the Doppler frequency index f s The Doppler frequency interval is 1 / (N c ×T r ) and the Doppler frequency index f s The range of f s = -N c / 2, ~, 0, ~, N c / 2-1.

[0401] In the following, as an example, c The case where N is a power of 2 will be explained. cIf is not a power of 2, for example, by including zero-padded data, FFT processing can be performed with a data size that is a power of 2. Furthermore, the Doppler analysis unit 210 may multiply by a window function coefficient such as a Han window or a Hamming window during FFT processing. Applying a window function can suppress side lobes that occur around the beat frequency peak.

[0402] For example, the zth subblock of the qth received subblock q The output VFT of the Doppler analysis unit 210 in the signal processing unit 206 zq (f b , f s ) is shown in the following equation (60). Note that j is the imaginary unit, z1=1 to N3, z2=N3+1 to Na, and q=1, 2.

number

[0403] The processing in each component of the signal processing unit 206 has been described above.

[0404] The CFAR unit 211 may include, for example, a first CFAR unit 211 (or CFAR unit 211-1) and a second CFAR unit 211 (or CFAR unit 211-2) corresponding to the first chirp signal and the second chirp signal having different center frequencies, respectively. Similarly, the Doppler demultiplexing unit 212 may include, for example, a first Doppler demultiplexing unit 212 (or Doppler demultiplexing unit 212-1) and a second Doppler demultiplexing unit 212 (or Doppler demultiplexing unit 212-2) corresponding to the first chirp signal and the second chirp signal having different center frequencies, respectively.

[0405] 11 shows a configuration in which CFAR units 211 are provided in parallel (CFAR units 211-1 and 211-2), but it is also possible to provide a single CFAR unit 211 and have its inputs switched over sequentially for processing. Also, while Fig. 11 shows a configuration in which Doppler demultiplexing units 212 are provided in parallel (Doppler demultiplexing units 212-1 and 212-2), it is also possible to provide a single Doppler demultiplexing unit 212 and have its inputs switched over sequentially for processing.

[0406] In FIG. 11, the CFAR unit 211 performs CFAR processing (for example, adaptive threshold determination) using the output from the Doppler analysis unit 210 of the signal processing unit 206 included in the q-th receiving sub-block, and calculates the distance index f b_cfar and the Doppler frequency index f s_cfar Extract.

[0407] As shown in FIG. 11, the CFAR unit 211 may include a first CFAR unit 211 (also referred to as CFAR unit 211-1) that performs CFAR processing using the output of the Doppler analysis unit 210 of the signal processing unit 206 included in the first receiving sub-block, and a second CFAR unit 211 (also referred to as CFAR unit 211-2) that performs CFAR processing using the output of the Doppler analysis unit 210 of the signal processing unit 206 included in the second receiving sub-block.

[0408] The q-th CFAR unit 211 (q=1, 2) adds the power of the output of the Doppler analysis unit 210 of the signal processing unit 206 included in the q-th receiving sub-block, and performs two-dimensional CFAR processing consisting of a distance axis and a Doppler frequency axis (corresponding to relative velocity), or CFAR processing that combines one-dimensional CFAR processing, as shown in the following equation (61). As for the two-dimensional CFAR processing or the CFAR processing that combines one-dimensional CFAR processing, for example, the processing disclosed in Non-Patent Document 2 may be applied. Here, z1 = 1 to N3, and z2 = N3 + 1 to Na.

number

[0409] The qCFAR unit 211 adaptively sets a threshold value and calculates the distance index f th at which the received power is greater than the threshold value. b_cfar (q), the Doppler frequency index f s_cfar (q), and received power information PowerFT(f b_cfar (q), f s_cfar (q)) is output to the q-th Doppler demultiplexing unit 212.

[0410] The Doppler demultiplexing unit 212 may include a first Doppler demultiplexing unit 212 (or may be referred to as a Doppler demultiplexing unit 212-1) that performs Doppler demultiplexing processing using the outputs of the Doppler analysis unit 210 and the first CFAR unit 211 of the signal processing unit 206 included in the first receiving sub-block, and a second Doppler demultiplexing unit 212 (or may be referred to as a Doppler demultiplexing unit 212-2) that performs Doppler demultiplexing processing using the outputs of the Doppler analysis unit 210-2 and the second CFAR unit 211 of the signal processing unit 206 included in the second receiving sub-block.

[0411] The q-th Doppler demultiplexing unit 212 (q=1, 2) receives information (for example, a distance index f b_cfar (q), the Doppler frequency index f s_cfar (q), and received power information PowerFT(f b_cfar (q), f s_cfar Based on (q)), the output from the Doppler analysis unit 210 included in the qth receiving sub-block is used to separate the transmission signals (e.g., reflected wave signals for the transmission signals) transmitted from each transmitting antenna 106 from the Doppler multiplexed transmitted signal (hereinafter referred to as "Doppler multiplexed signal").

[0412] The q-th Doppler demultiplexing unit 212 outputs, for example, information about the separated signals to the Doppler determining unit 213 and the direction estimating unit 214. The information about the separated signals includes, for example, a distance index f b_cfarThe separation index information of the first Doppler demultiplexing unit 212 is a Doppler frequency index obtained by separating the signals transmitted from the transmitting antennas Tx#1, Tx#2, to Tx#N1 included in the first transmission sub-block, and each of the indexes (f demul_Tx#1 , f demul_Tx#2 , ~, f demul_Tx#N1 ) Similarly, the separation index information of the second Doppler demultiplexing unit 212 is a Doppler frequency index obtained by separating the signals transmitted from the transmitting antennas Tx#N1+1, Tx#N1+2, to Tx#Nt included in the second transmission sub-block, and is represented by (f demul_Tx#N1+1 , f demul_Tx#N1+2 , ~, f demul_Tx#Nt ) is written as

[0413] The q-th Doppler demultiplexing unit 212 outputs the output from the q-th Doppler analysis unit 210 to the direction estimation unit 214. The q-th Doppler demultiplexing unit 212 uses information input from the q-th CFAR unit 211 (for example, the distance index f b_cfar (q), the Doppler frequency index f s_cfar (q), and received power information PowerFT(f b_cfar (q), f s_cfar Based on (q)), the output from the Doppler analyzer 210 included in the q-th reception sub-block may be output to the direction estimator 214.

[0414] The operation of the q-th Doppler demultiplexing unit 212 will be described below together with the operation of the Doppler shift unit 105 in the radar transmitter 100a.

[0415] [How to set the Doppler shift amount] The Doppler shift units 105-1 to 105-N1 included in the first transmission sub-block shift the first chirp signal by a period T r Doppler shift amount DOP nsub1 To give the phase rotation φ nsub1and outputs the Doppler-shifted signal to the transmitting antenna 106 (for example, Tx#1 to Tx#N1). Here, nsub1=1 to N1. In this embodiment, the Doppler shift amount DOP nsub1 The intervals (Doppler shift intervals) may not be set to equal intervals, but may be set to unequal intervals such that at least one Doppler interval is different.

[0416] For example, the nsub1-th Doppler shift unit 105 generates different Doppler shift amounts DOP for the m-th input first chirp signal. nsub1 The phase rotation φ nsub1 (m) is assigned to the signals and output. As a result, different Doppler shift amounts are assigned to the transmission signals transmitted from the plurality of transmission antennas 106. For example, in this embodiment, when the Doppler multiplexing number N DM =N1, where m=1~N C where nsub1 is an integer between 1 and N1.

[0417] Similarly, the Doppler shift units 105-N1+1 to 105-Nt included in the second transmission sub-block shift the second chirp signal by a period T r Doppler shift amount DOP nsub2 To give the phase rotation φ nsub2 and outputs the Doppler-shifted signal to the transmitting antenna 106 (for example, Tx#N1+1 to Tx#Nt). Here, nsub2=1 to N2. In this embodiment, the Doppler shift amount DOP is calculated between the Doppler shifters 105-N1+1 to 105-Nt (or between the transmitting antennas 106-N1+1 to 106-Nt). nsub2 The intervals (Doppler shift intervals) may not be set to equal intervals, but may be set to unequal intervals such that at least one Doppler interval is different.

[0418] In this way, by setting the Doppler shift amount in the Doppler shifter 105 of the first and second transmission sub-blocks, the first Doppler demultiplexer 212, which will be described later, can separate the Doppler indexes of Tx#1 to Tx#N1 by the same operation as the Doppler demultiplexer 212 in the first embodiment, and can obtain ±1 / T r Furthermore, the second Doppler demultiplexing unit 212 described later operates in the same manner as the Doppler demultiplexing unit 212 in the first embodiment to separate the Doppler indexes Tx#N1+1 to Tx#Nt, and calculates the Doppler frequency in the range of ±1 / T r Based on the output of the Doppler demultiplexing unit 212, the Doppler determining unit 213 described later can determine whether or not the Doppler frequency is folded back based on the difference in the Doppler frequency by performing the same operation as the Doppler determining unit 213 in the first embodiment, and can calculate the Doppler frequency within the range of ±1 / T r It is possible to calculate Doppler frequencies beyond the range of

[0419] The operation of the Doppler shift units 105-1 to 105-N1 included in the first transmission sub-block can be explained by substituting "Nt" with "N1" in the description of the operation between the Doppler shift units 105-1 to 105-Nt (or between the transmission antennas 106-1 to 106-Nt) in the first embodiment. rs " to "T r " is the same as the operation in which " is replaced with ", so a detailed explanation of the operation will be omitted.

[0420] Furthermore, the operation of the Doppler shift units 105-N1+1 to 105-Nt included in the second transmission sub-block can be explained by substituting "Nt" with "N2" in the description of the operation between the Doppler shift units 105-N1+1 to 105-Nt (or between the transmission antennas 106-N1+1 to 106-Nt) in the first embodiment. rs " to "T r " is the same as the operation in which " is replaced with ", so a detailed explanation of the operation will be omitted.

[0421] For example, in the present embodiment, for the equation (5) explained in the first embodiment, the Doppler shift units 105-1 to 105-N1 of the first transmission sub-block calculate different Doppler shift amounts DOP nsub1 The phase rotation φ as shown in the following equation (62) nsub1 (m) is assigned.

number

[0422] Similarly, the Doppler shift units 105-N1+1 to 105-Nt of the second transmission sub-block perform a Doppler shift DOP that differs from one another among the Doppler shift units 105 for the m-th input second chirp signal. nsub2 The phase rotation φ as shown in the following equation (63) nsub2 (m) is assigned.

number

[0423] Here, A is a coefficient that gives the positive or negative polarity of 1 or -1. Also, δ1 and δ2 are integers equal to or greater than 1. Note that round(N C / (N1+δ1)) and round(N C The term (2π / N in equation (62)) is introduced for the purpose of making the phase rotation amount an integer multiple of the Doppler frequency interval in the Doppler analysis unit 210. However, the present invention is not limited to this. C )×round(N C Similarly, instead of the term (2π / N C )×round(N C Instead of the term 2π / (N2+δ2), 2π / (N2+δ2) may be used.

[0424] Also, φ 01 , φ 02 are the initial phases, which may be equal or different. For example, φ 01and φ 02 The Doppler frequency will be the same whether or not Δφ is equal. 01 , Δφ 02 are reference Doppler shift phases, which may be equal or different. For example, Δφ 01 and Δφ 02 Whether they are equal or different, the Doppler frequencies will match.

[0425] For example, the radar device 10a performs unequal Doppler multiplexing on the first chirp signal and the second chirp signal with Doppler multiplexing numbers N1 and N2, respectively.

[0426] In the following, (2π / N C )×round(N C / (N1+δ1)) or 2π / (N1+δ1) is assigned to the first chirp signal as the Doppler multiplexing interval "ΔDOP min1 Similarly, (2π / N C )×round(N C / (N2+δ2)) or 2π / (N2+δ2) is assigned to the second chirp signal. min2 " is called.

[0427] As an example of the case where the number of transmitting antennas is Nt=4, in equation (62), N1=2, Δφ 01 =0, φ 01 =0, A=1, δ1=1, N C is a multiple of 3, and the phase rotation φ nsub1 (m)=2π(nsub1-1)×(m-1) / 3 is the transmission period T r Since the first chirp signal is added every 100 m, the Doppler shift is DOP1 = φ1(m) / {2π(m-1)T r}=0, DOP2=φ2(m) / {2π(m-1)T r}=1 / (3T r ) The top rows of (a) to (d) in FIG. 13 show examples of arrangement of Doppler multiplexed signals when transmitting the first chirp signal.

[0428] As an example of the case where the number of transmitting antennas is Nt=4, in equation (63), Nt=4, N2=2, Δφ 02 =0, φ 02 =0, A=1, δ2=1, N C is a multiple of 3, and the phase rotation φ nsub2 (m)=2π(nsub2-1)×(m-1) / 3 is the transmission period T r Since the second chirp signal is added every 100 ms, the Doppler shift is DOP1=0, DOP2=1 / (3T r The bottom rows of (a) to (d) in FIG. 13 show examples of arrangement of Doppler multiplexed signals when transmitting second chirp signals.

[0429] The arrangement of the Doppler-multiplexed signals for the first chirp signal and the second chirp signal shown in (a) of Fig. 13 is the same. This arrangement makes it easy for the Doppler determination unit 213 (described later) to calculate the Doppler frequency shift in the Doppler-multiplexed signal multiplexed onto the first chirp signal and the second chirp signal when the first chirp signal and the second chirp signal are received.

[0430] The arrangement of the Doppler multiplexed signals is not limited to the example shown in Figure 13(a), and the arrangement of the Doppler multiplexed signals for the first chirp signal and the second chirp signal may be different, for example, as shown in Figure 13(b), Figure 13(c), and Figure 13(d).

[0431] For example, in FIG. 13(b), Δφ 02 By setting ≠0, the Doppler multiplexed signal for the second chirp signal may be arranged with an offset by a predetermined Doppler frequency from the arrangement of the Doppler multiplexed signal for the first chirp signal.

[0432] Also, for example, in (c) of FIG. 13, the first chirp signal and the second chirp signal are each subjected to ±1 / T rThe Doppler range of the signal is divided into 3 (=(N2+δ2)), and two Doppler multiplexed signals are assigned to the divided range. In (c) of FIG. 13, nsub1=1, 2 in equation (62) may be used for the Doppler multiplexed signals for the first chirp signal, and nsub2=2, 3 in equation (63) may be used for the Doppler multiplexed signals for the second chirp signal. For example, the allocation of Doppler multiplexed signals within the (N1+δ1) (=(N2+δ2)) division may be made different for the Doppler multiplexed signals between the first chirp signal and the second chirp signal.

[0433] Also, for example, in (d) of Figure 13, by setting δ2 = 2 in equation (63), a different allocation from the Doppler multiplexing interval of the Doppler multiplexing signal for the first chirp signal (for example, ΔDOPmin1 ≠ ΔDOPmin2) may be applied to the Doppler multiplexing signal for the second chirp signal.

[0434] As an example of the case where the number of transmitting antennas is Nt=5, in equation (62), N1=2, Δφ 01 =0, φ 01 =0, A=1, δ1=2, N C is a multiple of 4, and the phase rotation φ nsub1 (m)=π(nsub1-1)×(m-1) / 2 is the transmission period T r Since the first chirp signal is added every 100 m, the Doppler shift is DOP1 = φ1(m) / {2π(m-1)T r}=0, DOP2=φ2(m) / {2π(m-1)T r}=1 / (4T r ) The top rows of (a) to (d) in FIG. 14 show examples of arrangement of Doppler multiplexed signals when transmitting the first chirp signal.

[0435] As an example of the case where the number of transmitting antennas is Nt=5, in equation (63), Nt=5, N2=3, Δφ 02 =0, φ 02 =0, A=1, δ2=1, N C is a multiple of 4, and the phase rotation φ nsub2 (m)=π×(m-1) / 2 is the transmission period T rSince the second chirp signal is added every 100 ms, the Doppler shift is DOP1=0, DOP2=1 / (4T r The bottom rows of (a) to (d) in FIG. 14 show examples of arrangement of Doppler multiplexed signals when transmitting second chirp signals.

[0436] The arrangement of the Doppler-multiplexed signals for the first chirp signal and the second chirp signal shown in (a) of Fig. 14 is the same. This arrangement makes it easy for the Doppler determination unit 213 (described later) to calculate the Doppler frequency shift in the Doppler-multiplexed signal multiplexed onto the first chirp signal and the second chirp signal when the first chirp signal and the second chirp signal are received.

[0437] The arrangement of the Doppler multiplexed signals is not limited to the example of FIG. 14(a), and the arrangement of the Doppler multiplexed signals for the first chirp signal and the second chirp signal may be different, for example, as shown in FIG. 14(b), FIG. 14(c), and FIG. 14(d).

[0438] For example, in FIG. 14(b), Δφ 02 By setting ≠0, the Doppler multiplexed signal for the second chirp signal may be arranged with an offset by a predetermined Doppler frequency from the arrangement of the Doppler multiplexed signal for the first chirp signal.

[0439] Also, for example, in (c) of FIG. 14, the first chirp signal and the second chirp signal are each subjected to ±1 / T r The Doppler range of is divided into 4 (=(N2+δ2)), and two or three Doppler multiplexed signals are assigned. In (c) of FIG. 14, nsub1=1, 2 in equation (62) may be set for the Doppler multiplexed signals for the first chirp signal, and nsub2=3, 4, 5 in equation (63) may be set for the Doppler multiplexed signals for the second chirp signal. For example, the allocation of Doppler multiplexed signals within the (N1+δ1) (=(N2+δ2)) division may be made different for the Doppler multiplexed signals between the first chirp signal and the second chirp signal.

[0440] Also, for example, in (d) of Figure 14, by setting δ1 = 1 in equation (62), a different allocation from the Doppler multiplexing interval of the Doppler multiplexing signal for the first chirp signal (for example, ΔDOPmin1 ≠ ΔDOPmin2) may be applied to the Doppler multiplexing signal for the second chirp signal.

[0441] [Example of operation of Doppler demultiplexing unit 212] The first Doppler demultiplexing unit 212 detects the Doppler shift amount DOP between the Doppler shift units 105-1 to 105-N1 (for example, between the transmission antennas 106-1 to 106-N1) included in the first transmission sub-block. nsub1 The Doppler shift intervals are not equal, but at least one of the Doppler intervals is set to be different, and the transmitted signals are separated and received.

[0442] The first Doppler demultiplexing unit 212 separates the signals that have been Doppler multiplexed at irregular intervals in the same manner as in the first embodiment, based on the outputs of the Doppler analysis unit 210 and the CFAR unit 211 in the first reception sub-block. Then, the first Doppler demultiplexing unit 212 separates the signals that have been Doppler multiplexed at irregular intervals in the same manner as in the first embodiment, based on the distance index f b_cfar (1), the distance index f b_cfar Separation index information (f demul_Tx#1 , f demul_Tx#2 ,~, f demul_Tx#N1 ), and outputs the output of the Doppler analysis unit 210 to the Doppler determination unit 213.

[0443] Note that the operation of the Doppler shift units 105-1 to 105-N1 included in the first transmission sub-block can be expressed as T by replacing Nt with N1 in the description of the operation between the Doppler shift units 105-1 to 105-Nt (for example, between the transmission antennas 106-1 to 106-Nt) in the first embodiment. rs T r In response to this, the operation of the first Doppler demultiplexing unit 212 is the same as that in the description of the operation of the Doppler shifter 105 in the first embodiment, with "Nt" replaced with "N1" and "Trs " to "T r " can be used to separate signals Doppler multiplexed between transmitting antennas 106-1 to 106-N1. Therefore, detailed description of the operation of first Doppler demultiplexing section 212 will be omitted.

[0444] Furthermore, the second Doppler demultiplexing unit 212 detects the Doppler shift amount DOP between the Doppler shift units 105-N1+1 to 105-Nt (for example, between the transmission antennas 106-N1+1 to 106-Nt) included in the second transmission sub-block. nsub2 The Doppler shift intervals are not equal, but at least one of the Doppler intervals is set to be different, and the transmitted signals are separated and received.

[0445] The second Doppler demultiplexing unit 212 separates the signals Doppler multiplexed at irregular intervals in the same manner as in the first embodiment, based on the outputs of the Doppler analysis unit 210 and the CFAR unit 211 in the second reception sub-block. Then, the second Doppler demultiplexing unit 212 separates the signals Doppler multiplexed at irregular intervals in the same manner as in the first embodiment, based on the distance index f b_cfar (2), the distance index f b_cfar Separation index information (f demul_Tx#N1+1 , f demul_Tx#N1+2 ,~, f demul_Tx#Nt(=N1+N2) ), and outputs the output of the Doppler analysis unit 210 to the Doppler determination unit 213.

[0446] Note that the operation of the Doppler shift units 105-N1+1 to 105-Nt included in the second transmission sub-block can be expressed as follows: in the description of the operation between the Doppler shift units 105-1 to 105-Nt (for example, between the transmission antennas 106-1 to 106-Nt) in the first embodiment, Nt is replaced with N2, and T rs T r In response to this, the operation of the second Doppler demultiplexing unit 212 is the same as that in the description of the operation of the Doppler shifter 105 in the first embodiment, with "Nt" replaced with "N2" and "T rs " to "T r", the signals Doppler multiplexed among the transmitting antennas 106-N1+1 to 106-Nt can be demultiplexed. Therefore, a detailed description of the operation of the second Doppler demultiplexing section 212 will be omitted.

[0447] [Example of operation of Doppler determination unit 213] 11, the Doppler determination unit 213 determines the Doppler frequency corresponding to the Doppler peak based on the outputs of the first Doppler demultiplexing unit 212 and the second Doppler demultiplexing unit 212. For example, the Doppler determination unit 213 determines the Doppler frequency f d_TargetDoppler is the Doppler frequency range -1 / (2T r ) ≦ f d_TargetDoppler <1 / (2T r ), the Doppler detection range can be further expanded by determining the Doppler frequency of the target.

[0448] For example, the Doppler determination unit 213 determines the distance index f b_cfar (1) and f b_cfar (2) is common to the separation index information (f demul_Tx#1 , f demul_Tx#2 ,~,f demul_Tx#N1 ) and separation index information (f demul_Tx#N1+1 , f demul_Tx#N1+2 ,~,f demul_Tx#Nt ) to the Doppler frequency range -1 / (2T r ) ≦ f d_TargetDoppler <1 / (2T r ) and determine the Doppler frequency of the target including the Doppler frequency exceeding the Doppler frequency of the target.

[0449] The Doppler frequency range in the Doppler determination unit 213 is −1 / (2T r ) ≦ f d_TargetDoppler <1 / (2T r), the principle of determining the Doppler frequency of a target including a Doppler frequency exceeding 1 / 2 Hz is, as in the first embodiment, based on the fact that the center frequencies of the first chirp signal and the second chirp signal, which are radar transmission signals generated by the signal generation control unit 104 and the radar transmission signal generation unit 101, are different from each other.

[0450] In the first embodiment, the Doppler frequency is determined based on the change in Doppler frequency in the Doppler multiplexed signal for the same transmitting antenna 106. In contrast, in this embodiment, the Doppler determination unit 213 determines the Doppler frequency based on the change in Doppler frequency in the Doppler multiplexed signal for a different transmitting antenna 106. When a different transmitting antenna 106 is used, the reception phase changes, but the received Doppler frequency does not change. For this reason, as in the first embodiment, the Doppler determination unit 213 determines the Doppler frequency range -1 / (2T r ) ≦ f d_TargetDoppler <1 / (2T r ) can be used to determine the Doppler frequency of targets containing Doppler frequencies exceeding 100 kHz.

[0451] The operating principle of the Doppler frequency determination process and an example of the operation of Doppler determination unit 213 differ from the operating principle of the Doppler frequency determination process and an example of the operation of Doppler determination unit 213 described in embodiment 1 in the following points (1), (2), and (3). (1) "T rs " to "T r " and replace it with (2) In the first embodiment, the Doppler determination unit 213 determines the distance index f output from the first Doppler demultiplexing unit 212. b_cfar Separation index information (f demul_Tx#1 (1), f demul_Tx#2 (1), ~,f demul_Tx#Nt Based on (1), the Doppler frequency of the target is within the Doppler frequency range -1 / (2T rs ) ≦f d_TargetDoppler <1 / (2T rs ) and the estimated Doppler frequency f d_VFTIn contrast to this, in this embodiment, the Doppler determination unit 213 calculates the distance index f b_cfar Separation index information (f demul_Tx#1 , f demul_Tx#2 , ~,f demul_Tx#N1 ), the Doppler frequency of the target is in the Doppler frequency range -1 / (2T r ) ≦f d_TargetDoppler <1 / (2T r ) and the estimated Doppler frequency f d_VFT (1) is calculated, and (3) In the first embodiment, the Doppler determination unit 213 determines the distance index f output from the second Doppler demultiplexing unit 212. b_cfar (2) Separation index information of Doppler multiplexed signals (f demul_Tx#1 (2), f demul_Tx#2 (2), ~,f demul_Tx#Nt (2)), the Doppler frequency of the target is within the Doppler frequency range -1 / (2T rs ) ≦f d_TargetDoppler <1 / (2T rs ) and the estimated Doppler frequency f d_VFT In contrast to this, in this embodiment, the Doppler determination unit 213 calculates the distance index f b_cfar (2) Separation index information of Doppler multiplexed signals (f demul_Tx#N1+1 , f demul_Tx# N1+2 , ~,f demul_Tx#Nt ), the Doppler frequency of the target is in the Doppler frequency range -1 / (2T r ) ≦f d_TargetDoppler <1 / (2T r ) and the estimated Doppler frequency f d_VFT The point at which (2) is calculated.

[0452] In this embodiment, the operation of Doppler determination section 213, which differs from the above three points, is the same as in embodiment 1, and therefore a description of this operation will be omitted.

[0453] In addition, similarly to the Doppler determining unit 213 in the first embodiment, rs " to "T r " The center frequency f that satisfies any of the determination conditions of equations (10) to (15) c (1) and f c By setting (2), the Doppler determination unit 213 determines the Doppler frequency range −1 / (2T r ) ≦ f d_TargetDoppler <1 / (2T r ), the Doppler frequency of the target can be determined even when the target includes a target with a Doppler frequency exceeding T (for example, when Doppler aliasing occurs). rs However, by transforming the equation, T such as equation (11), equation (12), equation (14), and equation (15) can be obtained. rs Therefore, the center frequency f that satisfies the decision condition is c (1) and f c (2) is the same condition as in the first embodiment.

[0454] In addition, the equation (18) used in the explanation of the first embodiment is T rs T r By substituting the above, it is expressed as the following equation (64).

number

[0455] Equation (64) is the Doppler aliasing number n al When the center frequency f c (2) The Doppler frequency aliasing component n observed using the second chirp signal al ×{f c (2) / f c (1)} / T r and the number of times n of foldback of the first Doppler analyzer 210. al The frequency interval is n al / T r The difference is ±1 / (2T r ) is not exceeded. For example, al If is positive, the largest n that satisfies equation (19) alUntil Δn al is ±1 / (2T r ), and the Doppler determination unit 213 can estimate the aliasing without ambiguity. al "n almax For example, n al If is negative, n al =-n almax Then, equation (19) is satisfied as well.

[0456] In the first embodiment, the first chirp signal or the second chirp signal is T rs The Doppler frequency detection range is, for example, n almax On the other hand, in this embodiment, the first chirp signal and the second chirp signal are amplified by T r Since the Doppler frequency is transmitted periodically, the detection range of the Doppler frequency is, for example, 2×n for the Doppler frequency range of one transmitting antenna. almax Therefore, in this embodiment, compared to the first embodiment, the center frequency f of the same chirp signal is c (1) and f c For condition (2), the detection range of the Doppler frequency can be further expanded.

[0457] For example, f c (1) and f c (2) is n almax If the condition for =1 is satisfied, the Doppler frequency f d The detection range of is ±1 / (T r ) and the Doppler frequency range for one transmitting antenna is ±1 / (2T r ) is magnified by a factor of 2. For example, c (1) and f c (2) is n almax If the condition for =2 is satisfied, the Doppler frequency f d The detection range of is ±2 / (T r ) and the Doppler frequency range for one transmitting antenna is ±1 / (2T r ) is magnified by four times.

[0458] An example of the operation of Doppler determination section 213 has been described above.

[0459] [Example of operation of direction estimation unit 214] In FIG. 11, the direction estimation unit 214 receives information (for example, a distance index f b_cfar (1) and the distance index f b_cfar Separation index information (f demul_Tx#1 , f demul_Tx#2 ,~, f demul_Tx#N1 )), and information input from the second Doppler demultiplexing unit 212 (for example, distance index f b_cfar (2) and the distance index f b_cfar (2) Separation index information of Doppler multiplexed signals (f demul_Tx#N1+1 , f demul_Tx#N1+2 ,~, f demul_Tx#Nt )), the output of the first Doppler analysis unit 210 and the output of the second Doppler analysis unit 210 are extracted, and target direction estimation processing is performed.

[0460] In this embodiment, N1×N3 MIMO virtual receive antennas are configured between the N1 transmit antennas 106 included in the first transmit subblock and the N3 receive antennas 202 included in the first receive subblock. Similarly, N2×N4 MIMO virtual receive antennas are configured between the N2 transmit antennas 106 included in the second transmit subblock and the N4 receive antennas 202 included in the second receive subblock. The direction estimation unit 214 may perform direction estimation processing using these two pairs of virtual receive antennas.

[0461] For example, the direction estimation unit 214 derives a distance index f b_cfar (1) and the separation index information of the Doppler multiplexed signal (f demul_Tx#1 , f demul_Tx#2 ,~, f demul_Tx#N1), the output of the first Doppler analyzer 210 is extracted, and a first virtual receiving array correlation vector h1(f b_cfar (1), f demul_Tx#1 , f demul_Tx#2 ,~, f demul_Tx#N1 )

number

[0462] Furthermore, the direction estimation unit 214 calculates, for example, a distance index f b_cfar (2) and the separation index information of the Doppler multiplexed signal (f demul_Tx#N1+1 , f demul_Tx#N1+2 ,~, f demul_Tx#Nt ), the output of the second Doppler analyzer 210 is extracted, and a second virtual receiving array correlation vector h2(f b_cfar (2), f demul_Tx#N1+1 , f demul_Tx#N1+2 ,~, f demul_Tx#Nt )

number

[0463] Note that the direction estimation unit 214 performs direction estimation processing using the outputs of the first and second Doppler demultiplexing units 212 with the same distance index, so in equations (65) and (66), f b_cfar (1)=f b_cfar (2)=f b_cfar Let's say.

[0464] In equation (65), h 1cal[b] is an array correction value that corrects the phase deviation and amplitude deviation between the transmitting antennas Tx#1 to Tx#N1 and between the receiving antennas Rx#1 to #N3, where b is an integer between 1 and (N3×N1).

[0465] Also, in equation (66), h 2cal[b]is an array correction value that corrects the phase deviation and amplitude deviation between the transmitting antennas Tx#N1+1 to Tx#Nt and between the receiving antennas Rx#N3+1 to #Na, where b is an integer between 1 and (N4×N2).

[0466] The direction estimation unit 214 calculates, for example, a direction estimation evaluation function value P H (θ u , f b_cfar , f demul_Tx#1 , f demul_Tx#2 ,~, f demul_Tx#Nt ) azimuth direction θ u is varied within a predetermined angle range to calculate a spatial profile. The direction estimation unit 214 extracts a predetermined number of maximum peaks from the calculated spatial profile in descending order of magnitude, and outputs the azimuth direction of the maximum peak as an estimated direction of arrival value (for example, positioning output). b_cfar is f b_cfar (1)=f b_cfar (2) represents the distance index.

[0467] The direction estimation evaluation function value P H (θ u , f b_cfar , f demul_Tx#1 , f demul_Tx#2 ,~, f demul_Tx#Nt There are various methods for estimating the direction of arrival (DOA) depending on the algorithm. For example, the estimation method using an array antenna disclosed in Non-Patent Document 3 may be used.

[0468] For example, the beamformer method can be expressed as in the following equation (67): In addition to the beamformer method, methods such as Capon and MUSIC can also be applied. In equation (67), the superscript H is the Hermitian transpose operator.

number

[0469] In equation (67), a1(θ u) represents a direction vector (a column vector with N1×N3 elements) of the N1×N3 MIMO virtual receiving antennas configured between the N1 transmitting antennas 106 included in the first transmitting sub-block and the N3 receiving antennas 202 included in the first receiving sub-block, and θ u It represents the phase response or complex amplitude response at each of the N1 × N3 MIMO virtual receiving antennas when a reflected wave arrives from a direction.

[0470] Similarly, in equation (67), a2(θ u ) represents a direction vector (a column vector with N2 × N4 elements) of N2 × N4 MIMO virtual receiving antennas configured between the N2 transmitting antennas 106 included in the second transmitting sub-block and the N4 receiving antennas 202 included in the second receiving sub-block, and θ u It represents the phase response or complex amplitude response at each virtual receiving antenna constituting the N2 × N4 MIMO virtual receiving antennas when a reflected wave arrives from a direction.

[0471] In addition, the direction vector a q (θ u ) is the center frequency f c The phase response or complex amplitude response at each virtual receiving antenna when the wavelength of the radar transmission signal (e.g., the qth chirp signal) in case (q) is used may be used. Alternatively, the center frequency f c (1) and f c (2) The direction vector a(θ) of the virtual receiving array for the arriving wave in the azimuth direction θ at the mean center frequency u ) may be used in common.

[0472] Also, the azimuth direction θ u is a vector obtained by varying the azimuth range for estimating the direction of arrival at a predetermined azimuth interval β1. For example, θ u is set as follows: θ u =θmin + uβ1, integer u=0~ NU NU=floor[(θmax-θmin) / β1]+1 Here, floor(x) is a function that returns the largest integer value that does not exceed the real number x.

[0473] In the above example, the direction estimation unit 214 calculates the azimuth direction as the arrival direction estimated value, but the present invention is not limited to this, and the arrival direction can be estimated in the elevation angle direction, or in the azimuth direction and elevation angle direction by using MIMO antennas arranged in a rectangular grid. For example, the direction estimation unit 214 may calculate the azimuth direction and elevation angle direction as the arrival direction estimated value and output them as positioning outputs.

[0474] By the above operation, the direction estimation unit 214 outputs the distance index f b_cfar , separation index information of Doppler multiplex signals (f demul_Tx#1 , f demul_Tx#2 , ~,f demul_Tx#Nt ) as a positioning output. b_cfar , separation index information of Doppler multiplex signals (f demul_Tx#1 , f demul_Tx#2 , ~,f demul_Tx#Nt The direction estimation unit 214 may output the positioning output (or the positioning result) to, for example, a vehicle control device (not shown) in the case of an in-vehicle radar, or to an infrastructure control device (not shown) in the case of an infrastructure radar.

[0475] Further, the direction estimation unit 214 may, for example, use the Doppler frequency information f determined by the Doppler determination unit 213. d_VFT(1) +n alest / T s , and f c (2) / f c (1)(f d_VFT(1) +n alest / T s ) or both may be output.

[0476] Also, the distance index f b_cfar may be converted into distance information using equation (1) and output.

[0477] Furthermore, the Doppler frequency information determined by the Doppler determination unit 213 may be converted into relative velocity information and output. c Doppler frequency information f d_VFT(1) +n alest / T s relative velocity v d To convert it into:

number

[0478] Similarly, the center frequency f determined by the Doppler determination unit 213 c (2) Doppler frequency information f c (2) / f c (1)(f d_VFT(1) +n alest / T r ) relative velocity v d When converted into the following equation (69), the same value as equation (68) is obtained, so the relative velocity component information may be output as a common value (or a unified value) for different center frequencies.

number

[0479] As described above, in this embodiment, the radar device 10a includes a plurality of radar transmission signal generators 101, and transmits a transmission signal from the transmitting antenna 106 at each predetermined transmission period using, for example, a first center frequency and a second center frequency that satisfy any one of Equations (10) to (15). This allows the radar device 10a to determine the number of aliases in the Doppler determination unit 213 based on the deviation in Doppler frequency detected in the Doppler analysis unit 210 and the Doppler demultiplexing unit 212, which corresponds to the difference in center frequency. Therefore, the radar device 10a can expand the Doppler frequency range (or the maximum value of the relative velocity) in which a Doppler multiplexed signal can be separated, for example, depending on the number of aliases that can be determined.

[0480] In this embodiment, the first chirp signal and the second chirp signal are transmitted with a transmission period T r Since the signals are transmitted simultaneously, the Doppler frequency range is ±1 / 2T. r For example, in the first embodiment, the Doppler multiplexed signal can be multiplexed within the range of T rs =2T r In comparison with the case where Doppler multiplexed transmission is performed in a Doppler frequency range (or maximum value of relative velocity) twice as wide, in this embodiment, Doppler multiplexed signals can be multiplexed and transmitted in a Doppler frequency range twice as wide (or maximum value of relative velocity).

[0481] Furthermore, for example, by making the number of transmitting antennas 106 included in the first and second transmitting sub-blocks the same or approximately the same, the Doppler multiplexing interval when Doppler multiplexing using the first chirp signal and the second chirp signal can be expanded by approximately four times compared to embodiment 1.

[0482] Note that if the Doppler multiplexing intervals during Doppler multiplexing are close to each other, interference between Doppler multiplexed signals is likely to occur in the case of targets with spread Doppler components, which can degrade the direction estimation accuracy and target detection accuracy. In this embodiment, the Doppler multiplexing interval during Doppler multiplexing can be extended compared to embodiment 1, thereby reducing the occurrence of such interference between Doppler multiplexed signals and suppressing deterioration in direction estimation accuracy and target detection accuracy. Furthermore, in this embodiment, the Doppler multiplexing interval during Doppler multiplexing can be extended compared to embodiment 1, thereby reducing the occurrence of interference between Doppler multiplexed signals and suppressing deterioration in direction estimation accuracy and target detection accuracy even when more transmitting antennas are used for Doppler multiplexing. Therefore, in this embodiment, Doppler multiplexing transmission using more transmitting antennas 106 is possible compared to embodiment 1.

[0483] As described above, according to this embodiment, the Doppler frequency range (or the maximum value of the relative velocity) in which no ambiguity occurs can be expanded, and the radar device 10a can thereby detect targets (e.g., arrival directions) with high accuracy in a wider Doppler frequency range.

[0484] Furthermore, in this embodiment, the Doppler frequency range in which Doppler multiplexed signals can be separated is expanded by setting the center frequency of the chirp signal, so it is possible to omit applying a method such as increasing the sampling rate of the A / D converter. Therefore, according to this embodiment, it is possible to suppress the complexity of the hardware configuration of the radar device 10a and also to suppress an increase in the power consumption or heat generation of the radar device 10a. Furthermore, in this embodiment, the Doppler frequency range in which Doppler multiplexed signals can be separated is expanded by setting the center frequency of the chirp signal, so it is possible to omit applying a method such as increasing the sampling rate of the A / D converter. r Therefore, according to this embodiment, it is possible to suppress a reduction in the detectable distance range of the radar device 10a or a deterioration in distance resolution.

[0485] In the present embodiment, the radar device 10a includes two radar transmission signal generators 101, and transmits a transmission signal from the transmitting antenna 106 at predetermined transmission intervals using a first center frequency and a second center frequency that satisfy any one of equations (10) to (15). However, the present invention is not limited to this. The radar device 10a may include, for example, more radar transmission signal generators 101 (three or more).

[0486] For example, the radar device 10a includes three radar transmission signal generation units 101, uses a first center frequency fc(1) and a second center frequency fc(2) that satisfy any of equations (10) to (15), and further uses a second center frequency fc(2) and a third center frequency fc(3) that satisfy any of equations (10) to (15) to transmit a transmission signal from the transmission antenna 106 every predetermined transmission period. Note that fc(1)>fc(2)>fc(3) or fc(1)<fc(2)<fc(3) may be set. In this case, in the radar receiving unit 200a, three receiving sub-blocks are provided, and the outputs from the three radar transmission signal generation units 101 may be respectively input to the mixer units 204 of the respective receiving sub-blocks. Also, in the radar receiving unit 200a, a CFAR unit 211 and a Doppler multiplex separation unit 212 are provided for each receiving sub-block, and they may perform the same operations as in the present embodiment. Thereby, a multiplex separation received signal for three chirp signals is obtained, and the Doppler determination unit 213 can expand the detection range of the Doppler frequency by performing Doppler determination based on those output signals.

[0487] Also, for example, the radar device 10a may be configured to include three or more radar transmission signal generation units 101, and the number of transmission antennas included in each transmission sub-block may be the same or approximately the same. Thereby, an effect of further expanding the Doppler multiplexing interval when performing Doppler multiplexing using a plurality of chirp signals is obtained. Therefore, since the Doppler multiplexing interval when performing Doppler multiplexing can be expanded, the occurrence of interference between Doppler multiplexed signals can be reduced, and deterioration of direction estimation accuracy and deterioration of target detection accuracy due to interference can be suppressed. Also, since the Doppler multiplexing interval when performing Doppler multiplexing can be expanded, compared with the first embodiment, even if more transmission antennas 106 are used for Doppler multiplexed transmission, the occurrence of interference between Doppler multiplexed signals can be reduced, and deterioration of direction estimation accuracy and deterioration of target detection accuracy can be suppressed.

[0488] In addition, in the present embodiment, the case where the modulation parameters for the first chirp signal and the second chirp signal have other parameters other than the center frequency in common has been described, but this is not limiting. To apply an embodiment of the present disclosure, it is sufficient that the distance resolution is the same, and the frequency sweep bandwidth B w It is sufficient if the chirp signals have the same relationship as (q).

[0489] For example, as shown in Figure 15, w (1)=B w (2), T sw (1)≠T sw (2), D m (1)≠D m (2) may be used. In this case, the frequency sweep time T SW Although the frequency sweep bandwidth B w is the same, and the distance resolution ΔR (= C0 / 2B w ) match, the radar device 10a can obtain the same effect by performing the operation according to the embodiment of the present disclosure described above.

[0490] Also, for example, as shown in FIG. sw (1)≠T sw By setting (2), when the beat signal output from each radio receiving unit 203 is discretely sampled in the A / D conversion unit 207 of each signal processing unit 206, a predetermined time range (range gate) T sw (1)≠T sw The number of discrete sampling data obtained in (2) is different. Therefore, the beat frequency analysis unit 208 calculates, for example, the number of discrete sampling data obtained in (2) for the transmission period T r Every predetermined time range (range gate) T sw N obtained by data Instead of performing FFT processing on the discrete sampled data, the following operation may be performed.

[0491] For example, the beat frequency analysis unit 208 in the first reception sub-block analyzes the first chirp signal within a predetermined time range (range gate) T sw N obtained in (1) data The beat frequency analysis unit 208 in the second reception sub-block may perform FFT processing on (1) discrete sampling data. sw N obtained in (2) data (2) The beat frequency analysis unit 208 may perform FFT processing on the discrete sampling data. data (1) Pieces and N data (2) The smaller of these is N data As an individual unit, subsequent processing (processing by the CFAR unit 211, the Doppler demultiplexing unit 212, the Doppler determination unit 213, and the direction estimation unit 214) may be performed.

[0492] Furthermore, the radar device 10a of this embodiment includes a plurality of radar transmission signal generators 101, and transmits a transmission signal from the transmitting antenna 106 at each predetermined transmission period using, for example, a first center frequency and a second center frequency that satisfy any one of equations (10) to (15). This allows the radar device 10a to determine the number of aliasings based on the deviation of the Doppler frequency in Doppler analysis according to the difference in center frequency. Therefore, the radar device 10a can expand the Doppler frequency range (or the maximum value of relative velocity) in which Doppler-multiplexed signals can be separated, for example, according to the number of aliasings that can be determined. Furthermore, compared to the first embodiment, the Doppler frequency range (or the maximum value of relative velocity) in which Doppler-multiplexed signals can be separated can be expanded by two times.

[0493] Furthermore, in this embodiment, the Doppler detection range in Doppler analysis unit 210 is twice as large as in the first embodiment. Furthermore, in this embodiment, the number of transmitting antennas N1 or N2 used for Doppler multiplexing is smaller than the number of transmitting antennas Nt used for Doppler multiplexing in the first embodiment. As a result, in this embodiment, the Doppler multiplexing interval can be increased at least twice as large as in the first embodiment. For example, if the Doppler multiplexing interval is close, interference between Doppler multiplexed signals is more likely to occur in the case of targets with spread Doppler components. In contrast, in this embodiment, multiplexing and transmission can be performed using a larger number of transmitting antennas 106.

[0494] (Modification 1 of Embodiment 3) In this embodiment, the Doppler shift units 105-1 to 105-N1 and the Doppler shift units 105-N1+1 to 105-Nt included in the first and second transmission sub-blocks calculate the Doppler shift amounts DOP for the first and second chirp signals, respectively. nsub1 , DOP nsub2 The operation has been described in the case where the intervals between the Doppler shift signals (Doppler shift intervals) are not set to equal intervals, but at least one Doppler interval is set to an unequal interval.

[0495] However, this is not limited to this, and at least one of the Doppler intervals set by Doppler shift unit 105 in the first or second transmission sub-block may be set to different unequal intervals rather than to equal intervals, and the other may be set to equal intervals.

[0496] As an example, the Doppler shift units 105-1 to 105-N1 included in the first transmission sub-block perform a Doppler shift amount DOP that differs from one another for the input m-th first chirp signal. nsub1 The phase rotation φ as shown in Eq. (62) nsub1Here, we will explain the case where unequal interval Doppler multiplexing is performed with a Doppler multiplexing number N1, where (m) is assigned. In this case, the Doppler shift units 105-N1+1 to 105-Nt included in the second transmission sub-block perform Doppler shifts DOP that differ from one another for the m-th second chirp signal input. nsub2 The phase rotation φ as shown in the following equation (70) nsub2 (m) and perform equal-interval Doppler multiplexing with a Doppler multiplexing number N2.

number

[0497] Alternatively, as another example, the Doppler shift units 105-1 to 105-N1 included in the first transmission sub-block perform a Doppler shift amount DOP that differs between the Doppler shift units 105 for the m-th input first chirp signal. nsub1 The phase rotation φ as shown in the following equation (71) nsub1 The following describes a case where the Doppler multiplexing number is N1, and the Doppler shift units 105-N1+1 to 105-Nt included in the second transmission sub-block assign different Doppler shift amounts DOP nsub2 The phase rotation φ as shown in Eq. (63) nsub2 (m) may be added, and non-uniform Doppler multiplexing may be performed with a Doppler multiplexing number N2.

number

[0498] In the formulas (70) and (71), A is a coefficient that gives the positive or negative polarity of 1 or -1. C / N1) and round(N C The term (2π / N2) is introduced for the purpose of making the phase rotation amount an integer multiple of the Doppler frequency interval in the Doppler analysis unit 210. However, the present invention is not limited to this, and the term (2π / N C )×round(N CSimilarly, the term (2π / N C )×round(N C Instead of the term φ, 2π / N2 may be used. 01 , φ 02 are the initial phases, and may be equal or different. 01 , φ 02 Whether they are equal or different, the Doppler frequencies will be the same. 01 , Δφ 02 are reference Doppler shift phases, which may be equal or different. 01 , Δφ 02 Whether they are equal or different, the Doppler frequencies will match.

[0499] As an example of the case where the number of transmitting antennas is Nt=4, in equation (62), N1=2, Δφ 01 =0, φ 01 =0, A=1, δ1=1, N C is a multiple of 6, and the phase rotation φ nsub1 (m)=2π(nsub1-1)×(m-1) / 3 is the transmission period T r Since the first chirp signal is added every 100 m, the Doppler shift is DOP1 = φ1(m) / {2π(m-1)T r}=0, DOP2=φ2(m) / {2π(m-1)T r}=1 / (3T r The upper part of (a) of FIG. 16 shows an example of arrangement of Doppler multiplexed signals when transmitting the first chirp signal.

[0500] As an example of the case where the number of transmitting antennas is Nt=4, in equation (70), Nt=4, N2=2, Δφ 02 =0, φ 02 =0, A=1, N C is a multiple of 6, and the phase rotation φ nsub2 (m)=2π(nsub2-1)×(m-1) / 2 is the transmission period T r Since the second chirp signal is added every 1 / T, the Doppler shift is DOP1=0, DOP2=1 / T rThe lower part of (a) of Fig. 16 shows an example of arrangement of Doppler multiplexed signals when transmitting the second chirp signal.

[0501] As an example of the case where the number of transmitting antennas is Nt=5, in equation (71), N1=3, Δφ 01 =0, φ 01 =0, A=1, N C If is a multiple of 3, the phase rotation φ nsub1 (m)=2π(nsub1-1)×(m-1) / 3 is the transmission period T r Since the first chirp signal is added every 100 m, the Doppler shift is DOP1 = φ1(m) / {2π(m-1)T r}=0, DOP2=φ2(m) / {2π(m-1)T r}=1 / (3T r ), DOP3=φ3(m) / {2π(m-1)T r}=2 / (3T r ) =-1 / (3T r The upper part of (b) of FIG. 16 shows an example of the arrangement of Doppler multiplexed signals when transmitting the first chirp signal.

[0502] As an example of the case where the number of transmitting antennas is Nt=5, in equation (63), Nt=5, N2=2, Δφ 02 =0, φ 02 =0, A=1, δ2=1, N C If is a multiple of 3, the phase rotation φ nsub2 (m)=π×(m-1) / 2 is the transmission period T r Since the second chirp signal is added every 100 ms, the Doppler shift is DOP1=0, DOP2=1 / (3T r The bottom part of (b) of FIG. 16 shows an example of the arrangement of Doppler multiplexed signals when transmitting the second chirp signal.

[0503] In this way, when the Doppler intervals between the Doppler multiplexed signals set in the Doppler shifter 105 in the first or second transmission sub-block are set to equal intervals, the Doppler multiplexer 212 in the radar receiver 200a performs a Doppler separation of ±1 / T rIn this Doppler frequency range, it is difficult to estimate the Doppler frequency, and therefore it is difficult to output separation index information for the Doppler multiplexed signal. The radar receiver 200a performs separation processing using the output of the Doppler demultiplexer 212 for received signals corresponding to signals of transmission sub-blocks in which the Doppler intervals between Doppler multiplexed signals set in the Doppler shifter 105 in the first or second transmission sub-block are unequal.

[0504] FIG. 17 shows an example of the configuration of a radar receiver 200a in a radar device 10a in which the Doppler shifter 105 in the first transmission sub-block performs unequal Doppler multiplexing and the Doppler shifter 105 in the second transmission sub-block performs equal Doppler multiplexing.

[0505] The first receiving sub-block performs receiving processing on the reflected waves of the first transmitting sub-block. The radar receiving unit 200a shown in Fig. 17 differs from the configuration of the radar receiving unit 200a shown in Fig. 11 in that, for example, the output from the first Doppler demultiplexing unit 212 is input to the second Doppler demultiplexing unit 212. Below, an example of the operation of the Doppler demultiplexing unit 212 in the radar receiving unit 200a shown in Fig. 17, which differs from the radar receiving unit 200a shown in Fig. 11, will be described.

[0506] The operation of separating the Doppler multiplexed signal in the first Doppler multiplex separation unit 212 is the same as the operation described above (operation in FIG. 11), but the first Doppler multiplex separation unit 212 separates the Doppler multiplexed signal using the distance index f b_cfar (1) Information and distance index f b_cfar Separation index information (f demul_Tx#1 , f demul_Tx#2 ,~, f demul_Tx#N1 ) to the second Doppler demultiplexing unit 212.

[0507] The second Doppler demultiplexing unit 212 demultiplexes, for example, the distance index f b_cfar Separation index information (fdemul_Tx#1 , f demul_Tx#2 ,~,f demul_Tx#Nt ), the Doppler frequency of the target is in the Doppler frequency range -1 / (2T r ) ≦f d_TargetDoppler <1 / (2T r ) and the estimated Doppler frequency f d_VFT For example, the second Doppler demultiplexing unit 212 calculates the Doppler frequency estimated value f d_VFT (1) may be calculated.

[0508] Then, the second Doppler demultiplexing unit 212 extracts the calculated Doppler frequency estimate f d_VFT Based on (1), the peak (distance index f b_cfar (2) and the Doppler frequency index f s_cfar For example, the second Doppler multiplexing demultiplexing unit 212 separates the Doppler multiplexed signals using the distance index f b_cfar (1)=f b_cfar (2) Multiple Doppler frequency indexes f s_cfar (2) ∈{fd #N1+1 ,fd #N1+2 …,fd #Nt}, the Doppler frequency estimate f d_VFT Using (1), it is determined which of the transmission signals transmitted from the transmission antennas Tx#N1+1 to Tx#Nt the reflected wave signal corresponds to.

[0509] For example, the Doppler shift amount that the Doppler shifter 105 in the second transmission sub-block applies to each of the second chirp signals output from the transmitting antennas Tx#N1+1 to Tx#Nt is known. Therefore, the second Doppler demultiplexer 212 calculates the Doppler frequency of the target based on the Doppler frequency estimated value f d_VFT Assuming the case (1), it is possible to calculate the reception Doppler frequencies for the transmitting antennas Tx#N1+1 to Tx#Nt.

[0510] In this case, each of the receiving Doppler frequencies for the transmitting antennas Tx#N1+1 to Tx#Nt is expressed as {fdRef #N1+1 ,fdRef #N1+2 ,~,fdRef #Nt}.

[0511] The second Doppler demultiplexing unit 212 can generate signals for each of the transmit antennas 106. For example, the second Doppler demultiplexing unit 212 uses each Doppler frequency index f s_cfar (2) The difference is the smallest and ±ΔDOP min2 Doppler frequencies smaller than 1 / 2 are determined to be reception Doppler frequencies for the transmitting antennas Tx#N1+1 to Tx#Nt.

[0512] Then, the second Doppler demultiplexing unit 212 separates and outputs the reflected wave signals for each of the determined transmitting antennas Tx#N+1 to Tx#Nt. For example, the second Doppler demultiplexing unit 212 separates and outputs the reflected wave signals for each of the determined transmitting antennas Tx#N+1 to Tx#Nt. b_cfar (2) Information, distance index f b_cfar Separation index information (f demul_Tx#N1+1 , f demul_Tx#N1+2 ,~, f demul_Tx#Nt ), and outputs the output of the Doppler analysis unit 210 to the Doppler determination unit 213.

[0513] The second Doppler demultiplexing unit 212 is capable of operating as described above if the difference in the Doppler frequency of the target caused by the difference between the center frequency of the first chirp signal and the center frequency of the second chirp signal is ±ΔDOP. min2 / 2, the relative velocity of the target is assumed to be within this range.

[0514] 17, in the radar device 10a, the Doppler shift unit 105 in the second transmission sub-block may perform uneven Doppler multiplexing, and the Doppler shift unit 105 in the first transmission sub-block may perform equal Doppler multiplexing. In this case, as in the example of FIG. 17, in the radar receiving unit 200a, the output from the second Doppler demultiplexing unit 212 is input to the first Doppler demultiplexing unit 212, thereby enabling Doppler demultiplexing in the first Doppler demultiplexing unit 212.

[0515] In this way, the Doppler shift unit 105 in at least one of the first or second transmission sub-blocks may be set to perform uneven Doppler multiplexing, and the Doppler shift unit 105 in the remaining transmission sub-blocks may be set to perform even Doppler multiplexing. This allows the radar device 10a to achieve the effect of further increasing the Doppler multiplexing interval when Doppler multiplexing using the first chirp signal and the second chirp signal. By increasing the Doppler multiplexing interval when Doppler multiplexing, it is possible to reduce the occurrence of interference between Doppler-multiplexed signals and suppress deterioration in direction estimation accuracy and target detection accuracy. Note that the settings of uneven Doppler multiplexing and even Doppler multiplexing can be similarly applied to the Doppler shift unit 105 in the following embodiments, and similar effects can be achieved.

[0516] (Modification 2 of Embodiment 3) 11 may be realized by combining a plurality of transmitting and receiving chips, as shown in Fig. 18. In the example of Fig. 18, the radar device 10a is configured from a transmitting and receiving chip #1 and a transmitting and receiving chip #2.

[0517] The transmit / receive chip #q includes a radar transmission signal generation unit 101-q, a q-th transmission sub-block, a q-th reception sub-block, a q-th CFAR unit 211 (or a CFAR unit 211-q), and a q-th Doppler demultiplexing unit 212 (or a Doppler demultiplexing unit 212-q), where q=1 or 2.

[0518] At least one of the Doppler determination unit 213 and the direction estimation unit 214 may be implemented on a separate signal processing chip or ECU, or may be incorporated into either the transmission / reception chip.

[0519] 18 differs from FIG. 11 in that a synchronization signal generator 215 is provided, and a synchronization signal (e.g., a reference signal) output from the synchronization signal generator 215 is output to the radar transmission signal generator 101 of the radar transmitter 100a of each transmit / receive chip. This makes it possible to output chirp signals so that the frequency difference between the first chirp signal output from the transmit sub-block of transmit / receive chip #1 and the second chirp signal output from the transmit sub-block of transmit / receive chip #2 is within a predetermined allowable error range. The configuration shown in FIG. 18 also achieves the same effects as the third embodiment, and by combining general-purpose transmit / receive chips, costs can be reduced.

[0520] (Fourth embodiment) In the third embodiment, a MIMO antenna configuration is used with Nt transmitting antennas and Na receiving antennas, and the direction estimation unit 214 performs direction estimation processing using N1×N3 MIMO virtual receiving antennas and N2×N4 MIMO virtual receiving antennas. Here, N1+N2=Nt and N3+N4=Na. In this case, the number of antennas available in the direction estimation unit 214 is less than Nt×Na.

[0521] In this embodiment, a method will be described in which the number of MIMO virtual receive antennas available in the direction estimation unit 214 is set to Nt×Na, as in the first embodiment, when radar transmit signals of different frequencies are simultaneously transmitted in each transmission period, as in the third embodiment.

[0522] For example, Fig. 19 shows a configuration example in which the radar transmitter 100b of the radar device 10b includes two radar transmission signal generators 101. As shown in Fig. 19, the radar device 10b, like the configuration of the radar device 10a shown in Fig. 11 in the third embodiment, transmits radar transmission signals (for example, chirp signals) with different center frequencies generated in the multiple radar transmission signal generators 101 at a transmission period T r The signals are simultaneously transmitted from multiple transmitting antennas 106 for each channel.

[0523] 19 differs from that of FIG. 11 in that it includes a switching unit 216 that switches the output destination of the multiple radar transmission signal generation units 101 to one of the mixer units 204 in the two reception sub-blocks. The radar reception unit 200b shown in FIG. 19 also includes an output switching unit 217 that, in conjunction with the switching operation of the switching unit 216, switches the output destination of the beat frequency analysis unit 208 to one of the two Doppler analysis units 210 for output.

[0524] The following describes the operation of this embodiment, focusing mainly on examples of operation that differ from that of the third embodiment.

[0525] 19 shows, as an example, a configuration in which the radar transmitter 100b of the radar device 10b includes two radar transmission signal generators 101. Hereinafter, the two radar transmission signal generators 101 are referred to as the "first radar transmission signal generator 101 (or radar transmission signal generator 101-1)" and the "second radar transmission signal generator 101 (or radar transmission signal generator 101-2)."

[0526] 19, the configuration of each radar transmission signal generator 101 may be the same as that in Embodiment 1. Each radar transmission signal generator 101 generates a radar transmission signal under the control of, for example, a signal generation controller 104.

[0527] The signal generation control unit 104 controls the generation of radar transmission signals by the first and second radar transmission signal generation units 101 (e.g., the modulation signal generation unit 102 and the VCO 103). For example, the signal generation control unit 104 may set parameters (e.g., modulation parameters) related to the chirp signals so that the first and second radar transmission signal generation units 101 transmit chirp signals with different center frequencies. Hereinafter, the chirp signal generated in the first radar transmission signal generation unit 101 will be referred to as the "first chirp signal," and the chirp signal generated in the second radar transmission signal generation unit 101 will be referred to as the "second chirp signal."

[0528] As in the first embodiment, the signal generation control unit 104 selects, for example, a center frequency f c In the following, as an example, among the modulation parameters set for the first chirp signal and the second chirp signal, the center frequency f c The following describes a case where (q) is different from each other and other modulation parameters other than the center frequency are the same (or common). However, this is not limited to this. For application of an embodiment of the present disclosure, for example, it is sufficient that the resolution of the distance axis in the first chirp signal and the second chirp signal is the same. Therefore, the frequency sweep bandwidth B w It is sufficient to set chirp signals such that (q) has the same relationship, where q=1, 2.

[0529] Furthermore, the signal generation control unit 104 may, for example, as in the third embodiment, set the center frequency f c The modulation signal generating section 102 and the VCO 103 may be controlled so that each of the two different chirp signals (q) is simultaneously transmitted (or output) 2Nc times.

[0530] In one embodiment of the present disclosure, the transmission period T rmay be set to, for example, several hundred μs or less, and the transmission time interval of the radar transmission signal may be set to a relatively short time. As a result, even if the center frequencies of the first chirp signal and the second chirp signal are different, the frequency of the beat signal of the received reflected wave (e.g., beat frequency index) does not change, and the radar device 10b can detect this as a change in Doppler frequency.

[0531] The first chirp signal output from the first radar transmission signal generation unit 101 (for example, VCO 103) is input to, for example, N1 Doppler shift units 105 (for example, represented as Doppler shift units 105-1 to 105-N1) among the Nt Doppler shift units 105. The first chirp signal output from the first radar transmission signal generation unit 101 is input to, for example, a first switch unit 216 (also referred to as switch unit 216-1) and a second switch unit 216 (also referred to as switch unit 216-2).

[0532] On the other hand, the second chirp signal output from the second radar transmission signal generation unit 101 (e.g., VCO 103) is input to, for example, N2 Doppler shift units 105 (e.g., Doppler shift units 105-N1+1 to 105-Nt) among the Nt Doppler shift units 105. In addition, the second chirp signal output from the second radar transmission signal generation unit 101 is input to the first and second switching units 216.

[0533] Here, N1+N2=Nt.

[0534] Then, the output signals of the N1 Doppler shift units 105 to which the first chirp signal is input are amplified to a predetermined transmission power and radiated into space from each transmitting antenna 106 (for example, Tx#1 to Tx#N1). Also, the output signals of the N2 Doppler shift units 105 to which the second chirp signal is input are amplified to a predetermined transmission power and radiated into space from each transmitting antenna 106 (for example, Tx#N1+1 to Tx#Nt). As a result, the first chirp signal and the second chirp signal are amplified to a predetermined transmission power and radiated into space from each transmitting antenna 106 (for example, Tx#N1+1 to Tx#Nt). r are sent simultaneously every

[0535] The first and second switching units 216, for example, switch between the first chirp signal input from the first radar transmission signal generating unit 101 and the second chirp signal input from the second radar transmission signal generating unit 101 for each transmission period of the radar transmission signal, and output the signal to one of the mixer units 204 of the Na antenna system processing units 201 in the radar receiving unit 200b.

[0536] For example, in odd-numbered transmission periods, the first chirp signal may be input by the first and second switching units 216 to the mixer units 204 of N3 antenna system processing units 201 (e.g., antenna system processing units 201-1 to 201-N3) among the Na antenna system processing units 201 in the radar receiving unit 200b. Also, for example, in odd-numbered transmission periods, the first and second switching units 216 may be input by the second chirp signal to the mixer units 204 of N4 antenna system processing units 201 (e.g., antenna system processing units 201-N3+1 to 201-Na) among the Na antenna system processing units 201 in the radar receiving unit 200b.

[0537] Here, N3+N4=Na.

[0538] Furthermore, for example, in an even-numbered transmission period, the first chirp signal may be input to the mixer units 204 of N4 antenna system processing units 201 (e.g., antenna system processing units 201-N3+1 to 201-Na) among the Na antenna system processing units 201 of the radar receiving unit 200b by the first and second switching units 216. Furthermore, for example, in an even-numbered transmission period, the second chirp signal may be input to the mixer units 204 of N3 antenna system processing units 201 (e.g., antenna system processing units 201-1 to 201-N3) among the Na antenna system processing units 201 of the radar receiving unit 200b.

[0539] The output destinations of the first and second chirp signals (the switching destinations of the first and second switching units 216) in odd-numbered and even-numbered transmission periods may be reversed. In this way, the output destinations of the first and second chirp signals (receiving sub-blocks, described later) may be switched alternately for each transmission period.

[0540] Hereinafter, the N1 Doppler shift units 105 to which the first chirp signal is input and the respective transmit antennas 106 (e.g., Tx#1 to Tx#N1) that transmit the output signals of these N1 Doppler shift units 105 are referred to as the "first transmit sub-block." Also, the N2 Doppler shift units 105 to which the second chirp signal is input and the respective transmit antennas 106 (e.g., Tx#N1+1 to Tx#Nt) that transmit the output signals of these N2 Doppler shift units 105 are referred to as the "second transmit sub-block." Here, N1+N2=Nt. Note that N1 and N2 are each 2 or more, and Nt is 4 or more.

[0541] For example, the Doppler shift unit 105 included in the first transmission sub-block shifts the first chirp signal by a transmission period T r Doppler shift amount DOP nsub1 To give the phase rotation φ nsub1 and outputs the Doppler-shifted signal to the transmitting antennas 106 (for example, Tx#1 to Tx#N1). Here, nsub1 is an integer between 1 and N1. Furthermore, the Doppler shifter 105 included in the second transmitting sub-block applies a transmission period T r Doppler shift amount DOP nsub2 To give the phase rotation φ nsub2 and outputs the Doppler-shifted signal to a transmitting antenna 106 (for example, Tx#N1+1 to Tx#Nt), where nsub2 is an integer between 1 and N2.

[0542] The Doppler shift amount DOP in the Doppler shift unit 105 included in the first and second transmission sub-blocks is nsub1 (or phase rotation φ nsub1 ), and the Doppler shift DOP nsub2(or phase rotation φ nsub2 ) is different from that in the third embodiment, and an example thereof will be described later.

[0543] Furthermore, when Nt is an even number, the first and second transmission sub-blocks may have the same number of transmitting antennas 106, for example, by setting N1 = N2. When Nt is an odd number, the first and second transmission sub-blocks may have the same number of transmitting antennas 106, for example, by setting N1 = (Nt + 1) / 2 or N1 = (Nt - 1) / 2. In this way, the number of transmitting antennas 106 included in the first sub-block (e.g., transmitting antennas 106 transmitting the first chirp signal) and the number of transmitting antennas 106 included in each second transmission sub-block (e.g., transmitting antennas 106 transmitting the second chirp signal) may be set to be the same or different by one. By setting the number of transmitting antennas 106 included in the first and second sub-blocks to be equal or approximately equal, the radar device 10b can obtain an effect of further increasing (for example, approximately doubling) the Doppler multiplexing interval when performing Doppler multiplexing using the first chirp signal and the second chirp signal, compared to the first embodiment.

[0544] For example, if the Doppler multiplex interval during Doppler multiplex transmission is close, in the case of a target with a spread in Doppler components, interference between the Doppler multiplexed signals is likely to occur, degrading the direction estimation accuracy and target detection accuracy. In this embodiment, the Doppler multiplex interval during Doppler multiplexing can be extended, thereby reducing the occurrence of such interference between Doppler multiplexed signals and suppressing degradation of the direction estimation accuracy and target detection accuracy.

[0545] Furthermore, in this embodiment, since the Doppler multiplexing interval during Doppler multiplexing can be extended, even if more transmitting antennas 106 are used for Doppler multiplexing, it is possible to reduce the occurrence of interference between Doppler multiplexed signals and suppress deterioration in direction estimation accuracy and target detection accuracy. Therefore, in this embodiment, more transmitting antennas 106 can be used for Doppler multiplexing compared to embodiment 1. In this way, when Doppler multiplexing is performed using more transmitting antennas 106, this embodiment is more preferable than embodiment 1.

[0546] [Configuration example of radar receiver 200b] 19, the radar receiver 200b includes, for example, Na receiving antennas 202 (for example, Rx#1 to Rx#Na) to form an array antenna. The radar receiver 200b also includes, for example, Na antenna system processors 201-1 to 201-Na, a CFAR unit 211, a Doppler demultiplexing unit 212, a Doppler determination unit 213, and a direction estimation unit 214.

[0547] Each receiving antenna 202 receives a reflected wave signal, which is a radar transmission signal (e.g., a first chirp signal and a second chirp signal) reflected from a target, and outputs the received reflected wave signal to the corresponding antenna system processing unit 201 as a received signal.

[0548] Each antenna system processing unit 201 includes a receiving radio unit 203 and a signal processing unit 206 .

[0549] The radio reception unit 203 has a mixer unit 204 and an LPF 205. In the radio reception unit 203, the mixer unit 204 mixes the received reflected wave signal (received signal) with a chirp signal, which is a transmission signal.

[0550] Here, for example, in an odd-numbered transmission period, the first chirp signal output from the first or second switching unit 216 is input to each of the mixer units 204 in the radio reception units 203 of N3 of the Na antenna system processing units 201. In the antenna system processing units 201-1 to 201-N3, by passing the outputs of the mixer units 204 through the LPFs 205, the output of the mixer units 204 corresponding to the reflected wave of the second chirp signal becomes a high frequency outside the passband of the LPFs 205, and therefore the LPFs 205 tend to output a beat signal having a frequency corresponding to the delay time of the reflected wave signal of the first chirp signal.

[0551] Furthermore, for example, in odd-numbered transmission periods, the second chirp signal output from the first or second switching unit 216 is input to each of the mixer units 204 in the radio reception units 203 of N4 of the Na antenna system processing units 201. In the antenna system processing units 201-N3+1 to 201-Na, the outputs of the mixer units 204 are passed through the LPFs 205, so that the output of the mixer units 204 corresponding to the reflected wave of the first chirp signal has a high frequency outside the passband of the LPFs 205. Therefore, the LPFs 205 tend to output a beat signal having a frequency according to the delay time of the reflected wave signal of the second chirp signal.

[0552] On the other hand, for example, in an even-numbered transmission period, the second chirp signal output from the first or second switching unit 216 is input to each of the mixer units 204 in the radio reception units 203 of N3 of the Na antenna system processing units 201. In the antenna system processing units 201-1 to 201-N3, by passing the outputs of the mixer units 204 through the LPFs 205, the output of the mixer units 204 corresponding to the reflected wave of the first chirp signal becomes a high frequency outside the passband of the LPFs 205, and therefore the LPFs 205 are more likely to output a beat signal having a frequency according to the delay time of the reflected wave signal of the second chirp signal.

[0553] Furthermore, for example, in an even-numbered transmission period, the first chirp signal output from the first or second switching unit 216 is input to each of the mixer units 204 in the radio reception units 203 of N4 of the Na antenna system processing units 201. In the antenna system processing units 201-N3+1 to 201-Na, by passing the outputs of the mixer units 204 through the LPFs 205, the output of the mixer units 204 corresponding to the reflected wave of the second chirp signal becomes a high frequency outside the passband of the LPFs 205, and therefore the LPFs 205 tend to output a beat signal having a frequency corresponding to the delay time of the reflected wave signal of the first chirp signal.

[0554] Therefore, antenna system processing units 201-1 to 201-N3 process, for example, reflected wave signals of first chirp signals received by receiving antennas 202-1 to 202-N3 in odd-numbered transmission periods, and process reflected wave signals of second chirp signals received by receiving antennas 202-1 to 202-N3 in even-numbered transmission periods. Hereinafter, antenna system processing units 201 (e.g., reception radio unit 203 and signal processing unit 206) that process reflected waves of first chirp signals in odd-numbered transmission periods and reflected waves of second chirp signals in even-numbered transmission periods, and receiving antennas 202 connected to these antenna system processing units 201, will be referred to as the "first receiving sub-block."

[0555] Furthermore, the antenna system processing units 201-N3+1 to 201-Na process, for example, reflected wave signals of the second chirp signal received by the receiving antennas 202-N3+1 to 202-Na in odd-numbered transmission periods, and process reflected wave signals of the first chirp signal received by the receiving antennas 202-N3+1 to 202-Na in even-numbered transmission periods. Hereinafter, the antenna system processing units 201 (e.g., the reception radio unit 203 and the signal processing unit 206) that process the reflected wave of the second chirp signal in odd-numbered transmission periods and the reflected wave of the first chirp signal in even-numbered transmission periods, and the receiving antennas 202 connected to these antenna system processing units 201, will be referred to as the "second receiving sub-block."

[0556] Here, N3+N4=Na. Note that N3 and N4 may each be 1 or greater, and Na may be 2 or greater.

[0557] For example, the first receiving sub-block (e.g., corresponding to the first receiving circuit) mixes the signal received by the receiving antenna 202 with the first chirp signal in odd-numbered transmission periods to output a reflected wave signal resulting from the first chirp signal reflected by the target, and mixes the signal received by the receiving antenna 202 with the second chirp signal in even-numbered transmission periods to output a reflected wave signal resulting from the second chirp signal reflected by the target. Also, the second receiving sub-block (e.g., corresponding to the second receiving circuit) mixes the signal received by the receiving antenna 202 with the second chirp signal in odd-numbered transmission periods to output a reflected wave signal resulting from the second chirp signal reflected by the target, and mixes the signal received by the receiving antenna 202 with the first chirp signal in even-numbered transmission periods to output a reflected wave signal resulting from the first chirp signal reflected by the target.

[0558] Note that the chirp signals to be processed in each reception sub-block in odd-numbered and even-numbered transmission periods (for example, the switching destinations of the first and second switching units 216) may be reversed. In this way, the chirp signals to be processed in each reception sub-block may be alternately switched for each transmission period.

[0559] Each antenna system processing unit 201-z included in the q-th receiving sub-block q The signal processing unit 206 has an A / D conversion unit 207, a beat frequency analysis unit 208, an output switching unit 217, and a Doppler analysis unit 210. Here, when q=1, z1=any one of 1 to N3, and when q=2, z2=any one of N3+1 to Na.

[0560] The signal output from the LPF 205 (for example, a beat signal) is converted into discrete sample data by the A / D converter 207 in the signal processor 206, which is discretely sampled.

[0561] The beat frequency analysis unit 208 included in the first reception sub-block analyzes the transmission period T r For each time, N obtained in a given time range (range gate) data The discrete sample data are subjected to FFT processing. Here, the range gate is set to the frequency sweep time T sw Set (q). For example, q=1,2. When q=1, T sw (1) represents the frequency sweep time of the first chirp signal, and when q=2, T sw (2) represents the frequency sweep time of the second chirp signal. In the beat frequency analysis unit 208 included in the first reception sub-block, q may be set to 1 in odd-numbered transmission periods and 2 in even-numbered transmission periods. As a result, the signal processing unit 206 of the first reception sub-block outputs a frequency spectrum in which a peak appears at the beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave) for the first chirp signal in odd-numbered transmission periods and the second chirp signal in even-numbered transmission periods.

[0562] The beat frequency analysis unit 208 included in the second reception sub-block also analyzes the transmission period T r For each time, N obtained in a given time range (range gate) data The discrete sample data are subjected to FFT processing. Here, the range gate is set to the frequency sweep time T sw Set (q). For example, q=1,2. When q=1, T sw (1) represents the frequency sweep time of the first chirp signal, and when q=2, T sw (2) represents the frequency sweep time of the second chirp signal. In the beat frequency analysis unit 208 included in the second reception sub-block, q may be set to 2 in odd-numbered transmission periods and 1 in even-numbered transmission periods, for example. As a result, the signal processing unit 206 of the second reception sub-block outputs a frequency spectrum in which a peak appears at the beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave) relative to the second chirp signal in odd-numbered transmission periods and the first chirp signal in even-numbered transmission periods.

[0563] Here, the zth signal of the qth receiving sub-block obtained by the mth chirp pulse transmission is q The beat frequency response output from the beat frequency analysis unit 208 in the th signal processing unit 206 is referred to as "RFT zq (f b , m) where f b represents the beat frequency index, which corresponds to the FFT index (bin number). For example, f b =0,~,N data / 2-1, z1=1~N3, z2=N3+1~Na, m=1~2N C where q=1 or 2. The beat frequency index f b The smaller the beat frequency, the shorter the delay time of the reflected wave signal (for example, the closer the distance to the target).

[0564] For example, if m is odd, RFT z1 (f b , m) represents the frequency spectrum where a peak appears at the beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave) relative to the first chirp signal, and RFT z2 (f b , m) represents the frequency spectrum in which a peak appears at the beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave) relative to the second chirp signal. On the other hand, for example, if m is an even number, RFT z1 (f b , m) represents the frequency spectrum where a peak appears at the beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave) relative to the second chirp signal, and RFT z2 (f b , m) represents a frequency spectrum in which a peak appears at the beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave) relative to the first chirp signal.

[0565] The output switching unit 217 in the z1-th signal processing unit 206 of the first reception sub-block receives the beat frequency response RFT input from the beat frequency analysis unit 208. z1 (f b, m) is output to the first Doppler analysis unit 210 (or Doppler analysis unit 210-1) if m is an odd number, and is output to the second Doppler analysis unit 210 (or Doppler analysis unit 210-2) if m is an even number.

[0566] The output switching unit 217 in the z2-th signal processing unit 206 in the second reception sub-block receives the beat frequency response RFT input from the beat frequency analysis unit 208. z2 (f b , m) is output to the second Doppler analysis unit 210 if m is an odd number, and to the first Doppler analysis unit 210 if m is an even number.

[0567] As a result, one of the first Doppler analyzers 210 in each receiving sub-block processes the reflected wave signals for the first chirp signal received by the receiving antennas 202-1 to 202-N3 in odd-numbered transmission periods, and processes the reflected wave signals for the first chirp signal received by the receiving antennas 202-N3+1 to 202-Na in even-numbered transmission periods. Also, one of the second Doppler analyzers 210 in each receiving sub-block processes the reflected wave signals for the second chirp signal received by the receiving antennas 202-N3+1 to 202-Na in odd-numbered transmission periods, and processes the reflected wave signals for the second chirp signal received by the receiving antennas 202-1 to 202-N3 in even-numbered transmission periods.

[0568] Furthermore, for example, the first receiving sub-block processes reflected wave signals for the first chirp signal received by the receiving antennas 202-1 to 202-N3 in odd-numbered transmission periods, and processes reflected wave signals for the second chirp signal received by the receiving antennas 202-1 to 202-N3 in even-numbered transmission periods. Furthermore, for example, the second receiving sub-block processes reflected wave signals for the second chirp signal received by the receiving antennas 202-N3+1 to 202-Na in odd-numbered transmission periods, and processes reflected wave signals for the first chirp signal received by the receiving antennas 202-N3+1 to 202-Na in even-numbered transmission periods.

[0569] The first Doppler analyzer 210 in the z1-th signal processor 206 of the first receiving sub-block calculates the N C Beat frequency response RFT obtained by transmitting a single chirp pulse z1 (f b , 1), RFT z1 (f b , 3), ...using the distance index f b For example, the first Doppler analyzer 210 may estimate the Doppler frequency from a reflected wave signal of the first chirp signal reflected by a target.

[0570] Furthermore, the second Doppler analyzer 210 in the z1-th signal processor 206 of the first receiving sub-block calculates the N C Beat frequency response RFT obtained by transmitting a single chirp pulse z1 (f b , 2), RFT z1 (f b , 4), ...using the distance index f b For example, the second Doppler analyzer 210 may estimate the Doppler frequency from a reflected wave signal of the second chirp signal reflected by a target.

[0571] Furthermore, the first Doppler analyzer 210 in the z2-th signal processor 206 of the second receiving sub-block calculates the NC Beat frequency response RFT obtained by transmitting a single chirp pulse z2 (f b , 2), RFT z2 (f b , 4), ...using the distance index f b For example, the first Doppler analyzer 210 may estimate the Doppler frequency from a reflected wave signal of the first chirp signal reflected by a target.

[0572] Furthermore, the second Doppler analyzer 210 in the z2-th signal processor 206 of the second receiving sub-block calculates the N C Beat frequency response RFT obtained by transmitting a single chirp pulse z2 (f b , 1), RFT z2 (f b , 3), ...using the distance index f b For example, the second Doppler analyzer 210 may estimate the Doppler frequency from a reflected wave signal of the second chirp signal reflected by a target.

[0573] For example, N c If is a power of 2, FFT processing can be applied in Doppler analysis. In this case, the FFT size is N c The maximum Doppler frequency at which aliasing does not occur, derived from the sampling theorem, is ±1 / (4T r ) and the Doppler frequency index f s The Doppler frequency interval is 1 / (N c x2T r ) and the Doppler frequency index f s The range of f s = -N c / 2, ~, 0, ~, N c / 2-1.

[0574] In the following, as an example, c The case where N is a power of 2 will be explained. cIf is not a power of 2, for example, by including zero-padded data, FFT processing can be performed with a data size that is a power of 2. Furthermore, the Doppler analysis unit 210 may multiply by a window function coefficient such as a Han window or a Hamming window during FFT processing. Applying a window function can suppress side lobes that occur around the beat frequency peak.

[0575] For example, the output VFT of the first Doppler analyzer 210 in the z1-th signal processor 206 of the first receiving sub-block is z1,1 (f b , f s ), and the output VFT of the second Doppler analyzer 210 z1,2 (f b , f s ) are shown in the following equations (72) and (73), where j is the imaginary unit and z1=1 to N3.

number

number

[0576] Also, for example, the output VFT of the first Doppler analyzer 210 in the z2-th signal processor 206 of the second receiving sub-block z2,1 (f b , f s ), and the output VFT of the second Doppler analyzer 210 z2,2 (f b , f s ) are shown in the following equations (74) and (75). Note that j is an imaginary unit, and z2=N3+1 to Na.

number

number

[0577] The processing in each component of the signal processing unit 206 has been described above.

[0578] The CFAR unit 211 may include, for example, a first CFAR unit 211 (or CFAR unit 211-1) and a second CFAR unit 211 (or CFAR unit 211-2) corresponding to the first chirp signal and the second chirp signal having different center frequencies, respectively. Similarly, the Doppler demultiplexing unit 212 may include, for example, a first Doppler demultiplexing unit 212 (or Doppler demultiplexing unit 212-1) and a second Doppler demultiplexing unit 212 (or Doppler demultiplexing unit 212-2) corresponding to the first chirp signal and the second chirp signal having different center frequencies, respectively.

[0579] 19 shows a configuration in which CFAR units 211 are provided in parallel (CFAR units 211-1 and 211-2), but it is also possible to provide a single CFAR unit 211 and have its inputs switched over sequentially for processing. Also, while Fig. 19 shows a configuration in which Doppler demultiplexing units 212 are provided in parallel (Doppler demultiplexing units 212-1 and 212-2), it is also possible to provide a single Doppler demultiplexing unit 212 and have its inputs switched over sequentially for processing.

[0580] In FIG. 19, the CFAR unit 211 performs CFAR processing (for example, adaptive threshold determination) using the output from the Doppler analysis unit 210 of the signal processing unit 206 included in the first and second reception sub-blocks, and calculates the distance index f that gives a local peak signal. b_cfar and the Doppler frequency index f s_cfar Extract.

[0581] In FIG. 19, the CFAR unit 211 may include a first CFAR unit 211 (also referred to as CFAR unit 211-1) that performs CFAR processing using the output of the first Doppler analysis unit 210 of the signal processing unit 206 included in the first and second reception sub-blocks, and a second CFAR unit 211 (also referred to as CFAR unit 211-2) that performs CFAR processing using the output of the second Doppler analysis unit 210 of the signal processing unit 206 included in the first and second reception sub-blocks.

[0582] The first CFAR unit 211 performs CFAR processing (for example, adaptive threshold determination) using the output from the first Doppler analysis unit 210 of the signal processing unit 206 included in the first and second reception sub-blocks, which is the result of estimating the Doppler frequency from the reflected wave signal of the first chirp signal reflected by the target, and determines the distance index f that gives a local peak signal. b_cfar and the Doppler frequency index f s_cfar Extract.

[0583] The second CFAR unit 211 performs CFAR processing (for example, adaptive threshold determination) using the output from the second Doppler analysis unit 210 of the signal processing unit 206 included in the first and second reception sub-blocks, which is the result of estimating the Doppler frequency from the reflected wave signal of the second chirp signal reflected by the target, and calculates the distance index f b_cfar and the Doppler frequency index f s_cfar Extract.

[0584] The q-th CFAR unit 211 (q=1, 2) adds the power of the outputs of the q-th Doppler analyzers 210 of the signal processors 206 included in the first and second reception sub-blocks, for example, as shown in the following equation (76), and performs two-dimensional CFAR processing consisting of a distance axis and a Doppler frequency axis (corresponding to relative velocity), or CFAR processing that combines one-dimensional CFAR processing. For the two-dimensional CFAR processing or the CFAR processing that combines one-dimensional CFAR processing, the processing disclosed in Non-Patent Document 2, for example, may be applied. Here, z1=1 to N3, and z2=N3+1 to Na.

number

[0585] The qCFAR unit 211 adaptively sets a threshold value and calculates the distance index f th at which the received power is greater than the threshold value. b_cfar (q), the Doppler frequency index f s_cfar (q), and received power information PowerFT(f b_cfar (q), f s_cfar(q)) is output to the q-th Doppler demultiplexing unit 212.

[0586] The Doppler demultiplexing unit 212 may include a first Doppler demultiplexing unit 212 (also referred to as Doppler demultiplexing unit 212-1) that performs Doppler demultiplexing processing using the output of the first CFAR unit 211 and the output of the first Doppler analysis unit 210 of the signal processing unit 206 included in each receiving sub-block, and a second Doppler demultiplexing unit 212 (also referred to as Doppler demultiplexing unit 212-2) that performs Doppler demultiplexing processing using the output of the second CFAR unit 211 and the output of the second Doppler analysis unit 210-2 of the signal processing unit 206 included in each receiving sub-block.

[0587] The q-th Doppler demultiplexing unit 212 (q=1, 2) receives information (for example, a distance index f b_cfar (q), the Doppler frequency index f s_cfar (q), and received power information PowerFT(f b_cfar (q), f s_cfar Based on (q)), the output from the qth Doppler analysis unit 210 included in each receiving sub-block is used to separate the transmission signals (e.g., reflected wave signals for the transmission signals) transmitted from each transmitting antenna 106 from the Doppler multiplexed transmitted signals (hereinafter referred to as "Doppler multiplexed signals").

[0588] The q-th Doppler demultiplexing unit 212 outputs, for example, information about the separated signals to the Doppler determining unit 213 and the direction estimating unit 214. The information about the separated signals includes, for example, a distance index f b_cfar The separation index information of the first Doppler demultiplexing unit 212 is a Doppler frequency index obtained by separating the signals transmitted from the transmitting antennas Tx#1, Tx#2, to Tx#N1 included in the first transmission sub-block, and each of the indexes (f demul_Tx#1 , f demul_Tx#2 , ~, f demul_Tx#N1) Similarly, the separation index information of the second Doppler demultiplexing unit 212 is a Doppler frequency index obtained by separating the signals transmitted from the transmitting antennas Tx#N1+1, Tx#N1+2, to Tx#Nt included in the second transmission sub-block, and is represented by (f demul_Tx#N1+1 , f demul_Tx#N1+2 , ~, f demul_Tx#Nt ) is written as

[0589] The q-th Doppler demultiplexing unit 212 outputs the output from the q-th Doppler analysis unit 210 to the direction estimation unit 214. The q-th Doppler demultiplexing unit 212 uses information input from the q-th CFAR unit 211 (for example, the distance index f b_cfar (q), the Doppler frequency index f s_cfar (q), and received power information PowerFT(f b_cfar (q), f s_cfar Based on (q)), the output from the Doppler analyzer 210 included in the q-th reception sub-block may be output to the direction estimator 214.

[0590] An example of the operation of the q-th Doppler demultiplexing unit 212 will be described below together with the operation of the Doppler shift unit 105 in the radar transmitter 100b.

[0591] [How to set the Doppler shift amount] An example of a method for setting the amount of Doppler shift applied in the Doppler shifter 105 will be described.

[0592] In this embodiment, the input of the first chirp signal and the second chirp signal to the mixer unit 204 is switched between odd-numbered transmission cycles and even-numbered transmission cycles, and the same transmission phase change is imparted to these received signals. Therefore, this embodiment differs from the third embodiment in that the Doppler shift unit 105 imparts the same phase rotation to the chirp signal in odd-numbered transmission cycles and even-numbered transmission cycles. For example, in odd-numbered transmission cycles, the Doppler shift unit 105 imparts to the chirp signal a phase rotation that sets the same Doppler shift amount as in the third embodiment, and in even-numbered transmission cycles, the Doppler shift unit 105 imparts to the chirp signal a phase rotation that sets the same Doppler shift amount as in the third embodiment.

[0593] For example, the present embodiment differs from the equations (62) and (63) described in the third embodiment in the following respects.

[0594] The Doppler shift units 105-1 to 105-N1 of the first transmission sub-block perform a Doppler shift amount DOP that differs between the Doppler shift units 105 for the input odd-numbered m=2u−1-th first chirp signal. nsub1 The phase rotation φ as shown in the following equation (77) nsub1 (2u-1) is added to the Doppler-shifted signal, and the signal after the Doppler shift is output to the transmitting antenna 106 (for example, Tx#1 to Tx#N1), where nsub1=1 to N1 and u=1 to Nc.

number

[0595] Similarly to the odd-numbered signals, the Doppler shift units 105-1 to 105-N1 of the first transmission sub-block also apply different Doppler shift amounts DOP nsub1 The phase rotation φ as shown in the following equation (78) nsub1 (2u) is granted.

number

[0596] As a result, a different Doppler shift amount is imparted to the transmission signals transmitted from the plurality of transmission antennas 106 (for example, Tx#1 to Tx#N1) included in the first transmission sub-block in each transmission period. Also, the transmission signals transmitted from the transmission antennas 106 (for example, Tx#1 to Tx#N1) included in the first transmission sub-block are imparted with a different Doppler shift amount in each transmission period, for example, when the Doppler multiplexing number N DM =N1 and may be Doppler multiplexed.

[0597] Similarly, the Doppler shift units 105-N1+1 to 105-Nt of the second transmission sub-block perform Doppler shifts DOP that are different from each other among the Doppler shift units 105 for the input odd-numbered m=2u−1-th second chirp signal. nsub2 The phase rotation φ as shown in the following equation (79) nsub2 (m) is added, and the Doppler-shifted signal is output to the transmitting antenna 106 (for example, Tx#N1+1 to Tx#Nt), where nsub2=1 to N2 and u=1 to Nc.

number

[0598] Similarly to the odd-numbered signals, the Doppler shift units 105-N1+1 to 105-Nt of the second transmission sub-block apply different Doppler shift amounts DOP nsub2 The phase rotation φ as shown in the following equation (80) nsub2 (2u) is granted.

number

[0599] As a result, a different Doppler shift amount is imparted to the transmission signals transmitted from the plurality of transmission antennas 106 (for example, Tx#N1+1 to Tx#Nt) included in the second transmission sub-block in each transmission period. Also, the transmission signals transmitted from the transmission antennas 106 (for example, Tx#N1+1 to Tx#Nt) included in the second transmission sub-block are imparted with a different Doppler shift amount in each transmission period. DM =N2.

[0600] It should be noted that the present embodiment is not limited to the equations (62) and (63), and the setting of the amount of Doppler shift in the Doppler shifter 105 described in the third embodiment may be applied to the present embodiment.

[0601] For example, the radar device 10b may perform uneven Doppler multiplexing on the first chirp signal and the second chirp signal with Doppler multiplexing numbers N1 and N2, respectively. Alternatively, the radar device 10b may perform uneven Doppler multiplexing on at least one of the first chirp signal and the second chirp signal with Doppler multiplexing numbers N1 and N2, respectively.

[0602] [Example of operation of Doppler demultiplexing unit 212] The first Doppler demultiplexing unit 212 detects the Doppler shift amount DOP between the Doppler shift units 105-1 to 105-N1 (for example, between the transmission antennas 106-1 to 106-N1) included in the first transmission sub-block. nsub1 The Doppler shift intervals are not equal, but at least one of the Doppler intervals is set to be different, and the transmitted signals are separated and received.

[0603] The first Doppler demultiplexing unit 212 separates the signals that are Doppler multiplexed at uneven intervals based on the outputs of the first Doppler analysis unit 210 and the first CFAR unit 211 in the first and second reception sub-blocks. b_cfar (1), the distance index f b_cfarSeparation index information (f demul_Tx#1 , f demul_Tx#2 ,~ , f demul_Tx#N1 ) and outputs the output of the Doppler analysis unit 210 to the Doppler determination unit 213.

[0604] In this embodiment, the input of the first chirp signal and the second chirp signal to the mixer unit 204 is switched between odd-numbered transmission cycles and even-numbered transmission cycles, and the same transmission phase change is applied to these received signals. Therefore, the Doppler shift unit 105 applies the same phase rotation to odd-numbered transmission cycles and even-numbered transmission cycles. Correspondingly, the operation of the first Doppler demultiplexing unit 212 can be explained by replacing "Nt" with "N1" and adding "T" in the description of the operation of the Doppler shift unit 105 in the first embodiment. rs " to "2T r " can be used to separate signals Doppler multiplexed between transmitting antennas 106-1 to 106-N1. Therefore, detailed description of the operation of first Doppler demultiplexing section 212 will be omitted.

[0605] Similarly, the second Doppler demultiplexing unit 212 calculates the Doppler shift amount DOP between the Doppler shift units 105-N1+1 to 105-Nt (for example, between the transmitting antennas 106-N1+1 to 106-Nt) included in the second transmission sub-block. nsub2 The Doppler shift intervals are not equal, but at least one of the Doppler intervals is set to be different, and the transmitted signals are separated and received.

[0606] The second Doppler demultiplexing unit 212 separates the signals that are Doppler multiplexed at uneven intervals based on the outputs of the second Doppler analysis unit 210 and the second CFAR unit 211 in the first and second reception sub-blocks. b_cfar (2), the distance index f b_cfar Separation index information (fdemul_Tx#N1+1 , f demul_Tx#N1+2 ,~ , f demul_Tx#Nt ), and outputs the output of the Doppler analysis unit 210 to the Doppler determination unit 213.

[0607] In this embodiment, the input of either the first chirp signal or the second chirp signal to the mixer unit 204 is switched between odd-numbered transmission cycles and even-numbered transmission cycles, and the same transmission phase change is applied to these received signals. Therefore, the Doppler shift unit 105 applies the same phase rotation to odd-numbered transmission cycles and even-numbered transmission cycles. Correspondingly, the operation of the second Doppler demultiplexing unit 212 can be explained by replacing "Nt" with "N2" and adding "T" in the description of the operation of the Doppler shift unit 105 in the first embodiment. rs " to "2T r ", the signals Doppler multiplexed among the transmitting antennas 106-N1+1 to 106-Nt can be demultiplexed. Therefore, a detailed description of the operation of the second Doppler demultiplexing section 212 will be omitted.

[0608] [Example of operation of Doppler determination unit 213] 19, the Doppler determination unit 213 determines the Doppler frequency corresponding to the Doppler peak based on the outputs of the first Doppler demultiplexing unit 212 and the second Doppler demultiplexing unit 212. For example, the Doppler determination unit 213 determines the Doppler frequency f d_TargetDoppler is the Doppler frequency range -1 / (2T r ) ≦ f d_TargetDoppler <1 / (2T r ), the Doppler detection range can be further expanded by determining the Doppler frequency of the target.

[0609] For example, the Doppler determination unit 213 determines the distance index f b_cfar (1) and f b_cfar (2) is common to the separation index information (f demul_Tx#1 , f demul_Tx#2 ,~,f demul_Tx#N1) and separation index information (f demul_Tx#N1+1 , f demul_Tx#N1+2 ,~,f demul_Tx#Nt ) to the Doppler frequency range -1 / (2T r ) ≦ f d_TargetDoppler <1 / (2T r ) and determine the Doppler frequency of the target including the Doppler frequency exceeding the Doppler frequency of the target.

[0610] The Doppler frequency range in the Doppler determination unit 213 is −1 / (2T r ) ≦ f d_TargetDoppler <1 / (2T r ), the principle of determining the Doppler frequency of a target including a Doppler frequency exceeding 1 / 2 Hz is, as in the first embodiment, based on the fact that the center frequencies of the first chirp signal and the second chirp signal, which are radar transmission signals generated by the signal generation control unit 104 and the radar transmission signal generation unit 101, are different from each other.

[0611] In the first embodiment, the Doppler frequency is determined based on the change in Doppler frequency in the Doppler multiplexed signal for the same transmitting antenna 106. In contrast, in this embodiment, the Doppler determination unit 213 determines the Doppler frequency based on the change in Doppler frequency in the Doppler multiplexed signal for a different transmitting antenna 106. When a different transmitting antenna 106 is used, the reception phase changes, but the received Doppler frequency does not change. For this reason, as in the first embodiment, the Doppler determination unit 213 determines the Doppler frequency range -1 / (2T r ) ≦ f d_TargetDoppler <1 / (2T r ) can be used to determine the Doppler frequency of targets containing Doppler frequencies exceeding 100 kHz.

[0612] The operating principle of the Doppler frequency determination process and an example of the operation of Doppler determination unit 213 differ from the operating principle of the Doppler frequency determination process and an example of the operation of Doppler determination unit 213 described in embodiment 1 in the following points (1), (2), and (3). (1) "T rs " to "2Tr " and replace it with (2) In the first embodiment, the Doppler determination unit 213 determines the distance index f output from the first Doppler demultiplexing unit 212. b_cfar Separation index information (f demul_Tx#1 (1), f demul_Tx#2 (1),~,f demul_Tx#Nt Based on (1), the Doppler frequency of the target is within the Doppler frequency range -1 / (2T rs ) ≦f d_TargetDoppler <1 / (2T rs ) and the estimated Doppler frequency f d_VFT In contrast to this, in this embodiment, the Doppler determination unit 213 calculates the distance index f b_cfar Separation index information (f demul_Tx#1 , f demul_Tx#2 ,~,f demul_Tx#N1 ), the Doppler frequency of the target is in the Doppler frequency range -1 / (4T r ) ≦f d_TargetDoppler <1 / (4T r ) and the estimated Doppler frequency f d_VFT (1) is calculated, and (3) In the first embodiment, the Doppler determination unit 213 determines the distance index f output from the second Doppler demultiplexing unit 212. b_cfar (2) Separation index information of Doppler multiplexed signals (f demul_Tx#1 (2), f demul_Tx#2 (2),~,f demul_Tx#Nt (2)), the Doppler frequency of the target is within the Doppler frequency range -1 / (2T rs ) ≦f d_TargetDoppler <1 / (2T rs ) and the estimated Doppler frequency f d_VFT In contrast to this, in this embodiment, the Doppler determination unit 213 calculates the distance index f b_cfar (2) Separation index information ...

Claims

1. a transmission circuit that outputs, in each transmission period, a first transmission signal having a first center frequency and a second transmission signal having a second center frequency that is higher than the first center frequency; a transmitting antenna for transmitting the first transmission signal and the second transmission signal; a receiving antenna that receives a first reflected wave signal resulting from the first transmission signal being reflected by a target and a second reflected wave signal resulting from the second transmission signal being reflected by the target; a receiving circuit including: a first Doppler analysis circuit that estimates a first Doppler frequency from the first reflected wave signal; a second Doppler analysis circuit that estimates a second Doppler frequency from the second reflected wave signal; and a determination circuit that determines the number of times that the first Doppler frequency and the second Doppler frequency are folded back; Equipped with the second center frequency is a frequency higher than (1+1 / Nc) times the first center frequency (Nc is an integer indicating the number of times that each of the first transmission signal and the second transmission signal is transmitted per transmission period within a predetermined period), The determination circuit estimating a first peak position of the first Doppler frequency observed by the first reflected wave signal; estimating a second peak position of the second Doppler frequency based on the first peak position and a ratio between the first center frequency and the second center frequency; determining the number of times the Doppler frequency of the target has folded back based on the degree of coincidence between the second peak position and a third peak position observed in the second reflected wave signal; Radar equipment.

2. the second center frequency is lower than 1.25 times the first center frequency; The radar device according to claim 1 .

3. the second center frequency is lower than 7 / 6 times the first center frequency; The radar device according to claim 1 .

4. the transmitting antenna alternately transmits the first transmission signal and the second transmission signal for each transmission period; The radar device according to claim 1 .

5. the transmitting antenna simultaneously transmits the first transmission signal and the second transmission signal for each transmission period; The radar device according to claim 1 .

6. the transmitting antenna is a plurality of transmitting antennas; Among the plurality of transmitting antennas, the number of transmitting antennas that transmit the first transmission signals and the number of transmitting antennas that transmit the second transmission signals are the same or different by one. The radar device according to claim 5 .

7. the transmitting antenna is a plurality of transmitting antennas; the transmission circuit imparts, to at least one of the first transmission signal and the second transmission signal transmitted from the plurality of transmission antennas, Doppler shift amounts at intervals obtained by dividing, at unequal intervals, a Doppler frequency range that is a target for determining the number of times the Doppler frequency is folded back; The radar device according to claim 1 .

8. The intervals between the Doppler shift amounts divided into the unequal intervals are [Equation 1] where Nt is an integer indicating the number of the plurality of transmitting antennas, δ is an integer equal to or greater than 1, and T rs is a transmission period in which the set of the first transmission signal and the second transmission signal is transmitted), The second center frequency is a frequency [Equation 2] is a higher frequency than The radar device according to claim 7.

9. the target is a plurality of targets; the first reflected wave signal is a plurality of first reflected wave signals, the second reflected wave signal is a plurality of second reflected wave signals, the first Doppler analysis circuit estimates the first Doppler frequency from the plurality of first reflected wave signals; the second Doppler analysis circuit estimates the second Doppler frequency from the plurality of second reflected wave signals; the receiving circuit further includes a direction estimation circuit, of the first Doppler analysis circuit and the second Doppler analysis circuit, that performs direction estimation based on a Doppler frequency estimated by the Doppler analysis circuit that separates the first reflected wave signal and the second reflected wave signal. The radar device according to claim 8.

10. The receiving antenna includes a first receiving antenna and a second receiving antenna; the first Doppler analysis circuit processes the first reflected wave signal received by the first receiving antenna in either an even-numbered or odd-numbered transmission period, and processes the first reflected wave signal received by the second receiving antenna in the other of either an even-numbered or odd-numbered transmission period; the second Doppler analysis circuit processes the second reflected wave signal received by the second receiving antenna in the one transmission period, and processes the second reflected wave signal received by the first receiving antenna in the other transmission period. The radar device according to claim 5 .

11. The receiving antenna includes a first receiving antenna and a second receiving antenna; The receiving circuit a first receiving circuit that mixes a signal received by the first receiving antenna with the first transmission signal every first period to output the first reflected wave signal, and that mixes a signal received by the first receiving antenna with the second transmission signal every second period different from the first period to output the second reflected wave signal; a second receiving circuit that mixes the signal received by the second receiving antenna with the second transmission signal every first period to output the second reflected wave signal, and that mixes the signal received by the second receiving antenna with the first transmission signal every second period to output the first reflected wave signal. The radar device according to claim 5 .

12. the first transmission signal and the second transmission signal are chirp signals; The chirp signal of the first center frequency and the chirp signal of the second center frequency have the same frequency sweep bandwidth. The radar device according to claim 1 .

13. The chirp signal of the first center frequency and the chirp signal of the second center frequency have different frequency sweep times. The radar device according to claim 12.

14. The receiving antenna is a first receiving antenna that receives the first reflected wave signal that is the first transmitted signal reflected by the target; a second receiving antenna that receives the second reflected wave signal that is the second transmitted signal reflected by the target, the receiving circuit includes a first receiving circuit that processes the first reflected wave signal and a second receiving circuit that processes the second reflected wave signal; the transmission circuit includes a first transmission circuit that outputs the first transmission signal and a second transmission circuit that outputs the second transmission signal; the transmitting antennas include a first transmitting antenna that transmits the first transmission signal and a second transmitting antenna that transmits the second transmission signal; the first transmitting antenna, the first transmitting circuit, the first receiving antenna, and the first receiving circuit are included in a first chip; the second transmitting antenna, the second transmitting circuit, the second receiving antenna, and the second receiving circuit are included in a second chip; The radar device according to claim 5 .

15. The receiving antenna is a first receiving antenna that receives the first reflected wave signal resulting from the first transmission signal being reflected by the target and the second reflected wave signal resulting from the second transmission signal being reflected by the target; a second receiving antenna that receives the first reflected wave signal and the second reflected wave signal, The receiving circuit a first receiving circuit that processes the first reflected wave signal received by the first receiving antenna in either an even-numbered or odd-numbered transmission period, and processes the second reflected wave signal received by the first receiving antenna in the other of the even-numbered or odd-numbered transmission periods; a second receiving circuit that processes the second reflected wave signal received by the second receiving antenna in the one transmission period and processes the first reflected wave signal received by the second receiving antenna in the other transmission period; Including, the transmission circuit includes a first transmission circuit that outputs the first transmission signal and a second transmission circuit that outputs the second transmission signal; the transmitting antennas include a first transmitting antenna that transmits the first transmission signal and a second transmitting antenna that transmits the second transmission signal; the first transmitting antenna, the first transmitting circuit, the first receiving antenna, and the first receiving circuit are included in a first chip; the second transmitting antenna, the second transmitting circuit, the second receiving antenna, and the second receiving circuit are included in a second chip; The radar device according to claim 5 .

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