Radar device

Abstract

This radar device is provided with: a plurality of transmission antennas including a first transmission antenna that forms a first beam and a second transmission antenna that forms a second beam different from the first beam; and a transmission circuit that multiplexes and transmits, from the plurality of transmission antennas, a transmission signal to which a phase rotation corresponding to each of the Doppler shift amounts allocated to each of the plurality of transmission antennas has been applied, and that is non-equally spaced on the Doppler frequency axis on the basis of the Doppler shift intervals of the plurality of transmission antennas. A first pattern of the Doppler shift amount allocated to the first transmission antenna is different from a second pattern of the Doppler shift amount allocated to the second transmission antenna.

Description

Technical Field

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

[0002] In recent years, research has been progressing on radar devices that use short-wavelength radars including microwaves or millimeter waves that can achieve high resolution to transmit signals. In addition, in order to improve safety when outdoors, it is required to develop radar devices that can detect not only vehicles but also small objects such as pedestrians within a wide angle range (for example, so-called wide-angle radar devices).

[0003] As a structure of a radar device with a wide-angle detection range, for example, there is a structure using the following method (arrival angle estimation method. Direction of Arrival (DOA) estimation), which receives the reflected wave from the target through an array antenna composed of multiple antennas (or also called antenna elements), and estimates the direction of arrival (also called arrival angle) of the reflected wave from the target based on the reception phase difference with respect to the element spacing (antenna spacing). For example, as an arrival angle estimation method, the Fourier method can be listed, or, as a method that can obtain high resolution, the Capon method, MUSIC (Multiple Signal Classification) and ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques, signal parameter estimation based on rotational invariance techniques) can be listed.

[0004] In addition, as a radar device, for example, the following structure has been proposed (sometimes also called "MIMO (Multiple Input Multiple Output) radar"): in addition to the receiving part, the transmitting part also has multiple antennas (array antennas), and beam scanning is performed by signal processing using the transmitting and receiving array antenna (for example, refer to non-patent document 1).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2019-211388

[0008] Patent Document 2: U.S. Patent Publication No. 2022 / 0066012

[0009] Patent Document 3: Japanese Patent Application Publication No. 2008-304417

[0010] Patent Document 4: Japanese Patent Application No. 2011-526371

[0011] Patent Document 5: Japanese Patent Application Publication No. 2014-119344

[0012] Patent Document 6: Japanese Patent Application Publication No. 2019-052952

[0013] Patent Document 7: Japanese Patent Application Publication No. 2020-148754

[0014] Non-patent literature

[0015] 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

[0016] Non-patent document 2: M. Kronauge, H. Rohling, "Fast two-dimensional CFAR procedure", IEEE Trans. Aerosp. Electron. Syst., 2013, 49, (3), pp. 1817-1823

[0017] Non-patent literature 3: Direction-of-arrival estimation using signal subspacemodeling Cadzow, JA; Aerospace and Electronic Systems, IEEE Transactions on Volume: 28, Issue: 1 Publication Year: 1992, Page (s): 64-79 Summary of the invention

[0018] However, a method for detecting a target (or object) using a radar device (eg, MIMO radar) has not been fully studied.

[0019] The non-limiting embodiments of the present disclosure help provide a radar device that improves the detection accuracy of a target object.

[0020] A radar device according to an embodiment of the present disclosure includes: a plurality of transmitting antennas, including a first transmitting antenna forming a first beam and a second transmitting antenna forming a second beam different from the first beam; and a transmitting circuit for multiplexing and transmitting, from the plurality of transmitting antennas, transmitting signals to which phase rotations corresponding to Doppler frequency shift amounts respectively allocated to the plurality of transmitting antennas are assigned, wherein a first pattern of Doppler frequency shift amounts allocated to the first transmitting antenna is different from a second pattern of Doppler frequency shift amounts allocated to the second transmitting antenna based on the fact that Doppler frequency shift intervals of the plurality of transmitting antennas are unequally spaced on a Doppler frequency axis.

[0021] In addition, these broad or specific embodiments may be implemented by systems, devices, methods, integrated circuits, computer programs or recording media, or by any combination of systems, devices, methods, integrated circuits, computer programs and recording media.

[0022] According to an embodiment of the present disclosure, the detection accuracy of a target object of a radar device can be improved.

[0023] Further advantages and effects in one embodiment of the present disclosure will be clearly presented by the description and the drawings. The above advantages and / or effects are provided by several embodiments and the features described in the description and the drawings, but not necessarily all of them are provided in order to obtain one or more of the same features. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a diagram showing an example of time division multiplexing (TDM: Time Division Multiplexing) transmission.

[0025] Figure 2 This is a diagram showing an example of Doppler Division Multiplexing (DDM) transmission.

[0026] Figure 3 This is a diagram showing an example of unequal-interval Doppler multiplexing transmission.

[0027] Figure 4 This is a diagram showing an example of a multi-beam transmission MIMO radar.

[0028] Figure 5 This is a diagram showing an example of Doppler multiplexing transmission of a multi-beam transmission MIMO radar.

[0029] Figure 6 This is a diagram showing an example of Doppler multiplexing transmission of a multi-beam transmission MIMO radar.

[0030] Figure 7 This is a block diagram showing a configuration example of a radar device.

[0031] Figure 8 This is a diagram showing an example of a transmission signal when a chirp signal is used.

[0032] Fig. 9 This is a diagram showing an example of a chirp signal.

[0033] Fig.10 This is a diagram showing an example of a transmission signal and a reception signal when a chirp signal is used.

[0034] Fig.11 It is a diagram showing an example of setting the Doppler shift amount.

[0035] Fig.12 This is a diagram showing an example of a reception signal transmitted by Doppler multiplexing.

[0036] Fig.13 This is a diagram showing an example of a multi-beam transmission MIMO radar.

[0037] Fig.14 It is a diagram showing an example of setting the Doppler shift amount.

[0038] Fig.15 This is a diagram showing an example of a reception signal transmitted by Doppler multiplexing.

[0039] Fig.16 It is a diagram showing an example of setting the Doppler shift amount.

[0040] Fig.17 It is a diagram showing an example of setting the Doppler shift amount.

[0041] Fig.18 This is a flowchart showing an example of the demultiplexing operation of a Doppler multiplexed signal.

[0042] Fig.19 It is a diagram showing a configuration example of a transmitting antenna.

[0043] Fig. 20 This is a diagram showing an example of a multi-beam transmission MIMO radar.

[0044] Fig.21 This is a diagram showing an example of a MIMO antenna arrangement and a virtual receiving antenna arrangement.

[0045] Fig. 22 This is a diagram showing an example of a MIMO antenna arrangement and a virtual receiving antenna arrangement.

[0046] Fig.23 This is a diagram showing an example of a MIMO antenna arrangement and a virtual receiving antenna arrangement.

[0047] Fig.24This is a diagram showing an example of a multi-beam transmission MIMO radar.

[0048] Fig.25 This is a diagram showing an example of MIMO antenna configuration.

[0049] Fig.26 It is a diagram showing an example of setting the Doppler shift amount.

[0050] Fig. 27 It is a diagram showing an example of setting the Doppler shift amount.

[0051] Fig.28 It is a diagram showing an example of setting the Doppler shift amount.

[0052] Fig.29 This is a diagram showing an example of a multi-beam transmission MIMO radar.

[0053] Fig.30 This is a diagram showing an example of a multi-beam transmission MIMO radar.

[0054] Fig.31 This is a diagram showing an example of a multi-beam transmission MIMO radar.

[0055] Fig.32 This is a diagram showing an example of a multi-beam transmission MIMO radar.

[0056] Fig.33 This is a diagram showing an example of a multi-beam transmission MIMO radar. DETAILED DESCRIPTION

[0057] For example, MIMO radar transmits signals (radar transmission waves) multiplexed by time division, frequency division or code division from multiple transmission antennas (or, called "transmission array antennas"), receives signals (radar reflection waves) reflected by surrounding objects using multiple receiving antennas (or, called "receiving array antennas"), and demultiplexes and receives the multiplexed transmission signals from each received signal. Through this processing, MIMO radar can obtain the propagation path response represented by the product of the number of transmission antennas and the number of receiving antennas, and perform array signal processing on these received signals as a virtual receiving array. In addition, in MIMO radar, by appropriately configuring the element spacing in the transmission and reception array antenna, the antenna aperture of the virtual receiving array can be expanded and the angular resolution can be improved.

[0058] [About Multibeam Radar]

[0059] In order to improve the angle measurement performance such as angle measurement accuracy or angle resolution, it is preferable that the directional characteristics (or simply referred to as "directivity") of the multiple transmitting antennas or receiving antennas constituting the MIMO radar are the same. On the other hand, the directional characteristics of the transmitting antenna or the receiving antenna are set according to the detection distance or the detection angle range required by the radar. Therefore, if the transmitting antenna or the receiving antenna has only one directional characteristic, it may be difficult to meet the required specifications.

[0060] For example, in order to meet the required detection distance while satisfying a wide-angle detection angle range, there may be a situation where transmitting antennas or receiving antennas with multiple directional characteristics with different main beam directions (hereinafter sometimes referred to as "beam directions", "transmitting beam directions" or "receiving beam directions").

[0061] In addition, there may be a situation where, for example, the required detection distances for each detection angle direction are greatly different, and a situation where multiple transmitting antennas or receiving antennas with different directional characteristics in at least one of the beam direction and beam width suitable for each angle direction are used.

[0062] In addition, there may be situations where, for example, the detection angle ranges of multiple detection distances (for example, long-distance range, medium-distance range, and short-distance range) are greatly different, or where transmitting antennas or receiving antennas with multiple directional characteristics having approximately the same beam direction but different beam widths (for example, 3dB beam width or 6dB beam width) depending on the detection distance are used.

[0063] For example, when the number of transmitting antennas or receiving antennas is limited due to size or cost constraints of a radar device, using transmitting antennas or receiving antennas with different directional characteristics is an effective means of satisfying the required specifications.

[0064] In such a case, it is expected that a MIMO radar is constructed using a plurality of transmitting antennas or receiving antennas having different directional characteristics.

[0065] Examples of different directional characteristics of a transmitting antenna or a receiving antenna include a directional characteristic with the same beam width but different beam directions, a directional characteristic with different beam directions and beam widths, and a directional characteristic with the same beam direction but different beam widths.

[0066] Hereinafter, a MIMO radar using a plurality of transmitting antennas having different directional characteristics as described above (for example, transmitting antennas forming different beams) is referred to as a "multi-beam transmitting MIMO radar". Here, the multi-beam transmitting MIMO radar includes a plurality of transmitting antennas having different directional characteristics. In addition, the multi-beam transmitting MIMO radar may also be a structure including one or more transmitting antennas having the same directivity.

[0067] In addition, hereinafter, a MIMO radar using a plurality of receiving antennas having different directional characteristics as described above (for example, receiving antennas forming different beams) is referred to as a "multi-beam receiving MIMO radar". Here, the multi-beam receiving MIMO radar includes a plurality of receiving antennas having different directional characteristics. In addition, the multi-beam receiving MIMO radar may also be a structure including one or more receiving antennas with the same directivity.

[0068] Similarly, hereinafter, a MIMO radar using a plurality of transmitting antennas and receiving antennas having different directional characteristics as described above will be referred to as a "multi-beam transmitting / receiving MIMO radar" (or, multi-beam MIMO radar).

[0069] For example, Patent Document 1 discloses a 3-transmit MIMO radar structure in which two transmit antennas of a certain directivity and one transmit antenna of a different directivity are switched in a time division manner. In addition, Patent Document 1 discloses a structure in which a time period of code multiplexing transmission of two transmit antennas of a certain directivity and a time period of code multiplexing transmission of two transmit antennas of different directivity are switched.

[0070] In addition, for example, Patent Document 2 discloses a MIMO radar structure in which time division multiplexing and Doppler multiplexing are combined and switched between a directional transmission antenna for long distances and a directional transmission antenna for medium and short distances.

[0071] Hereinafter, attention will be paid to a multiplexing transmission method in a multi-beam transmission MIMO radar using a plurality of transmission antennas having different directional characteristics (for example, a plurality of transmission antennas forming different beams).

[0072] [About time division multiplexing transmission]

[0073] For example, as a multiplexing transmission method of MIMO radar using multiple transmission antennas, time division multiplexing (TDM) can be cited, which transmits signals by staggering the transmission time for each transmission antenna. Compared with frequency division multiplexing (FDM) and code division multiplexing (CDM), time division multiplexing can be implemented with a simpler structure, and by sufficiently expanding the transmission time interval, the orthogonality between the transmission signals can be well maintained.

[0074] For example, the MIMO radar using time division multiplexing transmission disclosed in Patent Document 3 sequentially switches the transmission antenna that transmits the transmission signal (e.g., transmission pulse or radar transmission wave) at a predetermined period, while outputting the transmission pulse as an example of the transmission signal. The MIMO radar using time division multiplexing transmission receives the signal obtained by the transmission pulse being reflected by an object using multiple receiving antennas, and after performing correlation processing between the received signal and the transmission pulse, performs, for example, spatial FFT (Fast Fourier Transform) processing (arrival direction estimation processing of the reflected wave).

[0075] In a MIMO radar using time division multiplexing transmission, a predetermined transmission time (or transmission interval) is pre-assigned to each of the multiple transmission antennas. Therefore, a multi-beam transmission MIMO radar using time division multiplexing transmission receives reflections from a target object according to the transmission time assigned to each of the multiple transmission antennas with different directivities in beam directions, thereby demultiplexing and receiving the reflected waves from the target object corresponding to the transmission signals of each of the transmission antennas in different beam directions.

[0076] Since the MIMO radar using time division multiplexing transmission sequentially switches the transmission antennas that transmit radar transmission waves at predetermined intervals, the time until transmission from all transmission antennas is completed tends to be longer than when frequency division multiplexing transmission or code division multiplexing transmission is used. Therefore, in the MIMO radar using time division multiplexing transmission, when multiple radar transmission waves are transmitted from each transmission antenna and Doppler frequency detection (for example, relative speed detection) is performed based on the received phase change of these transmission waves (for example, Patent Document 4). Figure 4 ), when Fourier frequency analysis is applied to detect Doppler frequency (for example, relative speed detection), the time interval for observing the reception phase change will be long. If the time interval for observing the reception phase change when Fourier frequency analysis is applied is long, it is easy to cause the maximum detectable Doppler frequency based on the sampling theorem to decrease, and the detectable Doppler frequency range (for example, relative speed range) to become smaller.

[0077] The following MIMO radar using time division multiplexing transmission is described. In this radar, for example, Figure 1 As shown, the transmission pulses are outputted while the transmission antennas (for example, Tx#1 and Tx#2) that transmit the chirp signal as the transmission radar wave are sequentially switched at the transmission cycle Tr.

[0078] For example, when there are Nt transmitting antennas ( Figure 1 In the case of Nt=2), the transmission time until the radar transmission wave from the Nt transmitting antennas is completed is Tr×Nt( Figure 1In the case of , it is 2Tr). In a MIMO radar using time division multiplexing transmission, if such time division multiplexing transmission is repeated Nc times and Fourier frequency analysis is applied to perform Doppler frequency detection (for example, relative speed detection), then according to the sampling theorem, the Doppler frequency range in which the Doppler frequency can be detected without aliasing is ±1 / (2Tr×Nt). Therefore, the larger the number of transmitting antennas Nt, the smaller the Doppler frequency range in which the Doppler frequency can be detected without aliasing. In addition, in a MIMO radar using time division multiplexing transmission, when a Doppler frequency is received that exceeds the range in which the Doppler frequency can be detected without aliasing, it is difficult to uniquely determine the Doppler frequency (for example, relative speed), and ambiguity is likely to occur.

[0079] For example, in a multi-beam MIMO radar using time division multiplexing transmission as in Patent Document 1, similarly to the MIMO radar using time division multiplexing transmission described above, the greater the number of transmitting antennas Nt, the smaller the Doppler frequency range in which the Doppler frequency can be detected without aliasing.

[0080] In the above, an example of time division multiplexing transmission has been described.

[0081] Next, as an example, attention will be paid to a method of multiplexing transmission signals and transmitting them simultaneously from a plurality of transmission antennas.

[0082] [About Doppler multiplexing transmission]

[0083] As a method of multiplexing and sending transmission signals simultaneously from multiple transmission antennas, there is, for example, a method of sending signals in a manner that allows a plurality of transmission signals in the Doppler frequency domain to be demultiplexed in a receiving unit (hereinafter referred to as "Doppler Division Multiplexing (DDM) transmission") (for example, refer to Patent Document 5).

[0084] In Doppler multiplexing transmission, the transmitting unit, for example, gives phase rotations that bring different Doppler frequency shift amounts to the transmitted signals according to the transmitting antennas, and transmits the transmitted signals from multiple transmitting antennas simultaneously. In Doppler multiplexing transmission, the signals received by multiple receiving antennas (reflected waves from the target object) are filtered in the Doppler frequency domain, so that the transmitted signals sent from each transmitting antenna are demultiplexed and received.

[0085] In a MIMO radar using Doppler multiplexing transmission, for example, a predetermined Doppler frequency domain (or Doppler frequency shift amount) is pre-assigned to each of a plurality of transmission antennas. For example, a multi-beam transmission MIMO radar using Doppler multiplexing transmission receives reflections from a target object according to the Doppler frequency domains to which transmission antennas in a plurality of different beam directions are respectively assigned, thereby demultiplexing and receiving the reflected waves from the target object corresponding to the transmission signals of the transmission antennas in a plurality of different beam directions.

[0086] In a MIMO radar using Doppler multiplexing transmission, transmission signals are transmitted simultaneously from a plurality of transmission antennas, thereby making it possible to shorten the time interval for observing the reception phase change when detecting the Doppler frequency (e.g., relative speed detection) by applying Fourier frequency analysis, compared to time division multiplexing transmission. On the other hand, in a MIMO radar using Doppler multiplexing transmission, the transmission signals of each transmission antenna are demultiplexed by filtering on the Doppler frequency axis, so that the effective Doppler frequency bandwidth averaged to each transmission signal is limited.

[0087] The following MIMO radar using Doppler multiplexing transmission is described. In this radar, for example, Figure 2 As shown in (a) of FIG. 1 , the transmission of a chirp signal output as a transmission radar wave with a transmission period Tr is repeated Nc times, and Doppler frequency detection (for example, relative speed detection) is performed by applying Fourier frequency analysis.

[0088] For example, in Figure 2 In (b), according to the sampling theorem, the Doppler frequency range that can detect the Doppler frequency without aliasing on the Doppler frequency axis is ±1 / (2Tr), which is expanded to Nt times (in Figure 2 In the case of Nt=2). On the other hand, in a MIMO radar using Doppler multiplexing transmission, since the transmission signal is demultiplexed by filtering on the Doppler frequency axis, the effective Doppler frequency range averaged per transmission signal is smaller than the Doppler frequency range ±1 / (2Tr). For example, when Tx#1 and Tx#2 are each assigned a Doppler frequency range of ±1 / (2Tr) that is equally divided into Nt ( Figure 2 In the case of Nt=2), when the Doppler shift (hereinafter also referred to as "Doppler shift amount" or "transmission Doppler shift amount") is 0 [Hz] and -1 / (2Tr) [Hz], the MIMO radar using Doppler multiplexing transmission multiplies the chirp signal (cp(t)) as the transmission signal by a phase rotation Φ1(n)=(n-1)ΔΦ1, Φ2(n)=(n-1)ΔΦ2 (where ΔΦ1=0, ΔΦ2=π) for each transmission period Tr. Here, n=1, 2, 3, 4, ..., and n is an index indicating the number of times the chirp signal is transmitted.

[0089] In this case, if Figure 2 As shown in (b), Doppler frequency domains are pre-allocated to multiple transmitting antennas Tx#1 and Tx#2. For example, -1 / (4Tr)≦fd1<1 / (4Tr) is allocated to the region of Doppler frequency fd1 of Tx#1 (for example, also called "Doppler division region"), and -1 / (2Tr)≦fd2<-1 / (4Tr) and 1 / (4Tr)≦fd2<1 / (2Tr) are allocated to the region of Doppler frequency fd2 of Tx#2.

[0090] MIMO radar using Doppler multiplexing transmission, for example, receives the signal from each transmission antenna reflected by the target object, performs filtering on the Doppler frequency axis, and thus demultiplexes the transmission signal and receives it. Figure 2 In (b), the MIMO radar using Doppler multiplexing transmission filters and extracts the signal obtained by the transmission signal from the transmission antenna Tx#1 reflected at the target object in the range of -1 / (4Tr)≦fd1<1 / (4Tr) on the Doppler frequency axis, thereby demultiplexing and receiving. Similarly, the MIMO radar using Doppler multiplexing transmission filters and extracts the signal obtained by the transmission signal from the transmission antenna Tx#2 reflected at the target object in the range of -1 / (2Tr)≦fd2<-1 / (4Tr) and 1 / (4Tr)≦fd2<1 / (2Tr) on the Doppler frequency axis, thereby demultiplexing and receiving.

[0091] Thus, in the MIMO radar using Doppler multiplexing transmission, the reception process is performed assuming that the reflected wave signals corresponding to the transmission signals from each transmission antenna are respectively included in the Doppler frequency range of ±1 / (2Tr×Nt), so the Doppler frequency range becomes the same as that when time division multiplexing transmission is performed. For example, in the MIMO radar using Doppler multiplexing transmission, the larger the number of transmission antennas Nt, the smaller the Doppler frequency range that can detect the Doppler frequency without aliasing.

[0092] In addition, in a multi-beam transmission MIMO radar using Doppler multiplexing transmission, similarly to the above-mentioned MIMO radar using Doppler multiplexing transmission, as the number of transmitting antennas Nt increases, the Doppler frequency range in which the Doppler frequency can be detected without aliasing tends to become smaller.

[0093] [About unequally spaced Doppler multiplexing transmission]

[0094] In the above-mentioned time division multiplexing transmission or Doppler multiplexing transmission, the reflected waves corresponding to the transmission signals from multiple transmitting antennas can be demultiplexed using the allocated transmission time or Doppler frequency domain. On the other hand, in time division multiplexing transmission and Doppler multiplexing transmission, if the number of transmitting antennas increases, the detection range of the Doppler frequency tends to become smaller. For example, in time division multiplexing and Doppler division multiplexing, the detectable Doppler frequency range is -1 / (2Nt×Tr)≦fd<1 / (2Nt×Tr), and the detection range of the Doppler frequency decreases inversely proportional to the number of transmitting antennas. Here, Nt is the number of transmitting antennas.

[0095] For example, Patent Document 6 discloses a method for expanding the detection range of Doppler frequency in Doppler multiplexing transmission. Patent Document 6 (for example, Figure 8 ) discloses the following method. For example, in the Doppler frequency shift amounts (or Doppler frequency domain) obtained by equally dividing the Doppler frequency range ±1(2Tr) capable of detecting the Doppler frequency without aliasing into (Nt+1), Nt Doppler frequency shift amounts are allocated to Nt transmission signals, and the transmission signals are simultaneously transmitted from Nt transmission antennas.

[0096] In such Doppler multiplexing transmission, a part of the Doppler frequency shift amounts that are equally divided into (Nt+1) is not allocated to the transmission signal. Therefore, in the Doppler frequency domain, each interval of the Doppler frequency shift amount assigned to the transmission signal subjected to Doppler multiplexing (hereinafter also referred to as "Doppler multiplexing interval" or "Doppler frequency shift interval") is unequally spaced. Hereinafter, this type of Doppler multiplexing transmission is referred to as "unequally spaced Doppler multiplexing transmission (unequally spaced DDM transmission)".

[0097] Figure 3 The following is an example of allocating Doppler multiplexed signals using unequally spaced Doppler multiplexing transmission when a radar transmission wave (e.g., a chirp signal) is transmitted at each transmission period Tr, using Nt=2 transmitting antennas and setting the unit of the Doppler frequency shift interval to Δfd=1 / (3Tr).

[0098] exist Figure 3, the transmission Doppler shift amounts assigned to the transmission antennas Tx#1 and Tx#2 are Δfd1=0 and Δfd2=1 / (3Tr)[Hz], respectively. For example, in order to assign the transmission Doppler shift amount Δfd1 to the transmission antenna Tx#1 in each n-th transmission cycle, a phase rotation Φ1(n)=ΔΦ1×(n-1) is assigned to the radar transmission wave (chirp signal). Similarly, for example, in order to assign the transmission Doppler shift amount Δfd2 to the transmission antenna Tx#2 in each n-th transmission cycle, a phase rotation Φ2(n)=ΔΦ2×(n-1) is assigned to the radar transmission wave (chirp signal). In addition, no transmission antenna is assigned to the Doppler shift amount Δfd3 corresponding to the phase rotation Φ3(n)=ΔΦ3×(n-1).

[0099] Here, Figure 3 It represents the transmission Doppler frequency allocated to the transmission antennas Tx#1 and Tx#2 when Δfd1=0, Δfd2=1 / (3Tr), ΔΦ1=0, ΔΦ2=2π×Δfd×Tr=2π / 3. Figure 3 In the example, the transmission Doppler frequency when Δfd3 = 2 / (3Tr) and ΔΦ3 = 2π × 2Δfd × Tr = 4π / 3 (or -2π / 3) is indicated by the “×” mark. Figure 3 As shown, no transmission antenna is allocated for the Doppler frequency shift amount Δfd3.

[0100] In addition, the phase rotation Φ n It can also be expressed as -π≦ΔΦ n <π. For example, it can be expressed as ΔΦ3=-2π / 3. The same is true below.

[0101] For example, consider Figure 3 As shown in FIG. 1 , the Doppler frequency shift interval between Tx#1 and Tx#2 is Δfd=1 / (3Tr), and the range (region) of observable Doppler frequencies is -1 / (2Tr)≦fd<1 / (2Tr), and includes Doppler frequencies outside this range. For example, when the received Doppler frequency of the Doppler multiplexed signal of Tx#1 or Tx#2 exceeds 1 / (2Tr), or is less than -1 / (2Tr), as shown in FIG. Figure 3 As shown, the Doppler frequency shift interval for Tx#1 and Tx#2 is Δf alias =1 / Tr-Δfd=2 / 3Tr. In the following, when “Doppler multiplexing interval” or “Doppler frequency shift interval” is described, in addition to Δfd, Δf alias .

[0102] Next, an example of demultiplexing reception processing of Doppler multiplexed signals in the case of using unequal-interval Doppler multiplexing transmission will be described.

[0103] In the demultiplexing reception process of the Doppler multiplexed signal when the non-uniformly spaced Doppler multiplexed transmission is used, for example, the following properties are used to detect the Doppler frequency (for example, relative speed detection) of the received signal of the radar reflected wave.

[0104] For example, in the output to which Fourier frequency analysis is applied, among the Doppler frequency shift amounts equally divided into Nt+1, the received power level of the Doppler frequency corresponding to the Doppler frequency shift amount to which the transmission signal is not allocated is sufficiently lower than the received power level of the Doppler frequency corresponding to the Doppler frequency shift amount to which the transmission signal is allocated (for example, sufficiently low and as low as the noise level).

[0105] MIMO radar using non-uniformly spaced Doppler multiplexing transmission utilizes this property to estimate the reception Doppler frequency of reflected waves from target objects and perform demultiplexing processing of the transmission antennas.

[0106] For example, the reception Doppler frequency of the reflected wave from the target is set to "fd target In this case, the Doppler frequency fd is observed in the output of Doppler frequency detection (for example, relative speed detection) performed by applying Fourier frequency analysis to the radar reflected wave reception signal. target +Δfd1 and fd target The reception level of +Δfd2 is high (for example, above the threshold). On the other hand, in the output of Doppler frequency detection (for example, relative speed detection) using Fourier frequency analysis, the following is observed: target +Δfd1 and fd target +Δfd2 reception level compared to the Doppler frequency fd target The reception level of +Δfd3 is sufficiently low and is as low as the noise level.

[0107] In addition, in the output of Doppler frequency detection (for example, relative speed detection) performed by applying Fourier frequency analysis, observation is performed within the range of -1 / (2Tr)≦fd<1 / (2Tr). Therefore, when this range is exceeded, it will be observed as a signal aliased within -1 / (2Tr)≦fd<1 / (2Tr) in the output applied with Fourier frequency analysis.

[0108] If the received Doppler frequency fd of the reflected wave from the target target In -1 / (2Tr)≦fd target <1 / (2Tr), then the receiving Doppler frequency that satisfies the above relationship is -1 / (2Tr)≦fd target<1 / (2Tr) is unique, so the MIMO radar using non-uniformly spaced Doppler multiplexing can unambiguously determine the Doppler frequency fd of the target within this range. target MIMO radar using non-uniformly spaced Doppler multiplexing transmission, for example, determines the Doppler frequency fd corresponding to the target target In this case, the receiving Doppler frequency of each transmitting antenna can be determined, thereby enabling demultiplexing reception of Doppler multiplexed signals.

[0109] By adopting such demultiplexing reception processing of Doppler multiplexed signals, a MIMO radar using non-equally spaced Doppler multiplexing transmission can, for example, estimate the Doppler frequency of radar reflected waves in the Doppler frequency range of ±1 / (2Tr). By performing non-equally spaced Doppler multiplexing transmission, the detectable Doppler frequency range is expanded to ±1 / (2Tr). For example, by performing non-equally spaced Doppler multiplexing transmission, the detectable Doppler frequency range is expanded to Nt times compared to the method of Patent Document 3.

[0110] [About the application of non-uniformly spaced Doppler multiplexing transmission in multi-beam transmission MIMO radar]

[0111] As described above, in non-equally spaced Doppler multiplexing, for example, unlike equally spaced Doppler multiplexing, a portion of the Doppler frequency domain is not allocated to the transmitted signal, and the MIMO radar performs demultiplexing processing on the Doppler multiplexed signal that estimates the Doppler frequency of the target based on the received power of the received Doppler frequency of the reflected wave from the target.

[0112] Therefore, when non-uniformly spaced Doppler multiplexing is applied to a multi-beam transmission MIMO radar, the following situation can be envisaged.

[0113] In a multi-beam transmission MIMO radar, for example, a phenomenon may occur in which the reception level of the reflected wave varies greatly depending on the beam direction (or transmission beam direction) and the target direction. In a multi-beam transmission MIMO radar, the reception level of the reflected wave from the transmitting antenna may vary greatly between the case where the beam direction coincides with the target direction and the case where the beam direction does not coincide with the target direction. Therefore, in a multi-beam transmission MIMO radar, when multiplexing transmission is performed using non-equally spaced Doppler multiplexing, if the difference in the reception level of the reflected wave between the multi-beams in different beam directions is large, demultiplexing of Doppler multiplexing based on non-equally spaced Doppler multiplexing becomes difficult. If demultiplexing of Doppler multiplexing becomes difficult, degradation of the detection performance of the target in the MIMO radar, or demultiplexing errors of Doppler multiplexing, Doppler misestimation, or degradation of the angle measurement performance may occur.

[0114] Next, an example in which demultiplexing of Doppler multiplexing is difficult in a multi-beam transmission MIMO radar to which non-uniformly spaced Doppler multiplexing is applied will be described.

[0115] For example, a 4Tx MIMO radar including two transmission antennas in each of two beam directions is described. For example, the number of transmission antennas corresponding to each of the two beam directions is represented as “N TxBeam#1 ” and “N TxBeam#2 ”(N TxBeam#1 =N TxBeam#2 =2).

[0116] For example Figure 4 The structure of the multi-beam transmission MIMO radar shown in FIG. 1 is described below. In this radar, for example, two transmission antennas among four transmission antennas Tx#1 to #4 are used to form each transmission beam (TxBeam#1, TxBeam#2) in two different directions. Figure 4 In the example, the transmission beam (beam direction) of Tx#1 and Tx#2 is TxBeam#1, and the transmission beam (beam direction) of Tx#3 and Tx#4 is TxBeam#2. In addition, for example, the directional characteristics of the receiving antenna can be non-directional, or a directional characteristic that is approximately uniform within the field of view (FOV) covered by multiple transmitting antennas with different directivities.

[0117] For example, for 4 transmitting antennas Tx#1 to Tx#4, Figure 5 The following describes the case where Doppler multiplexing signals are allocated at unequal intervals as shown in (a). Figure 5 In the figure, the unit of Doppler frequency shift interval is Δfd=1 / (5Tr), the transmitting Doppler frequencies (Hz) allocated to transmitting antennas Tx#1~Tx#4 are Doppler frequency shift amounts Δfd1=-1 / (2Tr), Δfd2=-3 / (10Tr), Δfd3=-1 / (10Tr), Δfd4=1 / (10Tr), and the transmitting Doppler frequency indicated by the "×" mark is the Doppler frequency shift amount Δfd5=3 / (10Tr). The "×" mark indicates the case where no transmitting antenna is allocated.

[0118] For example, in the direction of the object Figure 4 In the case of the target object direction (1) shown in FIG. 1 , the direction of the reflected wave corresponding to the radar transmission wave transmitted from Tx#1 and Tx#2 forming TxBeam#1 is consistent with the target object direction (1). Therefore, Figure 5 As shown in (b), the reception level (for example, the reflected wave reception level) of the received signal corresponding to Tx#1 and Tx#2 forming TxBeam#1 is high. Figure 4In the case of the target object direction (1) shown in FIG. 1 , the direction of the reflected wave corresponding to the radar transmission wave transmitted from Tx#3 and Tx#4 forming TxBeam#2 does not coincide with the target object direction (1), and the target object direction (1) corresponds to the directivity zero direction (hereinafter also referred to as "zero direction") of TxBeam#2. Therefore, for example, Figure 5 As shown in (b), the reception level of the reception signal corresponding to Tx#3 and Tx#4 forming TxBeam#2 is lower than the reception level of the reception signal corresponding to TxBeam#1 (Tx#1 and Tx#2). For example, the reception level corresponding to TxBeam#2 is greatly different from the reception level corresponding to TxBeam#1, and may be smaller by more than 10 dB depending on the beam pointing characteristics of the null azimuth of TxBeam#2.

[0119] In addition, for example, when the target object direction is the middle direction between the beam direction of TxBeam#1 and the beam direction of TxBeam#2, and the target object direction is in the direction of the region where the beam widths of the two beams overlap by about 3 dB or 6 dB (for example, in the case of Figure 4 In the case of the object direction (2) shown in the figure), Figure 5 As shown in (c), the reflected wave corresponding to the radar transmission wave transmitted from Tx#1 and Tx#2 forming TxBeam#1 and the reflected wave corresponding to the radar transmission wave transmitted from Tx#3 and Tx#4 forming TxBeam#2 are received at the same level.

[0120] In addition, for example, in the direction of the object Figure 4 In the case of the target object direction (3) shown in FIG. 1 , the direction of the reflected wave corresponding to the radar transmission wave transmitted from Tx#3 and Tx#4 forming TxBeam#2 is consistent with the target object direction (3). Therefore, Figure 5 As shown in (d), the reception level (for example, the reflected wave reception level) of the received signal corresponding to Tx#3 and Tx#4 forming TxBeam#2 is high. Figure 4 In the case of the target direction (3) shown in FIG. 1 , the direction of the reflected wave corresponding to the radar transmission wave transmitted from Tx#1 and Tx#2 forming TxBeam#1 does not coincide with the target direction (3), and the target direction (3) is equivalent to the zero direction of TxBeam#1. Figure 5As shown in (d), the reception level of the reception signal corresponding to Tx#1 and Tx#2 forming TxBeam#1 is lower than the reception level of the reception signal corresponding to TxBeam#2 (Tx#3 and Tx#4). For example, the reception level corresponding to TxBeam#1 is greatly different from the reception level corresponding to TxBeam#2, and may be smaller by more than 10 dB depending on the beam pointing characteristics of the null azimuth of TxBeam#1.

[0121] For example, in Figure 5 In the case of (c), the reception level of the reflected wave corresponding to the radar transmission wave transmitted from Tx#1 and Tx#2 forming TxBeam#1 and the reception level of the reflected wave corresponding to the radar transmission wave transmitted from Tx#3 and Tx#4 forming TxBeam#2 are about the same. The multi-beam transmission MIMO radar can determine which transmission antenna used in the non-uniformly spaced Doppler multiplexing transmission corresponds to the peak of the detected Doppler frequency based on the reception levels of these received signals. In addition, Figure 5 In (c), the Doppler frequency fd of the target object reflected wave can be determined in the range of -1 / (2Tr)≦fd<1 / (2Tr).

[0122] On the other hand, Figure 5 (b) or Figure 5 In the case of (d), since the Doppler frequency of the target object is unknown, it is difficult for the multi-beam transmission MIMO radar to determine based on the reception level of the received signal that the reception level of the reflected wave corresponding to the radar transmission wave transmitted from Tx#1 and Tx#2 forming TxBeam#1 has decreased (for example, Figure 5 In the case of (d), the reception level of the reflected wave corresponding to the radar transmission wave transmitted from Tx#3 and Tx#4 forming TxBeam#2 is lowered (for example, Figure 5 (b)). Therefore, it is difficult for the multi-beam transmission MIMO radar to determine, based on the reception level of the received signal, which transmission antenna used in the non-uniformly spaced Doppler multiplexing transmission corresponds to the peak of the detected Doppler frequency. Therefore, it is difficult for the multi-beam transmission MIMO radar to demultiplex the Doppler multiplexing signal and to determine the Doppler frequency fd of the reflected wave from the target (for example, called "target reflected wave") in the range of -1 / (2Tr)≦fd<1 / (2Tr).

[0123] Thus, in the case of non-uniformly spaced Doppler multiplexing, the demultiplexing process of Doppler multiplexing is performed on the premise that the reception levels of the reflected waves corresponding to the respective transmission antennas are equal and the reception levels of the Doppler frequency shift intervals (× marks) that are not Doppler multiplexed are sufficiently low to the level of noise level. Figure 5 As shown in (b) and (d), there is a situation where the premise of the demultiplexing processing of non-uniformly spaced Doppler multiplexing does not hold (a situation where the reception level corresponding to a part of the beams decreases), and the demultiplexing processing of Doppler multiplexing may be performed erroneously.

[0124] As another example, Figure 6 The following describes a case where unequally spaced Doppler multiplexed signals are allocated to four transmission antennas Tx#1 to Tx#4 as shown in (a). Figure 6 In (a), the unit of Doppler frequency shift interval is Δfd=1 / (6Tr), the transmitting Doppler frequencies (Hz) allocated to transmitting antennas Tx#1~Tx#4 are Doppler frequency shift amounts Δfd1=-1 / (2Tr), Δfd2=-1 / (3Tr), Δfd3=-1 / (6Tr), and Δfd4=0, respectively. The transmitting Doppler frequencies represented by the two "×" marks are Doppler frequency shift amounts Δfd5=1 / (6Tr) and Δfd6=1 / (3Tr), respectively. The "×" mark indicates the case where no transmitting antenna is allocated.

[0125] For example, the transmission beams (beam directions) of Tx#1 and Tx#4 are set to Figure 4 The TxBeam#1 shown in the figure sets the transmit beam (beam direction) of Tx#2 and Tx#3 to Figure 4 TxBeam#2 is shown. In the direction of the target object Figure 4 In the case of the object direction (1) shown in FIG. Figure 6 The receiving level of the received signal shown in (b) is Figure 4 In the case of the object direction (2) shown in FIG. Figure 6 The receiving level of the received signal shown in (c) is Figure 4 In the case of the object direction (3) shown in FIG. Figure 6 The reception level of the received signal shown in (d).

[0126] For example, in Figure 6In the case of (c), the reception level of the reflected wave corresponding to the radar transmission wave transmitted from Tx#1 and Tx#4 of TxBeam#1 is about the same as the reception level of the reflected wave corresponding to the radar transmission wave transmitted from Tx#2 and Tx#3 of TxBeam#2. The multi-beam transmission MIMO radar can determine which transmission antenna used in the non-uniformly spaced Doppler multiplexing transmission corresponds to the peak of the detected Doppler frequency based on the reception levels of these received signals. In addition, Figure 6 In (c), the Doppler frequency fd of the target object reflected wave can be determined in the range of -1 / (2Tr)≦fd<1 / (2Tr).

[0127] On the other hand, Figure 6 (b) or Figure 6 In the case of (d), since the Doppler frequency of the target object is unknown, it is difficult for the multi-beam transmission MIMO radar to determine based on the reception level of the received signal whether the reception level of the reflected wave corresponding to the radar transmission wave transmitted from Tx#1 and Tx#4 of TxBeam#1 has decreased, or the reception level of the reflected wave corresponding to the radar transmission wave transmitted from Tx#2 and Tx#3 of TxBeam#2 has decreased. Therefore, it is difficult for the multi-beam transmission MIMO radar to determine based on the reception level of the received signal which transmission antenna used in the non-uniformly spaced Doppler multiplexing transmission corresponds to the peak of the detected Doppler frequency. Therefore, it is difficult for the multi-beam transmission MIMO radar to demultiplex the Doppler multiplexing signal and determine the Doppler frequency fd of the target object reflection wave in the range of -1 / (2Tr)≦fd<1 / (2Tr).

[0128] In a non-limiting embodiment of the present disclosure, a method for improving the detection performance of a multi-beam transmission MIMO radar using non-equally spaced Doppler multiplexing transmission is described.

[0129] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. In the embodiments, the same components are given the same reference numerals, and their descriptions are omitted to avoid duplication.

[0130] The following describes a structure (for example, a MIMO radar structure) in which a radar device simultaneously sends out different multiplexed transmission signals from a plurality of transmission antennas in a transmission branch, and demultiplexes each transmission signal in a reception branch to perform reception processing.

[0131] In addition, as an example, the following describes a radar method that uses a frequency-modulated pulse wave such as a chirp pulse (for example, also referred to as "fast chirp modulation"). However, the modulation method is not limited to frequency modulation. For example, one embodiment of the present disclosure may also be applied to a radar method that uses a pulse compression radar that transmits a pulse train by phase modulation or amplitude modulation.

[0132] In addition, the radar device may perform, for example, Doppler multiplexing transmission (for example, non-uniformly spaced Doppler multiplexing transmission). In addition, the radar device may include, for example, a plurality of transmission antennas having different directional characteristics.

[0133] [Structure of radar device]

[0134] Figure 7 The radar device 10 includes a radar transmitting unit (transmitting branch) 100 and a radar receiving unit (receiving branch) 200 .

[0135] The radar transmitting unit 100 generates a radar signal (radar transmission signal), and transmits the radar transmission signal at a predetermined transmission cycle (eg, referred to as a “radar transmission cycle”) using a transmission antenna unit 105 including a plurality of transmission antennas (eg, Nt).

[0136] The radar receiving unit 200 receives the radar transmission signal reflected by the target (target, not shown) using the receiving antenna unit 202 including a plurality of receiving antennas, that is, the reflected wave signal. The radar receiving unit 200 performs signal processing on the reflected wave signal received by each receiving antenna of the receiving antenna unit 202, for example, detecting the presence of the target, or estimating the arrival distance, Doppler frequency (for example, relative speed), and arrival direction of the reflected wave signal, and outputs information related to the estimation result (for example, positioning information).

[0137] In addition, the radar device 10 can be mounted on a mobile object such as a vehicle, and the positioning output from the positioning output unit 300 (for example, information related to the estimation result) can also be connected to a control device ECU (Electronic Control Unit) (not shown) such as an advanced driver assistance system (ADAS) or an automatic driving system that improves collision safety, for vehicle drive control or alarm call control.

[0138] In addition, the radar device 10 can be installed on a higher structure such as a roadside electric pole or a traffic light (not shown). In addition, the radar device 10 can also be used as a sensor in an auxiliary system for improving the safety of passing vehicles or pedestrians or a system to prevent suspicious people from breaking into the road (not shown). In addition, the positioning output of the radar receiving unit 200 can also be connected to a control device (not shown) in an auxiliary system for improving safety or a system to prevent suspicious people from breaking into the road, for example, for alarm call control or abnormality detection control. In addition, the use of the radar device 10 is not limited to this, and it can also be used for other purposes.

[0139] The target object is an object to be detected by the radar device 10 , and includes, for example, a vehicle (including four-wheeled and two-wheeled vehicles), a person, a rock, a curb, and the like.

[0140] [Configuration of Radar Transmitting Unit 100]

[0141] The radar transmitting unit 100 includes a radar transmission signal generating unit 101, a Doppler frequency shift unit 104, and a transmission antenna unit 105. The radar transmission signal generating unit 101 and the Doppler frequency shift unit 104 may be collectively referred to as a "transmission circuit".

[0142] The radar transmission signal generating unit 101 generates a radar transmission signal. The radar transmission signal generating unit 101 includes, for example, a modulation signal generating unit 102 and a VCO (Voltage Controlled Oscillator) 103. Hereinafter, each component of the radar transmission signal generating unit 101 will be described.

[0143] The modulation signal generation unit 102 periodically generates a sawtooth-shaped modulation signal, for example.

[0144] The VCO 103 generates a frequency modulation signal (hereinafter, for example, referred to as a frequency chirp signal or a chirp signal) based on the modulation signal input from the modulation signal generator 102. Figure 8 The radar transmission signal (radar transmission wave) shown is output to the Doppler frequency shift unit 104 and the radar receiving unit 200 (mixer unit 204 described later).

[0145] In the following, the modulation signal generator 102 generates a modulation signal so that the chirp signal is transmitted Nc times in each transmission cycle Tr in one radar positioning. The VCO 103 outputs the chirp signal Nc times in each transmission cycle Tr according to the operation of the modulation signal generator 102.

[0146] The radar device 10 can detect temporal variation in the position of the target object by, for example, performing radar positioning a plurality of times.

[0147] In addition, below, each transmission cycle in the Nc transmission cycles Tr is represented by an index "m". Here, m=1 to Nc.

[0148] Fig. 9 An example of a chirp signal output from the radar transmission signal generation unit 101 is shown.

[0149] like Fig. 9 As shown, the modulation parameters associated with the chirp signal may include, for example, the center frequency f c , Frequency scanning bandwidth B w , Scan start frequency f cstart , scanning end frequency f cend , frequency scanning time T sw And the frequency sweep rate D m In addition, D m =B w / T sw In addition, B w =f cend -f cstart , and f c =(f cstart +f cend ) / 2.

[0150] In addition, the frequency sweep time T sw For example, it corresponds to the time range (or “range gate”) during which the AD (Analog Digital) converter 207 of the radar receiver 200 described later acquires A / D sample data. sw For example, Fig. 9 As shown in (a) of FIG. 1 , the entire interval of the chirp signal can also be set as Fig. 9 As shown in (b), the interval is set as a part of the chirp signal.

[0151] In addition, Figure 8 and Fig. 9 , an example of an up-chirp waveform in which the modulation frequency gradually increases over time is shown, but the present invention is not limited thereto, and a down-chirp waveform in which the modulation frequency gradually decreases over time may also be applied. Regardless of whether the modulation frequency is up-chirp or down-chirp, the same effect can be obtained.

[0152] The chirp signal output from the radar transmission signal generation unit 101 is input to each of the Nt Doppler frequency shift units 104. In addition, the chirp signal is also input to each of the mixer units 204 of the radar reception unit 200.

[0153] The n-th Doppler frequency shift unit 104 is used to give a Doppler frequency shift amount DOP to the chirp signal input from the radar transmission signal generation unit 101.n , giving a phase rotation Φ according to the transmission period Tr of the chirp signal n (m). The nth Doppler frequency shift unit 104 gives a phase rotation Φ n The chirp signal (m) is output to the nth transmission antenna (for example, Tx#n) of the transmission antenna unit 105. Here, n=1 to Nt.

[0154] The transmitting antenna unit 105 may include Nt transmitting antennas Tx#1 to Tx#Nt. The transmitting antennas Tx#1 to Tx#Nt may constitute a multi-beam transmitting radar including at least two transmitting antennas with different main beam directions (or beam directions). For example, the Doppler frequency shift unit 104 may give a phase rotation Φ with different Doppler frequency shift amounts to the chirp signal according to the structure of the transmitting antennas corresponding to the multiple beam directions in the transmitting antenna unit 105, according to the transmitting antennas that transmit the chirp signal. n (m), and outputs it to the transmission antenna unit 105. Thus, even when the reception levels (for example, the reception power levels of reflected waves) between the reception signals of the transmission antennas corresponding to different beam directions are greatly different (for example, when the reception level difference or the reception level ratio is equal to or greater than the threshold), the radar device 10 can demultiplex the Doppler multiplexed signal, and can reduce the degradation of the positioning performance and the radar detection performance (an operation example will be described later).

[0155] The outputs from the Nt Doppler frequency shift units 104 are amplified to predetermined transmission power and then radiated into space from the transmission antennas Tx# 1 to Tx#Nt of the transmission antenna unit 105 .

[0156] [Configuration of the radar receiving unit 200]

[0157] exist Figure 7 In the embodiment, the radar receiving unit 200 has a receiving antenna unit 202 including Na receiving antennas Rx#1 to Rx#Na. In addition, the radar receiving unit 200 includes Na antenna system processing units 201-1 to 201-Na, a CFAR (Constant False Alarm Rate) unit 210, a Doppler multiplexing and demultiplexing unit 211, and a direction estimation unit 212. In addition, the Na antenna system processing units 201-1 to 201-Na, the CFAR unit 210, the Doppler multiplexing and demultiplexing unit 211, and the direction estimation unit 212 can be collectively referred to as a "receiving circuit". In addition, the receiving circuit uses the reflected wave signal reflected by the transmission signal at the target (target) to estimate the direction of the target.

[0158] The receiving antennas Rx#1 to Rx#Na of the receiving antenna unit 202 receive reflected wave signals, which are radar transmission signals reflected by a target object (object), and output the received reflected wave signals to the corresponding antenna system processing unit 201 as received signals.

[0159] Each antenna system processing unit 201 includes a reception radio unit 203 and a signal processing unit 206 .

[0160] Each signal received by Na receiving antennas Rx#1 to Rx#Na is output to Na receiving wireless units 203. In addition, output signals from Na receiving wireless units 203 are output to Na signal processing units 206, respectively.

[0161] The receiving wireless unit 203 includes a mixer unit 204 and an LPF (low pass filter) 205. The mixer unit 204 mixes the received reflected wave signal with the chirp signal input from the radar transmission signal generating unit 101. The receiving wireless unit 203, for example, passes the output of the mixer unit 204 through the LPF 205. As a result, a beat signal having a frequency corresponding to the delay time of the reflected wave signal is output. For example, Fig.10 As shown, the difference frequency between the frequency of the transmission chirp signal (transmission frequency modulation wave) as the transmission signal (radar transmission wave) and the frequency of the reception chirp signal (reception frequency modulation wave) as the reception signal (radar reflection wave) is obtained as the beat frequency.

[0162] The signal processing unit 206 in each antenna system processing unit 201 - z (where z=any one of 1 to Na) includes an AD conversion unit 207 , a beat frequency analysis unit 208 , and a Doppler analysis unit 209 .

[0163] The signal (for example, the beat signal) output from the LPF 205 is converted into discrete sample data by the AD converter 207 in the signal processing unit 206 through discrete sampling.

[0164] The beat frequency analysis unit 208 analyzes the N signals obtained within a predetermined time range (range gate) according to the transmission period Tr. data The signal processing unit 206 performs frequency analysis processing (e.g., FFT processing) on ​​discrete sample data. As a result, the signal processing unit 206 outputs a frequency spectrum having a peak at the beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave). In addition, when performing FFT processing, the beat frequency analysis unit 208 may also multiply the window function coefficients such as the Han window or the Hamming window. By using the window function coefficients, the side lobes generated around the peak of the beat frequency can be suppressed.

[0165] In addition, in N dataWhen it is not a power of 2, for example, by including zero-padded data, FFT processing can be performed with a data size (FFT size) that is a power of 2. In this case, by considering the data size including zero-padded data as N data , can be processed in the same way as above.

[0166] Here, the beat frequency response obtained by transmitting the m-th chirped pulse and outputted from the beat frequency analysis unit 208 in the z-th signal processing unit 206 is represented by “RFT z (f b , m)”. Here, f b represents the beat frequency index, which corresponds to the index (bin number) of the FFT. b =0, ..., (N data / 2)-1, z=1~Na, m=1~N C . Beat frequency index f b The smaller the beat frequency, the smaller the delay time of the reflected wave signal (for example, the closer the distance to the target object).

[0167] In addition, the beat frequency index f b It can be converted into distance information R(f b ). Therefore, in the following, the beat frequency index f b It is called the “distance index f b ”.

[0168] [Formula 1]

[0169]

[0170] Here, B w represents the frequency modulation bandwidth within the range gate of the chirp signal, and C0 represents the speed of light. In addition, in formula (1), C0 / (2B w ) represents the distance resolution.

[0171] The Doppler analysis unit 209 in the z-th signal processing unit 206 uses the data of the Nc transmission cycles of the chirp signal (for example, the beat frequency response RFT input from the beat frequency analysis unit 208) to analyze the chirp signal. z (f b ,1),RFT z (f b , 2), ..., RFT z (f b , Nc)), for each distance index f b Doppler analysis was performed.

[0172] For example, when Nc is a power of 2, the Doppler analysis unit 209 can apply FFT processing to the Doppler analysis as shown in the following equation (2).

[0173] [Formula 2]

[0174]

[0175] Here, the FFT size is Nc, and the maximum Doppler frequency that does not cause aliasing is ±1 / (2Tr) according to the sampling theorem. In addition, the Doppler frequency index f s The Doppler frequency interval is 1 / (Nc×Tr), and the Doppler frequency index f s The range is f s = -Nc / 2, ..., 0, ..., (Nc / 2) - 1. In addition, j is an imaginary unit, and z = 1 to Na.

[0176] As an example, the case where Nc is a power of 2 is described below. In addition, when Nc is not a power of 2, for example, by including zero-filled data, FFT processing can be performed with a power of 2 as the data size (FFT size). In addition, when performing FFT processing, the Doppler analysis unit 209 can also multiply the window function coefficient such as the Hanning window or the Hamming window. By applying the window function, the side lobes generated around the Doppler frequency peak can be suppressed.

[0177] The above describes the processing in each component of the signal processing unit 206.

[0178] exist Figure 7 In the CFAR processing, the CFAR unit 210 uses the outputs of the Doppler analysis units 209 of the first to Nath signal processing units 206 to perform CFAR processing (for example, adaptive threshold determination). For example, in the CFAR processing, the local peak of the reflected wave reception signal of the radar transmission signal sent from the transmission antenna unit 105 can be selectively extracted to perform adaptive threshold determination. The CFAR unit 210 extracts, for example, the distance index f that gives the local peak signal. b_cfar and the Doppler frequency index f s_cfar , and output to the Doppler multiplexing and demultiplexing unit 211.

[0179] The Doppler multiplexing and demultiplexing unit 211 uses, for example, the output of the Doppler analysis unit 209 of the 1st to Nath signal processing units 206 and the output of the CFAR unit 210 to demultiplex the radar reflected wave reception signals of each radar transmission signal sent from multiple transmitting antennas using Doppler multiplexing (hereinafter referred to as "Doppler multiplexing demultiplexing").

[0180] In addition, for example, the operation of the Doppler multiplexing and demultiplexing unit 211 is associated with the operation of the Doppler frequency shift unit 104 of the radar transmitting unit 100. Similarly, for example, the operation of the CFAR unit 210 is associated with the operation of the Doppler frequency shift unit 104. Below, an operation example of the Doppler frequency shift unit 104 is described, and then an operation example of the CFAR unit 210 and an operation example of the Doppler multiplexing and demultiplexing unit 211 are described.

[0181] [Operation Example of Doppler Shifter 104 in Radar Transmitter 100]

[0182] For example, the first to Ntth Doppler shift units 104 give different Doppler shift amounts DOP to the radar transmission signals input thereto. n The radar device 10 transmits radar transmission signals to which the Doppler shift unit 104 has given phase rotations corresponding to the Doppler shift amounts allocated to the Nt transmission antennas, respectively, from the Nt transmission antennas (Doppler multiplexing transmission).

[0183] In addition, an example in which a chirp signal is used as a radar transmission signal will be described below.

[0184] For example, the n-th Doppler frequency shift unit 104 provides a predetermined Doppler frequency shift amount DOP to the n-th transmission antenna Tx#n. n , and a phase rotation Φ is given according to the transmission period Tr of the input chirp signal n Here, the Doppler frequency shift unit 104 may provide a phase rotation φ that causes a different Doppler frequency shift to the chirp signal for each transmitting antenna that transmits the chirp signal. n (m) and output. Here, n = 1 to Nt. For example, the phase rotation Φ given to each transmission period Tr of the chirp signal n (m) can use Φ n (m)=2πDOP n ×Tr to set.

[0185] For example, the transmitting antennas Tx#1 to Tx#Nt of the transmitting antenna unit 105 constitute a multi-beam transmitting radar including at least transmitting antennas corresponding to two different beam directions (for example, transmitting antennas that form beams in at least two different directions). For example, the Doppler frequency shift unit 104 can consider the structure of the transmitting antennas Tx#1 to Tx#Nt in different beam directions, and give the chirp signal a phase rotation Φ that causes a different Doppler frequency shift according to the transmitting antenna that transmits the chirp signal. nThus, even when the reception power levels of reflected waves are greatly different between the reception signals corresponding to the chirp signals transmitted from the transmission antennas in different beam directions, the radar device 10 can demultiplex the Doppler multiplexed signals, thereby improving the positioning performance and radar detection performance of the radar device 10.

[0186] In addition, the transmission antennas Tx#1 to Tx#Nt may include a plurality of transmission antennas corresponding to different beam directions. In addition, the transmission antennas Tx#1 to Tx#Nt may include a plurality of transmission antennas corresponding to the same beam direction.

[0187] The radar device 10 is, for example, a multi-beam transmission MIMO radar using Nt transmission antennas Tx#1 to Tx#Nt including transmission antennas with different beam directions, and can use the Nt transmission antennas Tx#1 to Tx#Nt to perform unequally spaced Doppler multiplexing transmission.

[0188] Furthermore, the radar device 10 may use Doppler multiplexing transmission that satisfies the following condition 1, for example, to multiplex and transmit radar transmission signals simultaneously from Nt transmission antennas Tx# 1 to Tx#Nt.

[0189] In the following description, the first beam direction (or beam) among the multiple beam directions (or beams) used in the multi-beam transmission MIMO radar is described as "B1", and the second beam direction (or beam) is described as "B2". In addition, for example, the qth beam direction (or beam) is described as "Bq". q is an integer value within the number of different beam directions (for example, the number of multi-beams NB). For example, when the number of multi-beams NB = 2, q = 1 or 2.

[0190] In addition, let the number of transmission antennas Nt ≥ 3. For example, let the number of Doppler multiplexing N DDM ≧3. In addition, the number of transmission antennas is not limited to Nt≧3, and for example, Nt = 2. In addition, the case of Nt = 2 will be described in the following modification example 1.

[0191] In the transmission antenna unit 105, the number of transmission antennas corresponding to the beam direction B1 is N. B1 , the number of transmitting antennas corresponding to the beam direction B2 is set to N B2 In this case, N B1 +N B2 =Nt. In addition, the radar device 10 may allocate one Doppler multiplexed signal to one transmission antenna, for example.

[0192] <Condition 1>

[0193] Between the Doppler multiplexed signals respectively allocated to the transmission antenna of the beam direction B1 and the transmission antenna of the beam direction B2, any one of the following conditions is satisfied.

[0194] (1) The Doppler multiplexing number corresponding to each beam direction is the same (for example, N B1 =N B2 It should be noted that in N B1 ≧2, N B2 ≧2, in N NB1 =N NB2 =1, no need to consider), and in each beam direction, it contains different Doppler frequency shift intervals.

[0195] (2) The Doppler multiplexing number (or number of transmitting antennas) in each beam direction is different (N B1 ≠N B2 ).

[0196] (3) In N B1 ≧3, N B2 ≧3, the Doppler multiplexing number corresponding to each beam direction is the same (N B1 =N B2 ), and when the Doppler frequency shift intervals of each beam direction include the same Doppler frequency shift interval, the order of the Doppler frequency shift intervals is different.

[0197] In addition, the radar device 10 can use Doppler multiplexing transmission that further satisfies the following condition 2, for example, and multiplex and transmit radar transmission signals simultaneously from Nt transmission antennas Tx# 1 to Tx#Nt.

[0198] <Condition 2>

[0199] Doppler multiplexing signals are allocated to the beam direction B1 and the beam direction B2 respectively in such a manner as to achieve the following non-uniformly spaced Doppler multiplexing:

[0200] The unequally spaced Doppler multiplexing of the transmitting antennas based on the beam direction B1 (it should be noted that in N B1 ≧2, in N NB1 =1, no need to consider);

[0201] The unequally spaced Doppler multiplexing of the transmitting antennas based on the beam direction B2 (it should be noted that in N B2 ≧2, in N NB2 = 1, no need to consider).

[0202] For example, according to condition 1 (1), if the Doppler multiplexing number N of the transmitting antenna based on the beam direction B1 is B1 The Doppler multiplexing number N of the transmitting antenna based on the beam direction B2 B2If the transmission direction B1 and the transmission direction B2 are the same, at least one of the intervals of the Doppler frequency shift amounts assigned to the transmission antennas in the beam direction B1 (Doppler frequency shift intervals) is different from the intervals of the Doppler frequency shift amounts assigned to the transmission antennas in the beam direction B2. As examples of (1) of condition 1, there can be cited a case where the maximum Doppler frequency shift intervals between the Doppler multiplexed signals assigned to the transmission antennas in the beam direction B1 and the beam direction B2 are different, a case where the minimum Doppler frequency shift intervals are different, or a case where the Doppler frequency shift intervals that are neither the maximum nor the minimum are different.

[0203] For example, if condition 1 (2) is met, the Doppler multiplexing number (for example, the number of transmitting antennas) N of the transmitting antenna based on the beam direction B1 may be B1 The Doppler multiplexing number (eg, the number of transmitting antennas) N of the transmitting antenna based on the beam direction B2 B2 different.

[0204] In addition, for example, according to condition 1 (3), if the Doppler multiplexing number N of the transmitting antenna based on the beam direction B1 is B1 The Doppler multiplexing number N of the transmitting antenna based on the beam direction B2 B2 The same is true, and the values ​​of the multiple intervals of Doppler frequency shift amounts allocated to the transmitting antenna in beam direction B1 and the transmitting antenna in beam direction B2 are the same (for example, the combination of Doppler frequency shift intervals), then the order of the multiple Doppler frequency shift intervals corresponding to the transmitting antenna in beam direction B1 on the Doppler frequency axis is different from the order of the multiple Doppler frequency shift intervals corresponding to the transmitting antenna in beam direction B2 on the Doppler frequency axis.

[0205] For example, a combination of intervals contained in a sequence (for example, a first sequence) in which the intervals of the Doppler frequency shift amounts assigned to the transmitting antennas in beam direction B1 are arranged in sequence from the smaller side on the Doppler frequency axis is consistent with a combination of intervals contained in a sequence (for example, a second sequence) in which the intervals of the Doppler frequency shift amounts assigned to the transmitting antennas in beam direction B2 are arranged in sequence from the smaller side on the Doppler frequency axis, and the first sequence and the second sequence are different sequences when arranged in a circle.

[0206] When condition 1 (3) is satisfied, even if one of the Doppler shift intervals of the transmitting antennas in beam direction B1 and the Doppler shift intervals of the transmitting antennas in beam direction B2 is cyclically shifted in the Doppler frequency domain, the two will not match.

[0207] In addition, for example, according to condition 2, on the Doppler frequency axis, the intervals of the Doppler frequency shift amounts assigned to the transmitting antennas in the beam direction B1 are set to be unequal intervals. Similarly, according to condition 2, on the Doppler frequency axis, the intervals of the Doppler frequency shift amounts assigned to the transmitting antennas in the beam direction B2 are set to be unequal intervals. In condition 2, unequal interval Doppler multiplexing transmission may be applied to one or both of the beam directions B1 and B2.

[0208] Thus, in the non-equally spaced Doppler multiplexing transmission performed by the radar device 10 which is a multi-beam transmission MIMO radar, the intervals of the Doppler shift amounts assigned to the plurality of transmission antennas included in the transmission antenna unit 105 are non-equally spaced on the Doppler frequency axis. In addition, for example, the pattern of the Doppler shift amounts assigned to the transmission antennas in the beam direction B1 (for example, a pattern related to the Doppler shift interval, or the number of transmission antennas (Doppler multiplexing number), or the order of the intervals of the Doppler shift amounts on the Doppler frequency axis) is different from the pattern of the Doppler shift amounts assigned to the transmission antennas in the beam direction B2 (corresponding to condition 1).

[0209] Therefore, even if the reception power levels of reflected waves differ greatly between reception signals from transmission antennas in different beam directions, the radar device 10 can demultiplex the Doppler multiplexed signal in this case, thereby suppressing degradation of positioning performance and radar detection performance.

[0210] In addition, for example, among the multiple transmitting antennas included in the transmitting antenna unit 105, the intervals of the Doppler frequency shift amounts assigned to the transmitting antennas corresponding to the multiple beam directions are non-equal intervals (corresponding to condition 2). By satisfying condition 2, the Doppler frequency range detectable by the radar device 10 reaches the range of -1 / (2Tr)≦fd<1 / (2Tr), which can be expanded to a range greater than the Doppler detection range of -1 / (2N) in the case of equal-interval Doppler multiplexing transmission. t Tr)≦fd<1 / (2N t Tr) Larger range.

[0211] For example, in the Doppler multiplexing transmission of the radar device 10, both conditions 1 and 2 may be satisfied, or condition 1 may be satisfied but condition 2 may not be satisfied. The following three cases are examples of cases where condition 1 is satisfied but condition 2 is not satisfied.

[0212] (Case 1)

[0213] Case 1 is a case where the transmission antennas in the beam direction B1 and the transmission antennas in the beam direction B2 are equally spaced using Doppler multiplexing (it should be noted that in N B1 ≧2, N B2 ≧2, in N NB1=N NB2 =1). In case 1, the Doppler frequency range fd detectable by the radar device 10 depends on the target direction and is -1 / (2Tr)≦fd<1 / (2Tr), -1 / (2N B1 Tr)≦fd<1 / (2N B1 Tr) or -1 / (2N B2 Tr)≦fd<1 / (2N B2 Tr) this range.

[0214] (Case 2)

[0215] Case 2 is a case where the transmission antennas in the beam direction B1 are non-uniformly spaced Doppler multiplexing, and the transmission antennas in the beam direction B2 are equally spaced Doppler multiplexing (it should be noted that in N B1 ≧2, N B2 ≧2, in N NB1 =N NB2 =1). In case 2, the Doppler frequency range fd detectable by the radar device 10 is -1 / (2Tr)≦fd<1 / (2Tr) or -1 / (2N B2 Tr)≦fd<1 / (2N B2 Tr) this range.

[0216] (Case 3)

[0217] Case 3 is a case where the transmission antennas in the beam direction B1 are equally spaced for Doppler multiplexing, and the transmission antennas in the beam direction B2 are unequally spaced for Doppler multiplexing (it should be noted that in N B1 ≧2, N B2 ≧2, in N NB1 =N NB2 =1). In case 3, the Doppler frequency range fd detectable by the radar device 10 is -1 / (2Tr)≦fd<1 / (2Tr) or -1 / (2N B1 Tr)≦fd<1 / (2N B1 Tr) this range.

[0218] In any of the cases 1 to 3, the detectable Doppler frequency range can be expanded to -1 / (2N t Tr)≦fd<1 / (2N t Tr) Larger range.

[0219] In addition, the Doppler analysis unit 209 performs Doppler frequency analysis on the output of the beat frequency analysis unit 208 of each distance index according to the transmission period Tr. Therefore, the Doppler frequency f that does not cause aliasing derived according to the sampling theorem is d The range is -1 / (2Tr)≦fd<1 / (2Tr). Even if the Doppler frequency exceeds this range, the range of the observed Doppler frequency fd is -1 / (2Tr)≦fd<1 / (2Tr).

[0220] For example, when the Doppler frequency shift unit 104 assigns the Doppler frequency shift amount within the range of -1 / (2Tr)≦fd<1 / (2Tr), the maximum Doppler frequency shift interval for Nt transmission antennas (=Doppler multiplexing number) is Δfdmax=1 / (TrNt)=1 / (TrNt) DM ). For example, the Doppler frequency shift unit 104 may set the Doppler frequency shift interval to an interval smaller than Δfdmax. The phase rotation amount given to such a Doppler frequency shift is For example, in is set within the range of

[0221] In the following description of the operation of the Doppler frequency shift unit 104, when a frequency exceeding Phase rotation of the range When , a phase rotation with the same phase in the range of -π to π can be given Here, α satisfies The integer value of .

[0222] In addition, for example, the Doppler frequency shift interval assigned to the Doppler multiplexed signal by the Doppler frequency shift unit 104 may be set in units of Δfd shown in the following equation (3). Here, δ>0, and δ may be a positive integer or a positive real number. By setting δ to a positive integer, the effect of simplifying the processing in the CFAR unit 210 described later can be obtained. In addition, the following shows a case where δ is a positive integer, but it is not limited to this, and a positive real number may also be used.

[0223] [Formula 3]

[0224] Δfd = 1 / (Tr × (N DM + δ)) (3)

[0225] In addition, when δ is set to a positive integer of δ>1 in equation (3), there are a plurality of Doppler frequency shift amounts to which the Doppler multiplexed signal is not allocated (for example, in the following setting example of the Doppler frequency shift amount, the Doppler frequency shift amount indicated by the "×" mark in the figure used). In this case, for example, by allocating the Doppler multiplexed signal in such a manner that these Doppler frequency shift amounts are not equally spaced, the Doppler frequency range fd detectable by the radar device 10 can be set within the range of -1 / (2Tr)≦fd<1 / (2Tr).

[0226] The following describes an example of setting the Doppler shift amount in the Doppler shift unit 104. In allocating the Doppler shift amount to each transmission antenna, the transmission Doppler frequencies may be allocated in ascending order, descending order, or randomly, and each setting example is merely an example.

[0227] <Doppler shift amount setting example 1>

[0228] Fig.11 Indicates the number of transmitting antennas Nt = 3, N B1 =2,N B2 =1 is an example of setting the pattern of the Doppler shift amount for the transmission Doppler frequency. Fig.11 , Tx#1 and Tx#2 are respectively the transmitting antennas of the beam direction B1 (for example, the transmitting antennas forming the transmitting beam B1), and Tx#3 is the transmitting antenna of the beam direction B2 (for example, the transmitting antennas forming the transmitting beam B2).

[0229] In addition, in the setting example 1 of the Doppler frequency shift amount, if Fig.11 As shown, the basic unit of the Doppler frequency shift interval in the Doppler frequency shift unit 104 is set to Δfd=1 / (Tr×(N DM +δ))=1 / (4Tr), and δ=1, but the value of δ is not limited to this. δ can be a positive integer or a positive real number.

[0230] exist Fig.11 In the illustrated example, the first to third Doppler shift units 104 (or Doppler shift units 104 - 1 , 104 - 2 , and 104 - 3 ) can perform the following operations.

[0231] For example, in order to give the Doppler shift amount DOP1=-1 / (2Tr) to the first transmitting antenna Tx#1, the first Doppler shift unit 104 gives a phase rotation of Φ1(m)=2πDOP1×(m-1)Tr=-π(m-1) according to the transmission period Tr of the chirp signal and outputs it.

[0232] For example, in order to give the second transmitting antenna Tx#2 a Doppler shift amount DOP2=-1 / (4Tr), the second Doppler shift unit 104 gives a phase rotation Φ2(m)=2πDOP2×(m-1)Tr=-π(m-1) / 2 according to the transmission period Tr of the chirp signal and outputs it.

[0233] For example, in order to give the Doppler shift amount DOP3=0 to the third transmission antenna Tx#3, the third Doppler shift unit 104 gives a phase rotation of Φ3(m)=2πDOP3×(m-1)Tr=0 according to the transmission period Tr of the chirp signal and outputs it.

[0234] Hereinafter, the interval between the Doppler frequency shift amounts given to Tx#n1 and Tx#n2 is expressed as the Doppler frequency shift interval “Δfd (n1，n2) ”. Here, Δfd (n1，n2) The Doppler frequency shift Δfd given to Tx#n1 is represented by n1 The Doppler frequency shift Δfd given to Tx#n2 based on the reference n2 The interval (Δfd n2 -Δfd n1 ). In addition, in the Doppler frequency shift interval Δfd (n1，n2) When the value is negative (for example, in (Δfd n2 -Δfd n1 )<0), taking into account the aliasing within the observation range of the Doppler analysis unit 209, that is, within the range of greater than -1 / (2Tr) and less than 1 / (2Tr), Δfd is used. (n1，n2) =1 / Tr-Δfd (n1，n2) To calculate the Doppler frequency shift interval Δfd (n1，n2) , and is expressed as a positive value. The Doppler frequency shift interval Δfd in the following text (n1，n2) The same expression is also used in the records.

[0235] exist Fig.11 In the example, the interval (Doppler shift interval) of the Doppler frequency shift amount given to each transmitting antenna Tx#1, Tx#2, and Tx#3 is Δfd (1，2) =Δfd,Δfd (2，3) =Δfd,Δfd (3，1) =2Δfd. Therefore, Fig.11 In the example, the intervals of the Doppler frequency shift amounts given to the respective transmitting antennas when the number of transmitting antennas Nt=3 are not all the same, but include unequal intervals (for example, Δfd (1，2) =Δfd (2，3) ≠Δfd (3，1) ), so it is unequally spaced Doppler multiplexing transmission (unequally spaced DDM transmission).

[0236] In addition, Fig.11 In the transmission antenna, the Doppler frequency shift interval between the transmitting antennas Tx#1 and Tx#2 in the beam direction B1 is Δfd (1，2) =Δfd,Δfd (2，1) =3Δfd. Therefore, the number of transmitting antennas N for beam direction B1 is B1 = 2, the intervals of the Doppler frequency shift amounts given to the transmitting antennas are not all the same, but include unequal intervals (Δfd (1，2) ≠Δfd (2，1) ), so it is an unequally spaced Doppler multiplexing transmission (unequally spaced DDM transmission) performed by the transmitting antenna in the beam direction B1.

[0237] In addition, Fig.11 In the example, the number of transmitting antennas in the beam direction B2 is N. B2 =1, which means that the transmission antennas in the beam direction B2 do not form a relationship for Doppler multiplexing transmission.

[0238] therefore, Fig.11 The example shown is a setting example of the pattern of the Doppler shift amount that satisfies condition 2.

[0239] In addition, Fig.11 In, N B1 (=2)≠N B2 (=1). For example, Fig.11 In the example shown, the pattern of the Doppler shift amount assigned to the transmission antenna in the beam direction B1 is different from the pattern of the Doppler shift amount assigned to the transmission antenna in the beam direction B2.

[0240] therefore, Fig.11 The example shown is an example of setting the pattern of the Doppler shift amount that satisfies condition 1 (2).

[0241] The following describes the transmission antenna unit 105 including Fig.11 An example of a received signal in the output of the Doppler analysis unit 209 is described in which the transmitting antennas have beam directions B1 and B2 for setting the Doppler frequency shift amount shown, and the receiving antenna unit 202 is an omnidirectional antenna (or an antenna having a directional characteristic that is approximately uniform within the field of view covered by the two transmitting antennas in beam directions B1 and B2).

[0242] Fig.12 This is an example of the output of the Doppler analysis unit 209 showing a target object reflected wave of a certain distance index. For example, the target object reflected wave includes fd target This Doppler frequency. Fig.12 As shown, the radar device 10 receives Fig.11 The amount of Doppler shift shown occurs based on fdtarget The amount of Doppler shift in the signal.

[0243] in addition, Fig.13 An example of a multi-beam transmission MIMO radar (for example, the radar device 10 ) that forms transmission beams in the beam direction B1 (Tx Beam # 1 ) and the beam direction B2 (Tx Beam # 2 ) is shown.

[0244] For example, in the direction of the object Fig.13 In the case of the target object direction (1) shown in FIG. 1 (for example, when the target object exists around the beam direction B1), the radiation direction of the radar transmission wave transmitted from Tx#1 and Tx#2 in the beam direction B1 coincides with the target object direction. Fig.12 As shown in (a), the reception level of the received signal of the reflected wave from the target object corresponding to Tx#1 and Tx#2 in the radar device 10 is high. Fig.13 In the case of the target direction (1) shown in FIG. 1 , the radiation direction of the radar transmission wave transmitted from Tx#3 in beam direction B2 is inconsistent with the target direction, and the target direction is equivalent to the zero azimuth of the transmission beam B2. Fig.12 As shown in (a), the reception level of the received signal of the reflected wave from the target object corresponding to Tx#3 in the radar device 10 is lower than the reception level of the received signal corresponding to Tx#1 and Tx#2. Fig.12 As shown in (a), the reception level of the reception signal corresponding to Tx#3 is greatly different from the reception levels of the reception signals corresponding to Tx#1 and Tx#2, and may be more than 10dB lower depending on the beam pointing characteristics of the zero azimuth of Tx#3.

[0245] In addition, for example, when the target object direction is the middle direction between the beam direction B1 and the beam direction B2, and the target object direction is the direction of the region where the beam widths of the two beams overlap by about 3 dB or 6 dB (for example, Fig.13 The direction of the object shown in (2)), such as Fig.12 As shown in (b), the reception level of the reception signal corresponding to Tx#1 and Tx#2 in the beam direction B1 is approximately the same as the reception level of the reception signal corresponding to Tx#3 in the beam direction B2.

[0246] In addition, for example, in the direction of the object Fig.13 In the case of the target object direction (3) shown in FIG. 1 (for example, when the target object exists around the beam direction B2), the radiation direction of the radar transmission wave transmitted from Tx#3 in the beam direction B2 coincides with the target object direction. Fig.12As shown in (c), the reception level of the received signal of the reflected wave from the target object corresponding to Tx#3 in the radar device 10 is high. Fig.13 In the case of the target direction (3) shown in FIG. 1 , the radiation direction of the radar transmission wave transmitted from Tx#1 and Tx#2 in beam direction B1 is not consistent with the target direction, and the target direction is equivalent to the zero azimuth of the transmission beam B1. Fig.12 As shown in (c), the reception level of the received signal of the reflected wave corresponding to Tx#1 and Tx#2 in the radar device 10 is lower than the reception level of the received signal corresponding to Tx#3. Fig.12 As shown in (c), the reception level of the reception signal corresponding to Tx#1 and Tx#2 is greatly different from the reception level of the reception signal corresponding to Tx#3, and may be more than 10dB lower depending on the beam pointing characteristics of the zero azimuth of Tx#1 and Tx#2.

[0247] For example, in Fig.12 As shown in (b), the target direction is the center direction between the beam direction B1 and the beam direction B2 ( Fig.13 In the case of the target direction (2) shown in the figure, the radar device 10 receives the reception signals corresponding to the transmission antennas in each beam direction at substantially the same reception level. Therefore, the signals transmitted from the Nt transmission antennas including the transmission antennas in the beam direction B1 and the beam direction B2 are Doppler multiplexed and transmitted using the Doppler frequency shift intervals that become non-uniformly spaced Doppler multiplexing. Therefore, the radar device 10 can demultiplex the Doppler multiplexed signal based on the demultiplexing operation of the existing Doppler multiplexed signal (for example, the demultiplexing operation of the existing Doppler multiplexed signal is disclosed in Patent Documents 6, 7, etc., and this point is also the same in the following embodiments).

[0248] In addition, in Fig.12 As shown in (a), the target direction is the beam direction B1 ( Fig.13 In the case of the object direction (1) shown in FIG. Fig.12 As shown in (c), the target direction is the beam direction B2 ( Fig.13 In the case of the target direction (3) shown in the figure), the radar device 10 receives different Doppler multiplexed signals (for example, the Doppler multiplexed signals satisfying condition 1 (2)) depending on the target direction. Fig.12 (a) Fig.13 In the case of the target direction (1) shown in FIG. 1 , the radar device 10 receives the Doppler frequency shift interval Δfd (1，2) or Δfd (2，1) On the other hand, for example, Fig.12 (c) Fig.13 In the case of the target direction (3) shown in FIG. 1 , the radar device 10 receives a signal of a Doppler frequency component.

[0249] In this way, when the direction of the target object is the beam direction B1 or B2, when the reception level of the reception signal of the transmitting antenna corresponding to the beam direction B1 decreases and when the reception level of the reception signal of the transmitting antenna corresponding to the beam direction B2 decreases, the radar device 10 receives the reflected wave signal containing the Doppler frequency components of different patterns.

[0250] Thus, the radar device 10 can determine, for example, based on the peak value (for example, the number of peaks) of the detected Doppler frequency in the Doppler multiplexing and demultiplexing unit 211 described later whether a decrease in the reception level of the reception signal corresponding to the transmission antenna in the beam direction B1 has occurred (for example, Fig.12 (c) of the state), or the reception level of the received signal corresponding to the transmitting antenna of the beam direction B2 is reduced (for example, Fig.12 state of (a)).

[0251] In addition, for example, for the Doppler multiplexed signals transmitted from the transmission antennas Tx#1 and Tx#2 in the beam direction B1, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that is non-uniformly spaced Doppler multiplexing. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is the received signal of the transmission antennas Tx#1 and Tx#2 corresponding to the beam direction B1, the radar device 10 can demultiplex the Doppler multiplexed signal using the existing demultiplexing operation of the Doppler multiplexed signal.

[0252] In addition, for example, the transmission antenna Tx#3 of the beam direction B2 is a single antenna transmission. Therefore, for example, when the Doppler multiplexing and demultiplexing unit 211 determines that the received signal is a received signal corresponding to the transmission antenna Tx#3 of the beam direction B2, the radar device 10 may not perform the demultiplexing processing of the Doppler multiplexing signal of the received signal of the beam direction B2.

[0253] By operating the Doppler multiplexing and demultiplexing unit 211 in this manner, the radar device 10 can determine the Doppler frequency fd of the target object within the range of -1 / (2Tr)≦fd<1 / (2Tr) and obtain an output in which the transmission antennas are associated with each Doppler multiplexed signal.

[0254] <Doppler shift amount setting example 2>

[0255] Fig.14 Indicates the number of transmitting antennas Nt = 4, N B1 =2,N B2An example of setting the pattern of the Doppler shift amount for the transmission Doppler frequency when =2. Fig.14 , Tx#1 and Tx#2 are respectively transmitting antennas of beam direction B1 (for example, transmitting antennas forming transmit beam B1), and Tx#3 and Tx#4 are respectively transmitting antennas of beam direction B2 (for example, transmitting antennas forming transmit beam B2).

[0256] In addition, in the setting example 2 of the Doppler frequency shift amount, if Fig.14 As shown, the basic unit of the Doppler frequency shift interval in the Doppler frequency shift unit 104 is set to Δfd=1 / (Tr×(N DM +δ))=1 / (5Tr), and δ=1, but the value of δ is not limited to this. δ can be a positive integer or a positive real number.

[0257] exist Fig.14 In the example shown, the first to fourth Doppler shift units 104 (or Doppler shift units 104 - 1 to 104 - 4 ) can perform the following operations.

[0258] For example, in order to provide the Doppler shift amount DOP1 = -1 / (2Tr) to the first transmission antenna Tx#1, the first Doppler shift unit 104 provides a phase rotation of Φ1(m) = -π(m-1) according to the transmission period Tr of the chirp signal and outputs it.

[0259] For example, in order to provide the Doppler shift amount DOP2 = -3 / (10Tr) to the second transmission antenna Tx#2, the second Doppler shift unit 104 provides a phase rotation of Φ2(m) = -3π(m-1) / 5 according to the transmission period Tr of the chirp signal and outputs it.

[0260] For example, in order to provide the Doppler shift amount DOP3 = -1 / (10Tr) to the third transmission antenna Tx#3, the third Doppler shift unit 104 provides a phase rotation of Φ3(m) = -π(m-1) / 5 according to the transmission period Tr of the chirp signal and outputs it.

[0261] For example, in order to provide the Doppler shift amount DOP4=3 / (10Tr) to the fourth transmission antenna Tx#4, the fourth Doppler shift unit 104 provides a phase rotation of Φ4(m)=3π(m-1) / 5 according to the transmission period Tr of the chirp signal and outputs it.

[0262] Hereinafter, the interval between the Doppler frequency shift amounts given to Tx#n1 and Tx#n2 is expressed as the Doppler frequency shift interval “Δfd (n1，n2) ”.

[0263] exist Fig.14 In the example, the interval (Doppler shift interval) of the Doppler frequency shift amount given to each transmitting antenna Tx#1 to Tx#4 is Δfd(1，2) =Δfd,Δfd (2，3) =Δfd,Δfd (3，4) =2Δfd,Δfd (4，1) =Δfd. Therefore, Fig.14 In the example, the intervals of the Doppler frequency shift amounts given to the respective transmitting antennas when the number of transmitting antennas Nt=4 are not all the same, but include unequal intervals (for example, Δfd (1，2) =Δfd (2，3) =Δfd (4，1) ≠Δfd (3，4) ), so it is unequally spaced Doppler multiplexing transmission (unequally spaced DDM transmission).

[0264] In addition, Fig.14 In the transmission antenna, the interval of the Doppler frequency shift between the transmitting antennas Tx#1 and Tx#2 in the beam direction B1 is Δfd (1，2) =Δfd,Δfd (2，1) =4Δfd. Therefore, the number of transmitting antennas N for beam direction B1 is B1 = 2, the intervals of the Doppler frequency shift amounts given to the transmitting antennas are not all the same, but include unequal intervals (Δfd (1，2) ≠Δfd (2，1) ), so it is an unequally spaced Doppler multiplexing transmission (unequally spaced DDM transmission) performed by the transmitting antenna in the beam direction B1.

[0265] In addition, Fig.14 In the example, the interval of the Doppler frequency shift between the transmitting antennas Tx#3 and Tx#4 in the beam direction B2 is Δfd (3，4) =2Δfd,Δfd (4，3) =3Δfd. Therefore, the number of transmitting antennas N for beam direction B2 is B2 = 2, the intervals of the Doppler frequency shift amounts given to the transmitting antennas are not all the same, but include unequal intervals (Δfd (3，4) ≠Δfd (4，3) ), so it is an unequally spaced Doppler multiplexing transmission (non-equally spaced DDM transmission) performed by the transmitting antenna in the beam direction B2.

[0266] therefore, Fig.14 The example shown is a setting example of the pattern of the Doppler shift amount that satisfies condition 2.

[0267] In addition, Fig.14 The interval of the Doppler frequency shift between the transmitting antennas Tx#1 and Tx#2 in the beam direction B1 is Δfd (1，2) =Δfd,Δfd (2，1)=4Δfd, the interval of the Doppler frequency shift between the transmitting antennas Tx#3 and Tx#4 in the beam direction B2 is Δfd (3，4) =2Δfd,Δfd (4，3) =3Δfd. Therefore, the Doppler shift amount between the transmission antennas Tx#1 and Tx#2 in the beam direction B1 and the Doppler shift amount between the transmission antennas Tx#3 and Tx#4 in the beam direction B2 include different Doppler shift intervals.

[0268] For example, the maximum DDM interval of the Doppler frequency shift between the transmitting antennas Tx#1 and Tx#2 in the beam direction B1 is Δfd (2，1) =4Δfd, the maximum DDM interval of the Doppler frequency shift between the transmitting antennas Tx#3 and Tx#4 in the beam direction B2 is Δfd (4，3) =3Δfd, which are different from each other. Similarly, for example, the minimum DDM interval of the Doppler frequency shift between the transmitting antennas Tx#1 and Tx#2 in the beam direction B1 is Δfd (1，2) =Δfd, the minimum DDM interval of the Doppler frequency shift between the transmitting antennas Tx#3 and Tx#4 in beam direction B2 is Δfd (3，4) =2Δfd, the two are different.

[0269] As mentioned above, in Fig.14 In the example shown, the Doppler multiplexing number N of the transmitting antennas Tx#1 and Tx#2 based on the beam direction B1 is B1 The Doppler multiplexing number N with the transmitting antennas Tx#3 and Tx#4 based on the beam direction B2 B2 The transmission antennas Tx#1 and Tx#2 in beam direction B1 and the transmission antennas Tx#3 and Tx#4 in beam direction B2 have the same pattern (for example, Doppler shift interval) of the Doppler shift amounts allocated to them respectively.

[0270] therefore, Fig.14 The example shown is an example of setting the pattern of the Doppler shift amount that satisfies condition 1 (1).

[0271] The following describes the transmission antenna unit 105 including Fig.14 An example of a received signal in the output of the Doppler analysis unit 209 is described in which the Doppler frequency shift amount is set as shown, the transmitting antennas have different beam directions of beam directions B1 and B2, and the receiving antenna unit 202 is an omnidirectional antenna (or an antenna having a directional characteristic that is approximately uniform within the field of view covered by the two transmitting antennas in beam directions B1 and B2).

[0272] Fig.15This is an example of the output of the Doppler analysis unit 209 showing a target object reflected wave of a certain distance index. For example, the target object reflected wave includes fd target This Doppler frequency. Fig.15 As shown, the radar device 10 receives Fig.14 The amount of Doppler shift shown occurs based on fd target The amount of Doppler shift in the signal.

[0273] In addition, in setting example 2, Fig.13 Similarly, an example of a multi-beam transmission MIMO radar (for example, radar device 10 ) that forms transmission beams in beam direction B1 (Tx Beam # 1 ) and beam direction B2 (Tx Beam # 2 ) will be described.

[0274] For example, in the direction of the object Fig.13 In the case of the target object direction (1) shown in FIG. 1 (for example, when the target object exists around the beam direction B1), the radiation direction of the radar transmission wave transmitted from Tx#1 and Tx#2 in the beam direction B1 coincides with the target object direction. Fig.15 As shown in (a), the reception level of the received signal of the reflected wave from the target object corresponding to Tx#1 and Tx#2 in the radar device 10 is high. Fig.13 In the case of the target direction (1) shown in FIG. 1 , the radiation direction of the radar transmission wave transmitted from Tx#3 and Tx#4 in beam direction B2 is not consistent with the target direction, and the target direction is equivalent to the zero azimuth of the transmission beam B2. Fig.15 As shown in (a), the reception level of the received signal of the reflected wave from the target corresponding to Tx#3 and Tx#4 in the radar device 10 is lower than the reception level of the received signal corresponding to Tx#1 and Tx#2. Fig.15 As shown in (a), the reception level of the reception signal corresponding to Tx#3 and Tx#4 is greatly different from the reception level of the reception signal corresponding to Tx#1 and Tx#2, and depends on the beam pointing characteristics of the zero azimuth of Tx#3 and Tx#4, and may be, for example, 10 dB or more lower.

[0275] In addition, for example, when the target object direction is the middle direction between the beam direction B1 and the beam direction B2, and the target object direction is the direction of the region where the beam widths of the two beams overlap by about 3 dB or 6 dB (for example, Fig.13 The direction of the object shown in (2)), such as Fig.15 As shown in (b), the reception level of the reception signal corresponding to Tx#1 and Tx#2 in the beam direction B1 is about the same as the reception level of the reception signal corresponding to Tx#3 and Tx#4 in the beam direction B2.

[0276] In addition, for example, in the direction of the object Fig.13 In the case of the target object direction (3) shown in FIG. 1 , the radiation direction of the radar transmission wave transmitted from Tx#3 and Tx#4 in the beam direction B2 is consistent with the target object direction. Fig.15 As shown in (c), the reception level of the received signal of the reflected wave from the target object corresponding to Tx#3 and Tx#4 in the radar device 10 is high. Fig.13 In the case of the target direction (3) shown in FIG. 1 , the radiation direction of the radar transmission wave transmitted from Tx#1 and Tx#2 in beam direction B1 is not consistent with the target direction, and the target direction is equivalent to the zero azimuth of the transmission beam B1. Fig.15 As shown in (c), the reception level of the received signal of the reflected wave corresponding to Tx#1 and Tx#2 in the radar device 10 is lower than the reception level of the received signal corresponding to Tx#3 and Tx#4. Fig.15 As shown in (c), the reception level of the reception signal corresponding to Tx#1 and Tx#2 is greatly different from the reception level of the reception signal corresponding to Tx#3 and Tx#4, and depends on the beam pointing characteristics of the zero azimuth of Tx#1 and Tx#2, and may be, for example, 10 dB or more lower.

[0277] For example, in Fig.15 As shown in (b), the target direction is the center direction between the beam direction B1 and the beam direction B2 ( Fig.13 In the case of the target direction (2) shown in FIG. 1 ), the radar device 10 receives the reception signals corresponding to the transmission antennas in each beam direction at substantially the same reception level. Therefore, the signals transmitted from the Nt transmission antennas including the transmission antennas in the beam direction B1 and the beam direction B2 are Doppler multiplexed and transmitted using the Doppler frequency shift intervals that become non-uniformly spaced Doppler multiplexing. Therefore, the radar device 10 can demultiplex the Doppler multiplexed signal based on the existing demultiplexing operation of the Doppler multiplexed signal.

[0278] In addition, in Fig.15 As shown in (a), the target direction is the beam direction B1 ( Fig.13 In the case of the object direction (1) shown in FIG. Fig.15 As shown in (c), the target direction is the beam direction B2 ( Fig.13 In the case of the target direction (3) shown in the figure), the radar device 10 receives different Doppler multiplexed signals (for example, the Doppler multiplexed signals satisfying condition 1 (1)) depending on the target direction. Fig.15 (a) Fig.13 In the case of the target direction (1) shown in FIG. 1 , the radar device 10 receives the Doppler frequency shift interval Δfd(1，2) or Δfd (2，1) On the other hand, for example, Fig.15 (c) Fig.13 In the case of the target direction (3) shown in FIG. 1 , the radar device 10 receives the Doppler frequency shift interval Δfd (3，4) or Δfd (4，3) The signal of the two Doppler frequency components.

[0279] In this way, when the direction of the target object is the beam direction B1 or B2, when the reception level of the reception signal of the transmitting antenna corresponding to the beam direction B1 decreases and when the reception level of the reception signal of the transmitting antenna corresponding to the beam direction B2 decreases, the radar device 10 receives the reflected wave signal containing the Doppler frequency components of different patterns.

[0280] Thus, the radar device 10 can determine, for example, based on the peak value (for example, the interval between the peaks) of the detected Doppler frequency in the Doppler multiplexing and demultiplexing unit 211 described later whether a decrease in the reception level of the reception signal corresponding to the transmission antenna in the beam direction B1 has occurred (for example, Fig.15 (c) of the state), or the reception level of the received signal corresponding to the transmitting antenna of the beam direction B2 is reduced (for example, Fig.15 state of (a)).

[0281] In addition, for example, for the Doppler multiplexed signals transmitted from the transmission antennas Tx#1 and Tx#2 in the beam direction B1, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that is non-uniformly spaced Doppler multiplexing. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is the received signal of the transmission antennas Tx#1 and Tx#2 corresponding to the beam direction B1, the radar device 10 can demultiplex the Doppler multiplexed signal using the existing demultiplexing operation of the Doppler multiplexed signal.

[0282] Similarly, for example, for the Doppler multiplexed signals transmitted from the transmission antennas Tx#3 and Tx#4 in the beam direction B2, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that is non-uniformly spaced Doppler multiplexing. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is the received signal of the transmission antennas Tx#3 and Tx#4 corresponding to the beam direction B2, the radar device 10 can demultiplex the Doppler multiplexed signal using the existing demultiplexing operation of the Doppler multiplexed signal.

[0283] By operating the Doppler multiplexing and demultiplexing unit 211 in this manner, the radar device 10 can determine the Doppler frequency fd of the target object within the range of -1 / (2Tr)≦fd<1 / (2Tr) and obtain an output in which the transmission antennas are associated with each Doppler multiplexed signal.

[0284] In the above, the setting examples 1 and 2 of the Doppler frequency shift amount are described. Hereinafter, different Doppler setting examples are described.

[0285] <Doppler shift amount setting example 3>

[0286] Fig.16 Indicates the number of transmitting antennas Nt = 3, N B1 =2,N B2 =1 is an example of setting the pattern of the Doppler shift amount for the transmission Doppler frequency. Fig.16 , Tx#1 and Tx#2 are respectively the transmitting antennas of the beam direction B1 (for example, the transmitting antennas forming the transmitting beam B1), and Tx#3 is the transmitting antenna of the beam direction B2 (for example, the transmitting antennas forming the transmitting beam B2).

[0287] In addition, in the setting example 3 of the Doppler frequency shift amount, Fig.16 As shown, the basic unit of the Doppler frequency shift interval in the Doppler frequency shift unit 104 is set to Δfd=1 / (Tr×(N DM +δ))=1 / (4Tr), and δ=1, but the value of δ is not limited to this. δ can be a positive integer or a positive real number.

[0288] exist Fig.16 In the example shown, the first to third Doppler shift units 104 (or Doppler shift units 104 - 1 to 104 - 3 ) can perform the following operations.

[0289] For example, in order to give the Doppler shift amount DOP1=-1 / (2Tr) to the first transmitting antenna Tx#1, the first Doppler shift unit 104 gives a phase rotation of Φ1(m)=2πDOP1×(m-1)Tr=-π(m-1) according to the transmission period Tr of the chirp signal and outputs it.

[0290] For example, in order to give the Doppler shift amount DOP2=0 to the second transmission antenna Tx#2, the second Doppler shift unit 104 gives a phase rotation of Φ2(m)==2πDOP2×(m-1)Tr=0 according to the transmission period Tr of the chirp signal and outputs it.

[0291] For example, in order to give the third transmitting antenna Tx#3 a Doppler shift amount DOP3=-1 / (4Tr), the third Doppler frequency shift unit 104 gives a phase rotation Φ3(m)=2πDOP3×(m-1)Tr=-π(m-1) / 2 according to the transmission period Tr of the chirp signal and outputs it.

[0292] Hereinafter, the interval between the Doppler frequency shift amounts given to Tx#n1 and Tx#n2 is expressed as the Doppler frequency shift interval “Δfd (n1，n2) ”.

[0293] exist Fig.16 In the example, the interval (Doppler shift interval) of the Doppler frequency shift amount given to each transmission antenna Tx#1 to Tx#3 is Δfd (1，3) =Δfd (3，2) =Δfd,Δfd (2，1) =2Δfd. Therefore, Fig.16 In the example, the intervals of the Doppler frequency shift amounts given to the respective transmitting antennas when the number of transmitting antennas Nt=3 are not all the same, but include unequal intervals (for example, Δfd (1，3) =Δfd (3，2) ≠Δfd (2，1) ), so it is unequally spaced Doppler multiplexing transmission (unequally spaced DDM transmission).

[0294] In addition, Fig.16 In the transmission antenna, the interval of the Doppler frequency shift between the transmitting antennas Tx#1 and Tx#2 in the beam direction B1 is Δfd (1，2) =2Δfd,Δfd (2，1) =2Δfd. Therefore, the number of transmitting antennas N for beam direction B1 is B1 = 2, the intervals of the Doppler shift amounts given to the respective transmitting antennas are all the same, which is equal-interval Doppler multiplexing transmission (equal-interval DDM transmission).

[0295] In addition, Fig.16 In the example, the number of transmitting antennas in the beam direction B2 is N. B2 =1, which means that the transmission antennas in the beam direction B2 do not form a relationship for Doppler multiplexing transmission.

[0296] In addition, Fig.16 In, N B1 (=2)≠N B2 (=1). For example, Fig.16 In the example shown, the pattern of the Doppler shift amount assigned to the transmission antenna in the beam direction B1 is different from the pattern of the Doppler shift amount assigned to the transmission antenna in the beam direction B2.

[0297] therefore, Fig.16 The example shown is an example of setting the pattern of the Doppler shift amount that satisfies (2) of condition 1 but does not satisfy condition 2.

[0298] For example, in the direction of the target object, the beam direction B1 (for example, Fig.13 In the case where the target direction is (1) as shown) and the target direction is the beam direction B2 (for example, Fig.13 In the case of the target object direction (3) shown in the figure, the radar device 10 receives different Doppler multiplexed signals (for example, the Doppler multiplexed signals satisfying condition 1 (2)) depending on the target object direction, as in setting example 1. Thus, the radar device 10 can, for example, determine in the Doppler multiplexing and demultiplexing unit 211 described later whether a decrease in the reception level of the received signal corresponding to the transmitting antenna in the beam direction B1 or a decrease in the reception level of the received signal corresponding to the transmitting antenna in the beam direction B2 has occurred based on the peak value of the detected Doppler frequency (for example, the number of peaks).

[0299] In addition, for example, the Doppler multiplexed signals transmitted from the transmission antennas Tx#1 and Tx#2 in the beam direction B1 are Doppler multiplexed and transmitted using the Doppler frequency shift interval that does not satisfy the condition 2 and is an equally spaced Doppler multiplexed signal. Therefore, for example, when the Doppler multiplex demultiplexing unit 211 determines that the received signal is a received signal corresponding to the transmission antenna in the beam direction B1, the radar device 10 can demultiplex the Doppler multiplexed signal using the existing demultiplexing operation of the Doppler multiplexed signal. In this case, the radar device 10 can determine the Doppler frequency fd of the target object in the range of -1 / (4Tr)≦fd<1 / (4Tr), and can obtain an output that matches the transmission antenna to each Doppler multiplexed signal.

[0300] In addition, for example, the transmitting antenna Tx#3 in the beam direction B2 is a single antenna transmission. Therefore, for example, when the Doppler multiplexing and demultiplexing unit 211 determines that the received signal is a received signal corresponding to the transmitting antenna Tx#3 in the beam direction B2, the radar device 10 may not perform demultiplexing processing on the Doppler multiplexing signal of the received signal in the beam direction B2. Through the operation of the Doppler multiplexing and demultiplexing unit 211, the radar device 10 can determine the Doppler frequency fd of the target object in the range of -1 / (2Tr)≦fd<1 / (2Tr), and can obtain an output that corresponds to the transmitting antenna for each Doppler multiplexing signal.

[0301] <Doppler shift amount setting example 4>

[0302] Fig.17 Indicates the number of transmitting antennas Nt = 6, N B1 =3, N B2An example of setting the pattern of the Doppler shift amount for the transmission Doppler frequency when =3. Fig.17 , Tx#1, Tx#2, and Tx#4 are respectively transmitting antennas of beam direction B1 (e.g., transmitting antennas forming transmit beam B1), and Tx#3, Tx#5, and Tx#6 are respectively transmitting antennas of beam direction B2 (e.g., transmitting antennas forming transmit beam B2).

[0303] In addition, in the setting example 4 of the Doppler frequency shift amount, Fig.17 As shown, the basic unit of the Doppler frequency shift interval in the Doppler frequency shift unit 104 is set to Δfd=1 / (Tr×(N DM +δ))=1 / (8Tr), and δ=2, but the value of δ is not limited to this. δ can be a positive integer or a positive real number.

[0304] exist Fig.17 In the example shown, the first to sixth Doppler shift units 104 (or Doppler shift units 104 - 1 to 104 - 6 ) can perform the following operations.

[0305] For example, in order to provide the Doppler shift amount DOP1 = -1 / (2Tr) to the first transmission antenna Tx#1, the first Doppler shift unit 104 provides a phase rotation of Φ1(m) = -π(m-1) according to the transmission period Tr of the chirp signal and outputs it.

[0306] For example, in order to provide the Doppler shift amount DOP2 = -3 / (8Tr) to the second transmission antenna Tx#2, the second Doppler shift unit 104 provides a phase rotation of Φ2(m) = -3π(m-1) / 4 according to the transmission period Tr of the chirp signal and outputs it.

[0307] For example, in order to provide the Doppler shift amount DOP3 = -1 / (4Tr) to the third transmission antenna Tx#3, the third Doppler shift unit 104 provides a phase rotation of Φ3(m) = -π(m-1) / 2 according to the transmission period Tr of the chirp signal and outputs it.

[0308] For example, in order to provide the Doppler shift amount DOP4 = -1 / (8Tr) to the fourth transmission antenna Tx#4, the fourth Doppler shift unit 104 provides a phase rotation of Φ4(m) = -π(m-1) / 4 according to the transmission period Tr of the chirp signal and outputs it.

[0309] For example, in order to give the Doppler shift amount DOP5 = 0 to the fifth transmission antenna Tx# 5 , the fifth Doppler shift unit 104 gives a phase rotation Φ5(m) = 0 according to the transmission period Tr of the chirp signal and outputs it.

[0310] For example, in order to provide the Doppler shift amount DOP6=1 / (8Tr) to the sixth transmission antenna Tx#6, the sixth Doppler shift unit 104 provides a phase rotation of Φ6(m)=π(m-1) / 4 according to the transmission period Tr of the chirp signal and outputs it.

[0311] Hereinafter, the interval between the Doppler frequency shift amounts given to Tx#n1 and Tx#n2 is expressed as the Doppler frequency shift interval “Δfd (n1，n2) ”.

[0312] exist Fig.17 In the example, the interval (Doppler shift interval) of the Doppler frequency shift amount given to each transmission antenna Tx#1 to Tx#6 is Δfd (1，2) =Δfd (2，3) =Δfd (3，4) =Δfd (4，5) =Δfd (5，6) =Δfd,Δfd (6，1) =3Δfd. Therefore, Fig.17 In the example, the intervals of the Doppler frequency shift amounts given to the respective transmitting antennas of the number of transmitting antennas Nt=6 are not all the same, but include unequal intervals (for example, Δfd (1，2) =Δfd (2，3) =Δfd (3，4) =Δfd (4，5) =Δfd (5，6) ≠Δfd (6，1) ), so it is unequally spaced Doppler multiplexing transmission (unequally spaced DDM transmission).

[0313] In addition, Fig.17 In the transmission antenna, the interval of the Doppler frequency shift between the transmitting antennas Tx#1, Tx#2, and Tx#4 in the beam direction B1 is Δfd (1，2) =Δfd,Δfd (2，4) =2Δfd,Δfd (4，1) =5Δfd. Therefore, the number of transmitting antennas N for beam direction B1 is B1 = 3, the intervals of the Doppler frequency shift amounts given to the transmitting antennas are not all the same, but include unequal intervals (Δfd (1，2) ≠Δfd (2，4) =Δfd (4，1) ), so it is an unequally spaced Doppler multiplexing transmission (non-equally spaced DDM transmission) performed by the transmitting antenna in the beam direction B1.

[0314] In addition, Fig.17 In the transmission antenna, the interval of the Doppler frequency shift between the transmitting antennas Tx#3, Tx#5, and Tx#6 in the beam direction B2 is Δfd (3，5) =2Δfd,Δfd(5，6) =Δfd,Δfd (6，3) =5Δfd. Therefore, the number of transmitting antennas N for beam direction B2 is B2 = 3, the intervals of the Doppler frequency shift amounts given to the transmitting antennas are not all the same, but include unequal intervals (Δfd (3，5) ≠Δfd (5，6) ≠Δfd (6，3) ), so it is an unequally spaced Doppler multiplexing transmission (non-equally spaced DDM transmission) performed by the transmitting antenna in the beam direction B2.

[0315] therefore, Fig.17 The example shown is a setting example of the pattern of the Doppler shift amount that satisfies condition 2.

[0316] In addition, Fig.17 The Doppler frequency shift between the transmitting antennas Tx#1, Tx#2, and Tx#4 in the beam direction B1 is Δfd (1，2) =Δfd,Δfd (2，4) =2Δfd,Δfd (4，1) =5Δfd, the Doppler frequency shift between the transmitting antennas Tx#3, Tx#5, and Tx#6 in beam direction B2 is Δfd (3，5) =2Δfd,Δfd (5，6) =Δfd,Δfd (6，3) =5Δfd. As mentioned above, Fig.17 In the example, the Doppler multiplexing number N of the transmitting antennas Tx#1, Tx#2, and Tx#4 based on the beam direction B1 is B1 The Doppler multiplexing number N with the transmitting antennas Tx#3, Tx#5, and Tx#6 based on the beam direction B2 B2 In addition, Fig.17 , the Doppler frequency shift amounts between the transmitting antennas Tx#1, Tx#2, and Tx#4 in beam direction B1 and the Doppler frequency shift amounts between the transmitting antennas Tx#3, Tx#5, and Tx#6 in beam direction B2 include the same combination of Doppler frequency shift intervals, but the order of the Doppler frequency shift intervals between the beam direction B1 and the beam direction B2 on the Doppler frequency axis is different.

[0317] For example, in Fig.17 In , the order of the intervals of the Doppler frequency shift amounts assigned to the transmitting antennas Tx#1, Tx#2, and Tx#4 in the beam direction B1 is Δfd, 2Δfd, and 5Δfd. Fig.17 In the example, the order of the intervals of the Doppler frequency shift amounts assigned to the transmitting antennas Tx#3, Tx#5, and Tx#6 in the beam direction B2 is 2Δfd, Δfd, and 5Δfd. Fig.17In FIG. 1 , although the transmitting antennas in beam direction B1 and beam direction B2 contain the same combination of Doppler frequency shift intervals (e.g., Δfd, 2Δfd, 5Δfd), the order of these intervals is different between different beam directions. Fig.17 For example, even if the Doppler shift interval between the transmitting antennas in the beam direction B1 and the Doppler shift interval between the transmitting antennas in the beam direction B2 are cyclically shifted on the Doppler frequency axis, the Doppler shift amounts will not be consistent between the different beam directions.

[0318] As mentioned above, in Fig.17 In the example shown, the pattern of Doppler shift amounts assigned to the transmitting antennas Tx#1, Tx#2, and Tx#4 in the beam direction B1 is different from the pattern of Doppler shift amounts assigned to the transmitting antennas Tx#3, Tx#5, and Tx#6 in the beam direction B2.

[0319] therefore, Fig.17 The example shown is an example of setting the pattern of the Doppler shift amount that satisfies condition 1 (3).

[0320] The following describes the transmission antenna unit 105 including Fig.17 An example of a received signal in the output of the Doppler analysis unit 209 is described in which the Doppler frequency shift amount is set as shown, the transmitting antennas have different beam directions of beam directions B1 and B2, and the receiving antenna unit 202 is an omnidirectional antenna (or an antenna having a directional characteristic that is approximately uniform within the field of view covered by the two transmitting antennas in beam directions B1 and B2).

[0321] In addition, in setting example 4, Fig.13 Similarly, an example of a multi-beam transmission MIMO radar (for example, radar device 10 ) that forms transmission beams in beam direction B1 (Tx Beam # 1 ) and beam direction B2 (Tx Beam # 2 ) will be described.

[0322] For example, in the direction of the object Fig.13 In the case of the target object direction (1) shown in FIG. 1 (for example, when the target object exists in the vicinity of the beam direction B1), the radiation direction of the radar transmission wave transmitted from Tx#1, Tx#2, and Tx#4 in the beam direction B1 coincides with the target object direction. Therefore, the reception level of the reception signal of the reflected wave from the target object corresponding to Tx#1, Tx#2, and Tx#4 in the radar device 10 is high. On the other hand, in the case of the target object direction Fig.13In the case of the target object direction (1) shown in the figure, the radiation direction of the radar transmission wave transmitted from Tx#3, Tx#5 and Tx#6 of the beam direction B2 does not coincide with the target object direction, and the target object direction corresponds to the zero azimuth of the transmission beam B2. Therefore, the reception level of the reception signal of the reflected wave from the target object corresponding to Tx#3, Tx#5 and Tx#6 in the radar device 10 is lower than the reception level of the reception signal corresponding to Tx#1, Tx#2 and Tx#4. The reception level of the reception signal corresponding to Tx#3, Tx#5 and Tx#6 is greatly different from the reception level of the reception signal corresponding to Tx#1, Tx#2 and Tx#4, and may be, for example, 10 dB or more lower depending on the beam directivity characteristics of the zero azimuth of Tx#3, Tx#5 and Tx#6.

[0323] In addition, for example, in the direction of the object Fig.13 In the case of the target object direction (3) shown in FIG. 1 (for example, when the target object exists in the vicinity of the beam direction B2), the radiation direction of the radar transmission wave transmitted from Tx#3, Tx#5, and Tx#6 in the beam direction B2 coincides with the target object direction. Therefore, the reception level of the reception signal of the reflected wave from the target object corresponding to Tx#3, Tx#5, and Tx#6 in the radar device 10 is high. On the other hand, in the case of the target object direction Fig.13 In the case of the target object direction (3) shown in the figure, the radiation direction of the radar transmission wave transmitted from Tx#1, Tx#2 and Tx#4 in the beam direction B1 does not coincide with the target object direction, and the target object direction corresponds to the zero azimuth of the transmission beam B1. Therefore, the reception level of the reception signal corresponding to Tx#1, Tx#2 and Tx#4 in the radar device 10 is lower than the reception level of the reception signal of the reflected wave from the target object corresponding to Tx#3, Tx#5 and Tx#6. For example, the reception level of the reception signal corresponding to Tx#1, Tx#2 and Tx#4 is greatly different from the reception level of the reception signal corresponding to Tx#3, Tx#5 and Tx#6, and it may be, for example, 10 dB or more lower depending on the beam directivity characteristics of the zero azimuth of Tx#1, Tx#2 and Tx#4.

[0324] Thus, the target direction is the beam direction B1 (for example, Fig.13 In the case where the target direction is (1) as shown) and the target direction is the beam direction B2 (for example, Fig.13In the case of the target object direction (3) shown in the condition 1), the radar device 10 receives different Doppler multiplexed signals (for example, Doppler multiplexed signals satisfying condition 1 (3)) depending on the target object direction. Therefore, when the target object direction is the beam direction B1 or B2, when the reception level of the reception signal of the transmission antenna corresponding to the beam direction B1 decreases and when the reception level of the reception signal of the transmission antenna corresponding to the beam direction B2 decreases, the radar device 10 receives reflected wave signals containing Doppler frequency components of different patterns.

[0325] As a result, the radar device 10 can, for example, determine in the Doppler multiplexing and demultiplexing unit 211 described later whether a reduction in the reception level of the reception signal of the transmitting antenna corresponding to the beam direction B1 or a reduction in the reception level of the reception signal of the transmitting antenna corresponding to the beam direction B2 occurs based on the detected Doppler frequency peak value (for example, the order of the intervals between the peak values).

[0326] For example, for the Doppler multiplexed signals transmitted from the transmission antennas Tx#1, Tx#2, and Tx#4 in the beam direction B1, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that is non-uniformly spaced Doppler multiplexing. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is the received signal of the transmission antennas Tx#1, Tx#2, and Tx#4 corresponding to the beam direction B1, the radar device 10 can demultiplex the Doppler multiplexed signal using the existing demultiplexing operation of the Doppler multiplexed signal.

[0327] Similarly, for example, for the Doppler multiplexed signals transmitted from the transmission antennas Tx#3, Tx#5, and Tx#6 in the beam direction B2, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that is non-uniformly spaced Doppler multiplexing. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is the received signal of the transmission antennas Tx#3, Tx#5, and Tx#6 corresponding to the beam direction B2, the radar device 10 can demultiplex the Doppler multiplexed signal using the existing demultiplexing operation of the Doppler multiplexed signal.

[0328] On the other hand, for example, when the target object direction is the middle direction between the beam direction B1 and the beam direction B2, and the target object direction is in the direction of the region where the beam widths of the two beams overlap by about 3 dB or 6 dB (for example, in the case of Fig.13 In the case of the target object direction (2) shown in the figure), the reception levels of the reception signals corresponding to Tx#1, Tx#2, and Tx#4 in the beam direction B1 and the reception levels of the reception signals corresponding to Tx#3, Tx#5, and Tx#6 in the beam direction B2 are about the same. Therefore, in the case where the target object direction is the middle direction between the beam directions B1 and B2 ( Fig.13 In the case of the target direction (2) shown in FIG. 1 ), the radar device 10 receives the reception signals corresponding to the transmission antennas in each beam direction at substantially the same reception level. Therefore, the signals transmitted from the Nt transmission antennas including the transmission antennas in the beam direction B1 and the beam direction B2 are Doppler multiplexed and transmitted using the Doppler frequency shift intervals that become non-uniformly spaced Doppler multiplexing. Therefore, the radar device 10 can demultiplex the Doppler multiplexed signal based on the existing demultiplexing operation of the Doppler multiplexed signal.

[0329] By operating the Doppler multiplexing and demultiplexing unit 211 in this manner, the radar device 10 can determine the Doppler frequency fd of the target object within the range of -1 / (2Tr)≦fd<1 / (2Tr) and obtain an output in which the transmission antennas are associated with each Doppler multiplexed signal.

[0330] In the above, an example of setting the Doppler shift amount has been described.

[0331] The setting of the Doppler shift amount is not limited to the above-mentioned setting examples 1 to 4. For example, the number of transmission antennas Nt (or the number of Doppler multiplexing), the number of transmission antennas N in the beam direction B1, B1 , the number of transmitting antennas N in beam direction B2 B2 At least one of and the Doppler shift interval is other value.

[0332] In addition, the Doppler frequency shift unit 104 gives the Doppler frequency shift amount DOP to the radar transmission signal transmitted from the Nt transmission antennas. n The phase rotation Φ n (m) can be expressed as shown in the following formula (4).

[0333] [Formula 4]

[0334] φ n (m)=(2πT r ×DOP n +Δφ0)(m-1)+φ0 (4)

[0335] Here, Φ0 is the initial phase and ΔΦ0 is the reference Doppler shift phase.

[0336] For example, when Doppler multiplexing transmission is performed using the number of transmission antennas Nt=3, the first Doppler frequency shift unit 104 applies a phase rotation Φ1(m) to the radar transmission signal (e.g., chirp signal) input from the radar transmission signal generation unit 101 according to the transmission period Tr as shown in the following equation (5). The output of the first Doppler frequency shift unit 104 is output from the first transmission antenna (Tx#1), ​​for example. Here, cp(t) represents the chirp signal of each transmission period.

[0337] [Formula 5]

[0338] exp{jφ1(1)}cp(t), exp{jφ1(2)}cp(t),..., exp{jφ1(N c )}cp(t)(5)

[0339] In addition, for example, the second Doppler frequency shift unit 104 applies a phase rotation Φ2(m) to the radar transmission signal (for example, chirp signal) input from the radar transmission signal generation unit 101 according to the transmission period Tr as shown in the following equation (6). The output of the second Doppler frequency shift unit 104 is output from the second transmission antenna (Tx#2), for example.

[0340] [Formula 6]

[0341] exp{jφ2(1)}cp(t), exp{jφ2(2)}cp(t),..., exp{jφ2(N c )}cp(t)(6)

[0342] Similarly, for example, the third Doppler frequency shift unit 104 applies a phase rotation Φ3(m) to the radar transmission signal (for example, chirp signal) input from the radar transmission signal generation unit 101 according to the transmission period Tr as shown in the following equation (7). The output of the third Doppler frequency shift unit 104 is output from the third transmission antenna (Tx#3), for example.

[0343] [Formula 7]

[0344] exp{jφ3(1)}cp(t), exp{jφ3(2)}cp(t),..., exp{jφ3(N c )}cp(t)(7)

[0345] In the above, an example of setting the Doppler shift amount has been described.

[0346] Next, an operation example of the CFAR unit 210 and the Doppler multiplexing / demultiplexing unit 211 corresponding to the operation of the Doppler frequency shift unit 104 described above will be described.

[0347] [Operation Example of CFAR Unit 210]

[0348] For example, in order to receive a reflected wave signal in response to a radar transmission signal from the radar transmission unit 100 , the CFAR unit 210 may perform the following operation example 1 or operation example 2.

[0349] In addition, in the following description, an operation example of the CFAR unit 210 is described in the case where the plurality of receiving antennas of the receiving antenna unit 202 are omnidirectional antennas (or antennas having a directivity characteristic that is substantially uniform within the field of view angles covered by the transmitting antennas in a plurality of different beam directions).

[0350] <Operation Example 1 of CFAR Unit 210>

[0351] In Operation Example 1, an operation example of the CFAR unit 210 is described in the case where, in the Doppler shift unit 104, the value of δ shown in Equation (3) is set to a positive integer.

[0352] In this case, as the interval of the Doppler shift amount assigned to the Doppler multiplexed signal, an interval of Δfd or an integer multiple of Δfd is used. Therefore, each signal subjected to Doppler multiplexing can be detected as being aliased at intervals of Δfd in the Doppler frequency domain output of the Doppler analysis unit 209. Utilizing such a property, for example, the operation of the CFAR unit 210 can be simplified as follows.

[0353] The CFAR unit 210, for example, uses a threshold value for the power sum value obtained by adding the received powers of the reflected wave signals in each of the following ranges, and detects the Doppler peak. The range is the range that is the unit of each interval of the Doppler shift amounts respectively assigned to the radar transmission signals in the Doppler frequency range that is the object of CFAR processing in the output of the Doppler analysis unit 209 (for example, the range of Δfd).

[0354] For example, the CFAR unit 210 calculates, for the outputs of the Doppler analysis units 209 of the first to Na-th signal processing units 206, as shown in Equation (8), the power sum value PowerDDM(f Δfd ), f b ), obtained by adding the power values PowerqFT(f s ) at intervals of Δfd (for example, corresponding to N b ), f sddm ), and performs CFAR processing.

[0355] [Equation 8]

[0356]

[0357] [Equation 9]

[0358]

[0359] Here, f sddm = -N c / 2,..., -N c / 2 + N Δfd-1, and N Δfd represents the number of Doppler frequency indices included in the interval of Δfd, N Δfd = round(Δfd / (1 / (T r N c ))). Additionally, round(x) is an operator that rounds the real number x and outputs an integer value.

[0360] Additionally, for example, the operation of CFAR processing can be based on the operation disclosed in Non-Patent Document 2, and the details of the operation example are omitted here.

[0361] Thus, the Doppler frequency range that is the object of CFAR processing in the CFAR unit 210 can be reduced from the entire range of the Doppler frequency index range f s (for example, the range of -N c / 2 to N c / 2 - 1) to the range of Δfd, so the computational amount of CFAR processing can be reduced to 1 / (Nt + δ) = 1 / (N DM + δ).

[0362] Then, the CFAR unit 210 sets a threshold value in an adaptive manner, and outputs the distance index f where the received power is greater than the threshold value, b_cfar the Doppler frequency index f sddm_cfar , and the received power information (PowerFT(f b_cfar , f sddm_cfar + (ndm - 1)×N Δfd )) to the Doppler multiplexing / demultiplexing unit 211. Here, ndm = an integer from 1 to N DM + δ.

[0363] <Example of operation of CFAR unit 210 2>

[0364] In Example of operation 2, an example of the operation of the CFAR unit 210 when the value of δ shown in Equation (3) is set to a real number that is not a positive integer in the Doppler frequency shift unit 104 is described.

[0365] The CFAR unit 210 can, for example, calculate the power addition value of Equation (9) based on the outputs of the Doppler analysis units 209 of the first to Na-th signal processing units 206, and detect the power peak that matches the Doppler frequency shift interval separately set for the radar transmission signal for each distance index through adaptive threshold processing (CFAR processing).

[0366] Then, the CFAR unit 210 sets a threshold value in an adaptive manner, and the distance index f where the received power is greater than the threshold value, b_cfar , the Doppler frequency index f of the power peak that matches the Doppler frequency shift interval set for the radar transmission signals_cfar (ndm), and the Doppler frequency index f s_cfar (ndm) receiving power information PowerFT(f b_cfar , f s_cfar (ndm)) is output to the Doppler multiplexing and demultiplexing unit 211. Here, ndm = 1 to N DM +δ integer.

[0367] The operation example of the CFAR unit 210 has been described above.

[0368] In the operation example of the Doppler multiplexing and demultiplexing unit 211 described later, the case where the output of the operation example 1 in the CFAR unit 210 is used is described as an example, but the present invention is not limited to this, and the output of the operation example 2 in the CFAR unit 210 may be used. When the output of the operation example 2 in the CFAR unit 210 is used, the Doppler frequency index f is output. s_cfar (ndm) is used instead of the Doppler frequency index f in the operation example 1 in the CFAR unit 210. sddm_cfar +(ndm-1)×N Δfd This is a difference, but other than that, it is the same operation and can achieve the same effect.

[0369] [Operation Example of Doppler Multiplexing and Demultiplexing Unit 211]

[0370] For example, when the value of δ shown in equation (3) is set to a positive integer in the Doppler frequency shift unit 104, the Doppler multiplexing and demultiplexing unit 211 performs the multiplication based on the distance index f input from the CFAR unit 210. b_cfar , Doppler frequency index f sddm_cfar , and received power information (PowerFT(f b_cfar , f sddm_cfar +(ndm-1)×N Δfd )), perform the following actions. It should be noted that ndm = 1 to N DM +δ integer.

[0371] In the following description, an operation example of the Doppler multiplexing and demultiplexing unit 211 is described when the multiple receiving antennas of the receiving antenna unit 202 are omnidirectional antennas (or antennas having a directional characteristic that is substantially uniform within the field of view angle covered by the transmitting antennas in the beam direction B1 and the beam direction B2). An operation example of the Doppler multiplexing and demultiplexing unit 211 is described when the multiple receiving antennas of the receiving antenna unit 202 include receiving antennas in different beam directions.

[0372] Fig.182 is a flowchart showing an example of the demultiplexing operation of the Doppler multiplexed signal in the Doppler multiplexer demultiplexer 211. In the following, it is assumed that the Doppler velocity of the target object is within the range of -1 / (2Tr)≦fd<1 / (2Tr).

[0373] <Step A-1>

[0374] The Doppler multiplexing and demultiplexing unit 211 performs multiplexing of Nt (=N DM The Doppler multiplexed signal is demultiplexed by performing Doppler multiplexing processing.

[0375] <Step A-2>

[0376] In this case, for example, it is assumed that the distance index f is input from the CFAR unit 210 b_cfar N DM +δ Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) contains N DM Doppler multiplexed signals with unequal spacing.

[0377] The Doppler multiplexing and demultiplexing unit 211 compares, for example, the Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) received power (PowerFT(f b_cfar , f sddm_cfar +(ndm-1)×N Δfd ))(For example, ndm = 1 to N DM +δ), determine the N with the highest received power DM Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) matches the Doppler frequency shift interval assigned when transmitting (for example, called "N DM Doppler frequency shift interval matching determination”).

[0378] In addition, the Doppler multiplexing and demultiplexing unit 211 determines, for example, that the N DM The received level of the Doppler frequency index is different from the N first received power. DM Is the difference (or reception level ratio) between the reception levels of δ other Doppler frequency indices of the Doppler frequency index of the first Doppler frequency index a large difference (for example, the difference is greater than a threshold, or the reception level ratio is greater than a threshold) (for example, referred to as “N DM Doppler multiplexed signal reception level difference determination").

[0379] The Doppler multiplexing and demultiplexing unit 211 determines, for example, the Doppler frequency and the transmission antenna corresponding to the Doppler multiplexed signal within the range of -1 / (2Tr)≦fd<1 / (2Tr) based on these determinations.

[0380] Note that, for example, Patent Document 7 discloses an operation example of the Doppler multiplexing and demultiplexing unit 211 that demultiplexes Doppler multiplexed signals with unequal intervals, and therefore a detailed description of the operation is omitted here.

[0381] For example, the Doppler multiplexing and demultiplexing unit 211 determines whether N DM Doppler frequency shift interval matching judgment and N DM The two conditions (e.g., the conditions of step A-2) are determined by the difference in the received level of the N Doppler multiplexed signals. DM The N received powers ranked first in the Doppler frequency shift interval matching judgment DM Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) matches the Doppler frequency shift interval assigned when transmitting, and in N DM When it is determined that the corresponding reception level difference is equal to or larger than the threshold value in the Doppler multiplexed signal reception level difference determination, the condition of step A-2 is satisfied.

[0382] The Doppler multiplexing and demultiplexing unit 211 may perform the process of step A-3 when the condition of step A-2 is satisfied, and may perform the process of step B-1 assuming that the target object direction is the beam direction B1 when the condition of step A-2 is not satisfied.

[0383] <Step A-3>

[0384] The Doppler multiplexing and demultiplexing unit 211 performs the multiplexing and demultiplexing based on the Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) with the lowest receiving level, and the N Doppler frequency indices with the highest receiving power. DM The Doppler frequency index relationship of the Nt Doppler multiplexed signals is used to calculate the Doppler frequency shift amounts DOP1, DOP2, ..., DOP Nt , corresponds to the Doppler frequency index, and serves as the demultiplexing index information DDM_RXindex(f b_cfar )=(f demul_Tx#1 , ..., f demul_Tx#NDM ), and the distance index f b_cfar The two signals are outputted together to the direction estimation unit 212 .

[0385] Here, f demul_Tx#nIndicates the Doppler frequency index of the reflected wave signal for the radar transmission signal transmitted from the nth transmission antenna (Tx#n).

[0386] In addition, the Doppler multiplexing and demultiplexing unit 211 outputs the output of the Doppler analysis unit 209 corresponding to these distances and the Doppler demultiplexing index to the direction estimation unit 212, for example.

[0387] In addition, the Doppler frequency shift amount given to each transmission antenna of the transmission antenna unit 105 in the Doppler frequency shift unit 104 of the radar transmission unit 100 is known. Therefore, the demultiplexing index information DDM_RXindex (f b_cfar ) and the difference between the Doppler frequency shift amount given to each transmitting antenna in the radar transmitting unit 100 is the Doppler frequency of the target object. Therefore, the Doppler demultiplexing unit 211 may replace the demultiplexing index information DDM_RXindex(f b_cfar ), the Doppler frequency of the target object estimated within the range of -1 / (2Tr)≦fd<1 / (2Tr) is output to the direction estimation unit 212. In this case, the direction estimation unit 212 generates demultiplexing index information DDM_RXindex (f b_cfar ), thereby being able to perform the same action.

[0388] <Step B-1>

[0389] The Doppler multiplexing and demultiplexing unit 211 assumes that the target direction is the beam direction B1, and B1 Doppler multiplexed signals are demultiplexed.

[0390] <Step B-2>

[0391] In this case, for example, it is assumed that the distance index f is input from the CFAR unit 210 b_cfar N DM +δ Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) contains N transmitting antennas from beam direction B1 B1 Doppler multiplexed signal.

[0392] The Doppler multiplexing and demultiplexing unit 211 compares, for example, the Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) received power (PowerFT(f b_cfar , f sddm_cfar+(ndm-1)×N Δfd ))(For example, ndm = 1 to N DM +δ), and determine the N with the highest received power B1 Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) matches the Doppler shift interval assigned to the transmitting antenna in beam direction B1 during transmission (for example, referred to as "beam direction B1 Doppler shift interval matching judgment").

[0393] In addition, for example, the Doppler multiplexing and demultiplexing unit 211 determines that the N B1 The received level of the Doppler frequency index is different from the N first received power. B1 Doppler frequency index (N DM +δ-N B1 ) is a large difference (for example, the difference is greater than a threshold, or the reception level ratio is greater than a threshold) (for example, referred to as "beam direction B1 Doppler multiplexing signal reception level difference judgment").

[0394] The Doppler multiplexing and demultiplexing unit 211 determines, for example, the Doppler frequency and the transmission antenna corresponding to the Doppler multiplexed signal within the range of -1 / (2Tr)≦fd<1 / (2Tr) based on these determinations.

[0395] Note that, for example, Patent Document 7 discloses an operation example of the Doppler multiplexing and demultiplexing unit 211 that demultiplexes Doppler multiplexed signals with unequal intervals, and therefore a detailed description of the operation is omitted here.

[0396] For example, the Doppler multiplexing demultiplexing unit 211 determines whether the two conditions of beam direction B1 Doppler frequency shift interval matching determination and beam direction B1 Doppler multiplexing signal reception level difference determination (for example, the condition of step B-2) are satisfied. For example, when the first N of the received power is determined to be matched in the beam direction B1 Doppler frequency shift interval matching determination, B1 Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) matches the Doppler frequency shift interval assigned to the transmitting antenna in the beam direction B1 during transmission, and when the corresponding receiving level difference is determined to be above the threshold in the Doppler multiplexing signal receiving level difference judgment in the beam direction B1, the condition of step B-2 is satisfied.

[0397] The Doppler multiplexing and demultiplexing unit 211 may perform the process of step B-3 when the condition of step B-2 is satisfied, and may perform the process of step C-1 assuming that the target object direction is the beam direction B2 when the condition of step B-2 is not satisfied.

[0398] In addition, in N B1 When the number=1, the beam direction B1 Doppler shift interval matching determination process may not be performed.

[0399] <Step B-3>

[0400] The Doppler multiplexing and demultiplexing unit 211 performs the multiplexing and demultiplexing based on the Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) with a small receiving level N DM +δ-N B1 Doppler frequency indexes and received power are ranked first N B1 The Doppler frequency index relationship of the Nt Doppler multiplexed signals is used to calculate the Doppler frequency shift amounts DOP1, DOP2, ..., DOP Nt , corresponds to the Doppler frequency index, and serves as the demultiplexing index information DDM_RXindex_ B1 (f b_cfar )=(f demul_Tx#1 , ..., f demul_Tx#NDM ), and the distance index f b_cfar The two signals are outputted together to the direction estimation unit 212 .

[0401] Here, f demul_Tx#n Indicates the Doppler frequency index of the reflected wave signal for the radar transmission signal transmitted from the nth transmission antenna (Tx#n).

[0402] In addition, the Doppler multiplexing and demultiplexing unit 211 outputs the output of the Doppler analysis unit 209 corresponding to these distances and the Doppler demultiplexing index to the direction estimation unit 212, for example.

[0403] In addition, the Doppler shift amount given to each transmission antenna of the transmission antenna unit 105 in the Doppler shift unit 104 of the radar transmission unit 100 is known. Therefore, the demultiplexing index information DDM_RXindex_ B1 (f b_cfar ) and the difference between the Doppler frequency shift amount given to each transmitting antenna in the radar transmitting unit 100 is the Doppler frequency of the target object. Therefore, the Doppler demultiplexing unit 211 may replace the demultiplexing index information DDM_RXindex_ B1 (f b_cfar), the Doppler frequency of the target object estimated within the range of -1 / (2Tr)≦fd<1 / (2Tr) is output to the direction estimation unit 212. In this case, the direction estimation unit 212 generates demultiplexing index information DDM_RXindex_ B1 (f b_cfar ), thereby being able to perform the same action.

[0404] Alternatively, the Doppler multiplexing and demultiplexing unit 211 may also multiplex the N beams in the beam direction B1 from the Nt transmitting antennas. B1 The Doppler frequency shift of the Doppler multiplexed signal of each transmitting antenna is matched with the Doppler frequency index, and the beam direction B1 demultiplexing index information of the Doppler multiplexed signal is used as DDM_Rxindex_ B1 (f b_cfar ), and the distance index f b_cfar The two signals are outputted together to the direction estimation unit 212 .

[0405] <Step C-1>

[0406] The Doppler multiplexing and demultiplexing unit 211 assumes that the target direction is the beam direction B2, and B2 Doppler multiplexed signals are demultiplexed.

[0407] <Step C-2>

[0408] In this case, for example, it is assumed that the distance index f is input from the CFAR unit 210 b_cfar N DM +δ Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) contains N transmitting antennas from beam direction B2 B2 Doppler multiplexed signal.

[0409] The Doppler multiplexing and demultiplexing unit 211 compares, for example, the Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) received power (PowerFT(f b_cfar , f sddm_cfar +(ndm-1)×N Δfd ))(For example, ndm = 1 to N DM +δ), and determine the N with the highest received power B2 Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd) matches the Doppler shift interval assigned to the transmitting antenna in beam direction B2 during transmission (for example, referred to as "beam direction B2 Doppler shift interval matching judgment").

[0410] In addition, for example, the Doppler multiplexing and demultiplexing unit 211 determines that the N B2 The received level of the Doppler frequency index is different from the N first received power. B2 Doppler frequency index (N DM +δ-N B2 ) is a large difference (for example, the difference is greater than a threshold, or the reception level ratio is greater than a threshold) (for example, referred to as "beam direction B2 Doppler multiplexing signal reception level difference judgment").

[0411] The Doppler multiplexing / demultiplexing unit 211 determines the Doppler frequency and the transmission antenna within the range of -1 / (2Tr)≦fd<1 / (2Tr), for example, based on these determinations.

[0412] Note that, for example, Patent Document 7 discloses an operation example of the Doppler multiplexing and demultiplexing unit 211 that demultiplexes Doppler multiplexed signals with unequal intervals, and therefore a detailed description of the operation is omitted here.

[0413] For example, the Doppler multiplexing demultiplexing unit 211 determines whether the two conditions of beam direction B2 Doppler frequency shift interval matching determination and beam direction B2 Doppler multiplexing signal reception level difference determination (for example, the condition of step C-2) are satisfied. For example, when the N first ranked signal with the highest reception power is determined in the beam direction B2 Doppler frequency shift interval matching determination, B2 Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) matches the Doppler frequency shift interval assigned to the transmitting antenna in the beam direction B2 during transmission, and when the corresponding receiving level difference is determined to be above the threshold in the Doppler multiplexing signal receiving level difference judgment in the beam direction B2, the condition of step C-2 is satisfied.

[0414] If the condition of step C-2 is met, the Doppler multiplexing and demultiplexing unit 211 can perform the processing of step C-3. In addition, if the condition of step C-2 is not met, the Doppler multiplexing and demultiplexing unit 211 can determine that the received signal is a noise component or an interference component and does not output it to the direction estimation unit 212 (step D).

[0415] In addition, in N B2 When the number=1, the beam direction B2 Doppler shift interval matching determination process may not be performed.

[0416] <Step C-3>

[0417] The Doppler multiplexing and demultiplexing unit 211 performs the multiplexing and demultiplexing based on the Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) with a small receiving level N DM +δ-N B2 Doppler frequency indexes and received power are ranked first N B2 The Doppler frequency index relationship of the Nt Doppler multiplexed signals is used to calculate the Doppler frequency shift amounts DOP1, DOP2, ..., DOP Nt , corresponds to the Doppler frequency index, and serves as the demultiplexing index information DDM_RXindex_ B2 (f b_cfar )=(f demul_Tx#1 , ..., f demul_Tx#NDM ), and the distance index f b_cfar The two signals are outputted together to the direction estimation unit 212 .

[0418] Here, f demul_Tx#n Indicates the Doppler frequency index of the reflected wave signal for the radar transmission signal transmitted from the nth transmission antenna (Tx#n).

[0419] In addition, the Doppler multiplexing and demultiplexing unit 211 outputs the output of the Doppler analysis unit 209 corresponding to these distances and the Doppler demultiplexing index to the direction estimation unit 212, for example.

[0420] In addition, the Doppler shift amount given to each transmission antenna of the transmission antenna unit 105 in the Doppler shift unit 104 of the radar transmission unit 100 is known. Therefore, the demultiplexing index information DDM_RXindex_ B2 (f b_cfar ) and the difference between the Doppler frequency shift amount given to each transmitting antenna in the radar transmitting unit 100 is the Doppler frequency of the target object. Therefore, the Doppler demultiplexing unit 211 may replace the demultiplexing index information DDM_RXindex_ B2 (f b_cfar ), the Doppler frequency of the target object estimated within the range of -1 / (2Tr)≦fd<1 / (2Tr) is output to the direction estimation unit 212. In this case, the direction estimation unit 212 generates demultiplexing index information DDM_RXindex_ B2 (f b_cfar), thereby being able to perform the same action.

[0421] In addition, the Doppler multiplexing and demultiplexing unit 211 may also multiplex the N beams in the beam direction B2 from the Nt transmitting antennas. B2 The Doppler frequency shift of the Doppler multiplexed signal of each transmitting antenna is matched with the Doppler frequency index, and the beam direction B2 demultiplexing index information of the Doppler multiplexed signal is used as DDM_Rxindex_ B2 (f b_cfar ), and the distance index f b_cfar The two signals are outputted together to the direction estimation unit 212 .

[0422] In the above, an operation example of the Doppler multiplexing and demultiplexing unit 211 has been described.

[0423] In addition, the distance index f input from the CFAR unit 210 b_cfar , Doppler frequency index f sddm_cfar and received power information (PowerFT(f b_cfar , f sddm_cfar +(ndm-1)×N Δfd )) When there are multiple Doppler multiplexing and demultiplexing units 211 can perform the above-mentioned Doppler multiplexing and demultiplexing operations on the distance index, Doppler frequency index and reception power information multiple times.

[0424] In addition, in the above-mentioned operation example of the Doppler multiplexing and demultiplexing unit 211, the case where the number of multi-beams NB=2 is described, but the number of multi-beams NB is not limited to this, for example, NB may be greater than 3. For example, in the case where the number of multi-beams NB=3, the Doppler multiplexing and demultiplexing unit 211 may Fig.18 In step D (or between step C-2 and step D), the demultiplexing process of Doppler multiplexing is further continued for beam directions different from beam directions B1 and B2 (or overlapping beam ranges or different beams. For example, beam direction B3). Thus, even when the number of multi-beams is further increased, the demultiplexing action of Doppler multiplexing can be performed in the same manner.

[0425] [Operation Example of Direction Estimation Unit 212]

[0426] Next, Figure 7 The operation example of the direction estimation unit 212 shown in FIG. 2 is described below.

[0427] In the following description, an example of operation of the direction estimation unit 212 is described when the multiple receiving antennas of the receiving antenna unit 202 are identical omnidirectional antennas or antennas having substantially uniform directional characteristics within the field of view of the transmitting antennas in multiple different beam directions.

[0428] The direction estimation unit 212 generates a Doppler multiplexing and demultiplexing signal based on the information input from the Doppler multiplexing and demultiplexing unit 211 (for example, the distance index f b_cfar , demultiplexing index information of Doppler multiplexed signal (DDM_Rxindex(f b_cfar )=(f demul_Tx#1 , f demul_Tx#2 , ..., f demul_Tx#Nt ) or DDM_Rxindex_ Bq (f b_cfar )) and the output of the Doppler analysis unit 209 corresponding to these distances and Doppler demultiplexing indexes, and the direction estimation process of the target object is performed. Here, for example, q=1 or 2.

[0429] Hereinafter, operation example 1 and operation example 2 of the direction estimation unit 212 will be described.

[0430] <Operation Example 1 of Direction Estimation Unit 212>

[0431] For example, the direction estimation unit 212 calculates the distance index f b_cfar And the demultiplexing index information DDM_Rxindex(f b_cfar ), extract the output of the Doppler analysis unit 209, and generate the virtual receiving array correlation vector h(f) of the direction estimation unit 212 shown in the following equation (10): b_cfar , DDM_Rxindex(f b_cfar )) to perform direction estimation processing.

[0432] Here, the information input from the Doppler multiplexing and demultiplexing unit 211 includes the demultiplexing index information (DDM_Rxindex(f b_cfar )=(f demul_Tx#1 , f demul_Tx#2 , ..., f demul_Tx#Nt ), contains Doppler demultiplexing information for Nt transmitting antennas. Therefore, as shown in equation (10), the virtual receiving array correlation vector h(f b_cfar , DDM_Rxindex(f b_cfar )) contains Nt×Na elements, which is the product of the number of transmitting antennas Nt and the number of receiving antennas Na. The direction estimation unit 212 uses the virtual receiving array correlation vector h(f b_cfar , DDM_Rxindex(f b_cfar )), the direction of the reflected wave signal from the target is estimated based on the phase difference between each transmitting and receiving antenna.

[0433] [Formula 10]

[0434]

[0435] In formula (10), h cal[b] b is an array correction value for correcting the phase deviation and amplitude deviation between the transmission antennas and the reception antennas. b = an integer from 1 to (Nt×Na).

[0436] The direction estimation unit 212 uses, for example, a virtual receiving array correlation vector h(f b_cfar , DDM_Rxindex(f b_cfar )), change the direction within the specified angle range to estimate the evaluation function P H (θ u , f b_cfar , DDM_Rxindex(f b_cfar )) in the azimuth direction θ u , to calculate the spatial distribution.

[0437] The direction estimation unit 212 may extract a predetermined number of maximum peaks from the calculated maximum peaks of the spatial distribution in descending order, and output the azimuth directions of the maximum peaks as arrival direction estimation values ​​(eg, positioning output).

[0438] In addition, regarding the direction estimation evaluation function value P H (θ u , f b_cfar , DDM_Rxindex(f b_cfar )), there are various methods based on the arrival direction estimation algorithm. For example, the estimation method using an array antenna disclosed in non-patent document 3 can also be used.

[0439] For example, when the number of virtual receiving antennas is Nt×Na and they are arranged linearly at equal intervals dH, the beamforming method can be expressed as in the following equation (11). In addition to the beamforming method, methods such as Capon and MUSIC can also be applied.

[0440] [Formula 11]

[0441] P H (θ u , f b_cfar , DDM_Rxindex(f b_cfar ))

[0442] =a H (θ u )h(f b_cfar DDM_Rxindex(f b_cfar )) (11)

[0443] In formula (11), the superscript H is the Hermitian transposition operator. In addition, in formula (11), a(θ u) represents the azimuth direction θ at the center frequency fc of the radar signal u The direction vector of the virtual receiving array of the arrival wave is shown in equation (12), and is a column vector with Nt×Na elements. In equation (12), λ is the center frequency f c The wavelength of the radar signal (e.g., chirp signal) transmitted at the time, λ = C0 / f c .

[0444] [Formula 12]

[0445]

[0446] In addition, the azimuth direction θ u is a vector that changes at a predetermined azimuth interval β1 within the azimuth range for estimating the direction of arrival. For example, θ is set as follows u .

[0447] θ u =θ min +uβ1, integer u=0~NU

[0448] NU=floor[(θmax-θmin) / β1]+1

[0449] Here, floor(x) is a function that returns the largest integer value that does not exceed the real number x.

[0450] In addition, in the above example, the direction estimation unit 212 calculates the azimuth direction as an example of an estimated value of the direction of arrival, but the present invention is not limited thereto, and the direction of arrival in the elevation direction may be estimated by using virtual receiving antennas arranged in the elevation direction, or the direction of arrival in the azimuth direction and the elevation direction may be estimated by using virtual receiving antennas arranged in the azimuth direction and the elevation direction in a rectangular grid shape, etc. For example, the direction estimation unit 212 may calculate the azimuth direction and the elevation direction as estimated values ​​of the direction of arrival for the transmitting antennas in different beam directions, and output them as positioning.

[0451] Through the above operations, the direction estimation unit 212 of the radar device 10 can output the distance index f as a positioning output, for example. b_cfar , demultiplexing index information DDM_Rxindex(f b_cfar )=(f demul_Tx#1 , ..., f demul_Tx#NDM ) under the estimated value of the direction of arrival. In addition, as the positioning output, the direction estimation unit 212 can also output the distance index f b cfar And the demultiplexing index information DDM_Rxindex(f b_cfar ).

[0452] In addition, the direction estimation unit 212 may also use the demultiplexing index information DDM_Rxindex(f b_cfar ), and outputs the Doppler frequency estimate of the target.

[0453] Alternatively, the distance index f can be converted to b_cfar Convert it into distance information and output it.

[0454] In addition, the information input from the Doppler multiplexing and demultiplexing unit 211 (for example, the distance index f b_cfar , and demultiplexing index information DDM_Rxindex(f b_cfar )=(f demul_Tx#1 , f demul_Tx#2 , ..., f demul_Tx#Nt )) When there are multiple ones, the direction estimation unit 212 can calculate the arrival direction estimation values ​​for them in the same way as the above processing and output the positioning results.

[0455] <Operation Example 2 of Direction Estimation Unit 212>

[0456] For example, the direction estimation unit 212 calculates the distance index f b_cfar And the demultiplexing index information DDM_Rxindex_Bq(f b_cfar ), extract the output of the Doppler analysis unit 209, and generate the virtual receiving array correlation vector h of the direction estimation unit 212 q (f b_cfar , DDM_Rxindex(f b_cfar )), and performs direction estimation processing based on the received signal corresponding to the transmitting antenna of the beam direction Bq. Here, q = 1, ..., NB. For example, when the number of multi-beams NB = 2, q = 1 or 2. The following describes the operation in the case of NB = 2, but is not limited to this. For example, the direction estimation unit 212 performs demultiplexing index information DDM_Rxindex_Bq (f b_cfar ) direction estimation processing of the beam direction Bq corresponding to the consistent q.

[0457] For example, the direction estimation unit 212 extracts the Bq beam antenna vector SP corresponding to the radar transmission signal from the transmission antenna in the beam direction Bq in order to perform the direction estimation process based on the received signal corresponding to the radar transmission signal from the transmission antenna in the beam direction Bq. Bq and the virtual receiving array correlation vector h(f b_cfar , DDM_Rxindex_Bq(f b_cfar)) to generate the Bq beam antenna virtual receiving array correlation vector h Bq (f b_cfar , DDM_Rxindex_Bq(f b_cfar )). Here, h Bq (f b_cfar , DDM_Rxindex_Bq(f b_cfar )) is a Bq ×Na-element column vector.

[0458] For example, the transmitting antennas in beam direction B1 are Tx#1 and Tx#3, the transmitting antennas in beam direction B2 are Tx#2 and Tx#4, and N B1 =2, N B2 =2, N t =4, when the number of receiving antennas Na=4, the B1 beam antenna extraction vector SP of the received signal corresponding to the transmitting antenna in the beam direction B1 is extracted B1 , and a B2 beam antenna extraction vector SP for extracting a received signal corresponding to the transmitting antenna of the beam direction B2 B2 It can be expressed as 16(=N) using the following formula (13) and the following formula (14): t Here, the superscript T represents the vector transpose.

[0459] [Formula 13]

[0460] SP B1 =[1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0] T (13)

[0461] [Formula 14]

[0462] SP B2 =[0,0,0,0,1,1,1,1,0,0,0,0,1,1,1,1] T (14)

[0463] The direction estimation unit 212 uses, for example, the B1 beam antenna to extract the vector SP B1 The element index of the element with 1 is the element index of the virtual receiving array related vector h(f b_cfar , DDM_Rxindex_B1(f b_cfar )) extract the element components of the element index and arrange them in ascending order according to the element index, and use the arranged column vector as the virtual receiving array correlation vector h based on the B1 beam antenna B1 (f b_cfar , DDM_Rxindex_B1(f b_cfarFor example, the B1 beam antenna extraction vector SP shown in equation (13) B1 The first to fourth and ninth to twelfth elements of the element index of are 1. In this case, the direction estimation unit 212 obtains the virtual receiving array correlation vector h(f b_cfar , DDM_Rxindex_B1(f b_cfar )) and extract the element components in the order of the 1st to 4th and 9th to 12th element indexes to generate the B1 beam antenna virtual receiving array correlation vector h B1 (f b_cfar , DDM_Rxindex_B1(f b_cfar )).

[0464] Similarly, the direction estimation unit 212 uses, for example, the B2 beam antenna to extract the vector SP B2 The element index of the element with 1 is the element index of the virtual receiving array related vector h(f b_cfar , DDM_Rxindex_B2(f b_cfar )) extract the element components of the element index and arrange them in ascending order according to the element index, and use the arranged column vector as the virtual receiving array correlation vector h based on the B2 beam antenna B2 (f b_cfar , DDM_Rxindex_B2(f b_cfar For example, the B2 beam antenna extraction vector SP shown in equation (14) B2 The 5th to 8th and 13th to 16th elements of the element index of are 1. In this case, the direction estimation unit 212 obtains the virtual receiving array correlation vector h(f b_cfar , DDM_Rxindex_B2(f b_cfar )), extract the element components in the order of the 5th to 8th and 13th to 16th element indexes to generate the B2 beam antenna virtual receiving array correlation vector h B2 (f b_cfar , DDM_Rxindex_B2(f b_cfar )).

[0465] The direction estimation unit 212 uses, for example, a Bq beam antenna virtual receiving array correlation vector h Bq (f b_cfar , DDM_Rxindex_Bq(f b_cfar )), change the direction within the specified angle range to estimate the evaluation function P H-Bq (θ u , f b_cfar , DDM_Rxindex_Bq(f b_cfar )) in the azimuth direction θ u, to calculate the spatial distribution based on each Bq beam. Here, q=1 or 2.

[0466] The direction estimation unit 212 can extract a specified number of maximum peaks from the maximum peaks of the spatial distribution of the received signal corresponding to the transmitting antenna based on the calculated beam direction Bq in order from large to small, and output the azimuth direction of the maximum peak as an arrival direction estimation value based on the Bq beam (for example, positioning output).

[0467] In addition, regarding the direction estimation evaluation function value P H-Bq (θ u , f b_cfar , DDM_Rxindex_Bq(f b_cfar )), there are various methods based on the arrival direction estimation algorithm. For example, the estimation method using an array antenna disclosed in non-patent document 3 can also be used.

[0468] In addition, in the above example, the direction estimation unit 212 calculates the azimuth direction as an example of an estimated value of the direction of arrival, but the present invention is not limited thereto, and the direction of arrival in the elevation direction may be estimated by using virtual receiving antennas arranged in the elevation direction, or the direction of arrival in the azimuth direction and the elevation direction may be estimated by using virtual receiving antennas arranged in the azimuth direction and the elevation direction in a rectangular grid shape, etc. For example, the direction estimation unit 212 may calculate the azimuth direction and the elevation direction as estimated values ​​of the direction of arrival and output them as positioning.

[0469] Through the above operation, the direction estimation unit 212 of the radar device 10 can output the positioning result according to the distance index f b_cfar , demultiplexing index information DDM_Rxindex(f b_cfar )_Bq=(f demul_Tx#1 , ..., f demul_Tx#NDM ) receives the received signal from the transmitting antenna in the beam direction Bq, and outputs the estimated arrival direction based on the Bq beam. In addition, as the positioning output, the direction estimation unit 212 can also output the distance index f b_cfar And the demultiplexing index information DDM_Rxindex_Bq(f b_cfar ).

[0470] In addition, the direction estimation unit 212 may also use the demultiplexing index information DDM_Rxindex_Bq (f b_cfar ), and outputs the Doppler frequency estimate of the target.

[0471] Alternatively, the distance index f can be converted to b_cfar Convert it into distance information and output it.

[0472] In addition, the information input from the Doppler multiplexing and demultiplexing unit 211 (for example, the distance index f b_cfar , and the demultiplexing index information DDM_Rxindex_Bq(f b_cfar )=(f demul_Tx#1 , f demul_Tx#2 , ..., f demul_Tx#Nt )) When there are multiple ones, the direction estimation unit 212 can calculate the arrival direction estimation values ​​for them in the same way as the above processing and output the positioning results.

[0473] In the above, operation example 1 and operation example 2 of the direction estimation unit 212 have been described.

[0474] Next, an example of arrangement of the MIMO antenna and an example of operation of the direction estimation unit 212 when the example of arrangement of the MIMO antenna is used will be described. In the following, the transmission antenna and the reception antenna in the MIMO radar are collectively referred to as MIMO antennas.

[0475] In the following description, each transmitting antenna included in the transmitting antenna unit 105 may be, for example, Fig.19 As shown in FIG. 1 , a plurality of planar patch antennas are arranged in a subarray structure in the longitudinal and transverse directions. Fig.19 In the example, the transmitting antenna is composed of 8 planar patch antennas in the vertical direction and 4 planar patch antennas in the horizontal direction. For example, by changing the power supply phase for each patch antenna included in a transmitting antenna, a beam pattern (element pattern of the transmitting antenna) in which a directional beam is directed in a desired direction can be formed. In addition, for example, the more planar patch antennas in the horizontal (or vertical) direction that constitute a transmitting antenna, the sharper the directional beam in the horizontal (or vertical) direction can be formed. For example, a transmitting antenna can be composed of a number of planar patches that meet the desired beam width.

[0476] In addition, the structure of a transmitting antenna is not limited to Fig.19 In the example shown, the number of patch antennas constituting one transmitting antenna (for example, at least one of the total number, the number in the horizontal direction, and the number in the vertical direction) is not limited to Fig.19 In addition, one transmitting antenna is not limited to a planar patch antenna, and may be a structure in which patch antennas are arranged in either the longitudinal direction or the lateral direction.

[0477] [Configuration Example A]

[0478] Arrangement example A is an arrangement example of MIMO antennas when one transmission antenna corresponds to each transmission beam. In arrangement example A, each transmission beam may be formed by one transmission antenna.

[0479] As an example, the antenna arrangement of a MIMO radar with the number of transmitting antennas Nt=2 (for example, Tx#1, Tx#2) and the number of receiving antennas Na=3 (for example, Rx#1, Rx#2, Rx#3) is described below.

[0480] For example, Fig. 20 As shown, the transmitting antennas Tx#1 and Tx#2 have different directivity patterns with different transmission beam directions (or directional beam directions). Fig. 20 In the example A, Tx#1 is the directivity pattern of beam direction B1 (beam B1), and Tx#2 is the directivity pattern of beam direction B2 (beam B2). Fig. 20 As shown, the number of transmitting antennas with the directivity pattern having the beam direction B1 and the number of transmitting antennas with the directivity pattern having the beam direction B2 are each 1, and N B1 =1,N B2 =1.

[0481] In addition, below, the directivity of the receiving antennas (e.g., Rx#1, Rx#2, Rx#3) can be non-directional, or a directional characteristic that is approximately uniform within the field of view of the transmitting antennas (e.g., Tx#1 and Tx#2) in multiple beam directions.

[0482] For example, when the number of transmission antennas used for multiplex transmission is Nt=2, the radar device 10 uses the Doppler multiplexing number N in the Doppler frequency shift unit 104. DM = 2 Doppler multiplexing signals to transmit radar transmission signals. In this case, for example, in the setting of the above-mentioned Doppler frequency shift amount, N can be applied. B1 =1, N B2 =1 Doppler multiplexing signal allocation.

[0483] In addition, for example, virtual reception antenna (or MIMO virtual antenna) configurations VA#1 to VA#6 are composed of transmission antennas Tx#1 and Tx#2 and reception antennas Rx#1 to Rx#3.

[0484] Here, the configuration of the virtual receiving antenna (virtual receiving array) can be based on the position of the transmitting antenna constituting the transmitting antenna unit 105 (for example, the position of the power supply point) and the position of the receiving antenna constituting the receiving antenna unit 202 (for example, the position of the power supply point), as expressed by the following equation (15).

[0485] [Formula 15]

[0486]

[0487] Here, the position coordinates of the transmission antenna (for example, Tx#n) constituting the transmission antenna unit 105 are represented as (X T_#n , Y T_#n)(for example, n=1, ..., Nt), the position coordinates of the receiving antenna (for example, Rx#z) constituting the receiving antenna unit 202 are expressed as (X R_#z , Y R_#z )(for example, z=1, ..., Na), the position coordinates of the virtual antenna VA#b constituting the virtual receiving array antenna are expressed as (X V_#b , Y V_#b )(for example, b=1,…,Nt×Na).

[0488] In addition, in the formula (15), for example, VA#1 is expressed as the position reference (0, 0) of the virtual receiving array.

[0489] Next, the configuration examples A-1, A-2, and A-3 of the MIMO antenna are described. T_#n Indicates the horizontal position coordinate, Y T_#n The description is given by indicating the position coordinates in the vertical direction, but the present invention is not limited to this.

[0490] <Configuration Example A-1>

[0491] Fig.21 An example of antenna arrangement of arrangement example A-1 is shown. Fig.21 (a) shows an example of the configuration of MIMO antennas (Tx#1, Tx#2, Rx#1 to Rx#3). Fig.21 (b) indicates that Fig.21 An example of arrangement of virtual receiving antennas (VA#1 to VA#6) configured by the MIMO antenna arrangement of (a).

[0492] like Fig.21 As shown in (a), in the configuration example A-1, the receiving antennas Rx#1 to Rx#3 are arranged in the horizontal direction ( Fig.21 In the configuration example A-1, the transmitting antennas Tx#1 and Tx#2 are arranged at an interval of Dr in the horizontal direction (Dt=Dr), and in the vertical direction ( Fig.21 Configured at different positions (for example, at intervals of Dv) in the longitudinal direction.

[0493] For example, in Fig.21 The configuration of the transmitting antennas Tx#1 and Tx#2 shown in (a) is (X T_#1 , Y T_#1 )=(0,0)、(X T_#2 , Y T_#2 )=(D r , D V ), the configuration of receiving antennas Rx#1~Rx#3 is (X R_#1 , Y R_#1 )=(ax,ay),(XR_#2 , Y R_#2 )=(ax+D r ,ay),(X R_#3 , Y R_#3 )=(ax+2D r , ay), the position coordinates of the virtual antennas VA#1 to VA#6 constituting the virtual receiving antennas are calculated by equation (15). Here, ax and ay are arbitrary constants.

[0494] For example, the position coordinates of virtual antennas VA#1 to VA#6 are as follows: Fig.21 As shown in (b), it does not depend on ax and ay, but is respectively (X V_#1 , Y V_#1 )=(0,0)、(X V_#2 , Y V_#2 )=(D r ,0)、(X V_#3 , Y V_#3 )=(2D r ,0)、(X V_#4 , Y V_#4 )=(D r , D V )、(X V_#5 , Y V_#5 )=(2D r , D V )、(X V_#6 , Y V_#6 )=(3D r , D V ).

[0495] For example, in the above-mentioned operation example 1 of the direction estimation unit 212, the information input from the Doppler multiplexing and demultiplexing unit 211 includes the demultiplexing index information DDM_Rxindex (f b_cfar )=(f demul_Tx#1 , f demul_Tx#2 , …, f demul_Tx#Nt ), the direction estimation unit 212 generates the virtual receiving array correlation vector h(f) shown in equation (10) b_cfar , DDM_Rxindex(f b_cfar )) and perform direction estimation processing.

[0496] Here, the received signal based on the b-th virtual antenna VA#b is represented by the virtual receiving array correlation vector h(f b_cfar , DDM_Rxindex(f b_cfar ))'s b-th element represents.

[0497] In addition, the demultiplexing index information DDM_Rxindex(f b_cfar ) contains Doppler demultiplexing information for Nt transmitting antennas. This is the direction of the target object, for example Fig. 20 The case of the target object direction (2) shown corresponds to the case where the beam directions of the transmitting antenna Tx#1 and the transmitting antenna Tx#2 overlap. In this case, the radar transmission signals from both the transmitting antennas Tx#1 and Tx#2 are reflected by the target object and received by the receiving antennas Rx#1 to Rx#3. Therefore, in this case, the direction estimation unit 212 can use the received signals of the virtual antennas VA#1 to VA#6 corresponding to both Tx#1 and Tx#2 to perform direction estimation.

[0498] exist Fig.21 In the MIMO antenna configuration of (a), Tx#1 has a directional characteristic of beam direction B1, and Tx#2 has a directional characteristic of beam direction B2, which correspond to different beam directions. Fig. 20 As shown, the beam directions of Tx#1 and Tx#2 overlap in an angular region within the range of the beam width. Fig.21 As shown in (a), in the configuration of Tx#1 and Tx#2, an offset (offset value Dv) is made in the vertical direction, so when the target object exists in the overlapping area of ​​the beam directions of Tx#1 and Tx#2 (for example, Fig. 20 When the target object direction (2) is shown, the direction estimation unit 212 can measure the angle in the vertical direction in addition to the horizontal direction.

[0499] In addition, Fig.21 In the configuration of Tx#1 and Tx#2 shown in (a), the horizontal offset Dt is Dt=Dr. Thus, Tx#1 and Tx#2 are configured with an offset in the horizontal direction at an element spacing equal to the element spacing Dr of the receiving antennas Rx#1 to Rx#3. Fig.21 As shown in (b), the virtual receiving antenna configuration includes a configuration in which the horizontal positions of multiple virtual antennas (e.g., VA#2 and VA#4, or VA#3 and VA#5) are consistent but the vertical positions differ by Dv. With such a configuration of virtual receiving antennas, the direction estimation unit 212 can, for example, simply measure the vertical angle based on the reception phase difference between two virtual antennas (e.g., VA#2 and VA#4, or VA#3 and VA#5) that are consistent in horizontal positions.

[0500] In the operation example 1 of the direction estimation unit 212, Fig.21In the above example, Dt and Dr can be set to be greater than one wavelength. In this case, the result of the direction estimation processing in the direction estimation unit 212 may cause ambiguity in the horizontal direction estimation due to the presence of grating lobes. The direction estimation unit 212, for example, uses the demultiplexing index information DDM_Rxindex(f b_cfar ) to determine that there is an object target in the direction of the overlapping area of ​​beam direction B1 and beam direction B2. Therefore, even if grating lobes appear, the true value direction can be detected.

[0501] In the above-mentioned operation example 2 of the direction estimation unit 212, the information input from the Doppler multiplexing and demultiplexing unit 211 includes the demultiplexing index information DDM_Rxindex_Bq (f b_cfar ), the direction estimation unit 212 calculates the virtual receiving array correlation vector h(f b_cfar , DDM_Rxindex_Bq(f b_cfar )) and Bq beam antenna extraction vector SP Bq , generating the Bq beam antenna virtual receiving array correlation vector h Bq (f b_cfar , DDM_Rxindex_Bq(f b_cfar )) and perform direction estimation processing.

[0502] Here, the received signal based on the b-th virtual antenna VA#b is represented by the virtual receiving array correlation vector h(f b_cfar , DDM_Rxindex(f b_cfar ))'s b-th element represents.

[0503] In addition, the demultiplexing index information DDM_Rxindex_Bq (f b_cfar ) includes for N Bq The Doppler demultiplexing information of the transmitting antenna with a beam direction Bq is Fig. 20 The case of the target object direction (1) (e.g., the case of beam direction B1) or the case of the target object direction (3) (e.g., the case of beam direction B2) shown corresponds to the area of ​​the beam direction of the transmitting antenna Tx#q. In this case, the radar transmission signal from the transmitting antenna Tx#q is reflected by the target object and received by the receiving antennas Rx#1 to Rx#3.

[0504] Therefore, in this case, for example, when q=1 (the direction of the object is Fig. 20In the case of the target object direction (1) shown in FIG. 1 ), the direction estimation unit 212 can use the received signals of the virtual antennas VA#1 to VA#3 corresponding to Tx#1 to perform direction estimation. In addition, for example, in the case of q=2 (the target object direction is Fig. 20 In the case of the target object direction (3) shown in FIG. 1 ), the direction estimation unit 212 can perform direction estimation using the received signals of the virtual antennas VA#4 to VA#6 corresponding to Tx#2.

[0505] In the operation example 2 of the direction estimation unit 212, Fig.21 In the example, Dr can be set to be greater than 1 wavelength. In this case, the result of the direction estimation processing in the direction estimation unit 212 may cause ambiguity in the horizontal direction estimation due to the presence of grating lobes. The direction estimation unit 212, for example, uses the demultiplexing index information DDM_Rxindex_Bq (f b_cfar ) to determine that there is an object target in the direction of beam direction B1 or beam direction B2. Therefore, even if a grating lobe appears, the true value direction can be detected.

[0506] <Configuration Example A-2>

[0507] Fig. 22 An example of antenna configuration of configuration example A-2 is shown. Fig. 22 (a) shows an example of the configuration of MIMO antennas (Tx#1, Tx#2, Rx#1 to Rx#3). Fig. 22 (b) indicates that Fig. 22 An example of arrangement of virtual receiving antennas (VA#1 to VA#6) configured by the MIMO antenna arrangement of (a).

[0508] like Fig. 22 As shown, in configuration example A-2, receiving antennas Rx#1 to Rx#3 are arranged in the horizontal direction ( Fig. 22 In the configuration example A-2, the transmitting antennas Tx#1 and Tx#2 are arranged at an interval of Dt in the horizontal direction and at an interval of Dt in the vertical direction. Fig. 22 The distances Dt and Dr may be arranged at the same position (for example, without offset) in the longitudinal direction of the radar. In addition, the difference between the distance Dt and the distance Dr may be a predetermined value (for example, half a wavelength) based on the wavelength λ of the radar transmission signal.

[0509] For example, in Fig. 22 The configuration of the transmitting antennas Tx#1 and Tx#2 shown in (a) is (X T_#1 , Y T_#1 )=(0,0)、(X T_#2 , Y T_#2 )=(D t , 0), the configuration of receiving antennas Rx#1~Rx#3 is (XR_#1 , Y R_#1 )=(ax,ay),(X R_#2 , Y R_#2 )=(ax+D r ,ay),(X R_#3 , Y R_#3 )=(ax+2D r , ay), the position coordinates of the virtual antennas VA#1 to VA#6 constituting the virtual receiving antennas are calculated by equation (15). Here, ax and ay are arbitrary constants.

[0510] For example, Fig. 22 As shown in (b), the position coordinates of the virtual antennas VA#1 to VA#6 do not depend on ax and ay, but are respectively (X V_#1 , Y V_#1 )=(0,0)、(X V_#2 , Y V_#2 )=(D r ,0)、(X V_#3 , Y V_#3 )=(2D r ,0)、(X V_#4 , Y V_#4 )=(D t ,0)、(X V_#5 , Y V_#5 )=(D t +D r ,0)、(X V_#6 , Y V_#6 )=(D t +2D r , 0).

[0511] For example, the operation example 1 of the direction estimation unit 212 is that the direction of the object is Fig. 20 The case of the target object direction (2) shown corresponds to the case where the beam directions of the transmitting antennas Tx#1 and Tx#2 overlap. In this case, the radar transmission signals from both transmitting antennas Tx#1 and Tx#2 are reflected by the target object and received by receiving antennas Rx#1 to Rx#3. Therefore, in this case, the direction estimation unit 212 can use the received signals of the virtual antennas VA#1 to VA#6 corresponding to both Tx#1 and Tx#2 to perform direction estimation.

[0512] exist Fig. 22 In the MIMO antenna configuration of (a), Tx#1 has a directional characteristic of beam direction B1, and Tx#2 has a directional characteristic of beam direction B2, which correspond to different beam directions. Fig. 20 As shown, the beam directions of Tx#1 and Tx#2 overlap in an angular region within the range of the beam width. Fig. 22 As shown in (a), in the configuration of Tx#1 and Tx#2, an offset (offset value Dt) is performed in the horizontal direction. Therefore, Fig. 22 As shown in (b), in the virtual receiving antenna configuration, the aperture length in the horizontal direction is enlarged. Therefore, in the overlapping area where the target exists in the beam directions of Tx#1 and Tx#2 (for example, Fig. 20 In the case of the target object direction (2) shown in FIG. 1 , the angular resolution is improved in the direction estimation process of the direction estimation unit 212 .

[0513] In addition, Fig. 22 In (b), for example, the interval between virtual antennas VA#2 and VA#4 and the interval between virtual antennas VA#3 and VA#5 are Dt-Dr when Dt>Dr, and Dr-Dt when Dr>Dt. For example, when the absolute value |Dt-Dr| of the difference between the transmission antenna interval Dt and the reception antenna interval Dr is set to half a wavelength, in the radar device 10, grating lobes can be suppressed within a field of view of ±90°. For example, when Dt=1.5λ and Dr=1λ, Dt-Dr=0.5λ.

[0514] In addition, the case where the difference between Dt and Dr |Dt-Dr| (specified value) is set to half the wavelength (0.5λ) is described, but the present invention is not limited to this. For example, |Dt-Dr| can also be set to a value in the range of about 0.45λ to 0.8λ (for example, a value in the range of 0.5 to 0.8 times the wavelength of the radar signal).

[0515] |Dt-Dr| can be set, for example, according to the field of view of the radar device 10 in the horizontal direction, and the grating lobe within the field of view can be suppressed. For example, in the case of a wide field of view in the range of about ±70 degrees to ±90 degrees in the horizontal direction, |Dt-Dr| can be set to about 0.5λ. Alternatively, in the case of a narrow field of view in the range of about ±20 degrees to ±40 degrees in the horizontal direction, |Dt-Dr| can be set to about 0.7λ as a wider interval, for example.

[0516] In addition, Dv in configuration example A-2 and other configuration examples can be set to values ​​of about 0.45λ to 0.8λ (for example, a value in the range of 0.5 times to 0.8 times the wavelength of the radar transmission signal). Dv can be set, for example, according to the vertical field of view of the radar device 10. For example, in the case of a wide field of view in the range of about ±70 degrees to ±90 degrees in the vertical direction, Dv can be set to about 0.5λ. Alternatively, in the case of a narrow field of view in the range of about ±20 degrees to ±40 degrees in the vertical direction, Dv can be set to about 0.7λ as a wider interval.

[0517] Here, λ represents the wavelength of the carrier frequency of the radar transmission signal. For example, when a chirp signal is used as the radar transmission signal, λ is the wavelength of the center frequency of the frequency sweep band of the chirp signal.

[0518] In addition, the operation example 2 of the direction estimation unit 212 is that the direction of the object is, for example, Fig. 20 The case of the target object direction (1) or target object direction (3) shown corresponds to the area of ​​the beam direction of the transmitting antenna Tx#q. In this case, the radar transmission signal from the transmitting antenna Tx#q is reflected by the target object and received by the receiving antennas Rx#1 to Rx#3.

[0519] Therefore, in this case, for example, when q=1 (the direction of the object is Fig. 20 In the case of the target object direction (1) shown in FIG. 1 ), the direction estimation unit 212 can use the received signals of the virtual antennas VA#1 to VA#3 corresponding to Tx#1 to perform direction estimation. In addition, for example, in the case of q=2 (the target object direction is Fig. 20 In the case of the target object direction (3) shown in the figure), the direction estimation unit 212 can use the received signals of the virtual antennas VA#4 to VA#6 corresponding to Tx#2 to perform direction estimation. In the case of operation example 2 of the direction estimation unit 212 of configuration example A-2, the configuration is the same as that of configuration example A-1, and the same effect as that of configuration example A-1 is obtained.

[0520] <Configuration Example A-3>

[0521] Fig.23 An example of antenna configuration of configuration example A-3 is shown. Fig.23 (a) shows an example of the configuration of MIMO antennas (Tx#1, Tx#2, Rx#1 to Rx#3). Fig.23 (b) indicates that Fig.23 An example of arrangement of virtual receiving antennas (VA#1 to VA#6) configured by the MIMO antenna arrangement of (a).

[0522] like Fig.23 As shown, in configuration example A-3, receiving antennas Rx#1 to Rx#3 are arranged in the horizontal direction ( Fig.23 In the configuration example A-3, the transmitting antennas Tx#1 and Tx#2 are arranged at an interval of Dt in the horizontal direction and at an interval of Dt in the vertical direction. Fig.23 The distance Dt and the distance Dr may be arranged at different positions (for example, with an offset Dv) in the longitudinal direction of the radar. In addition, the difference between the distance Dt and the distance Dr may be a specified value (for example, half a wavelength) based on the wavelength λ of the radar transmission signal.

[0523] For example, in Fig.23The configuration of the transmitting antennas Tx#1 and Tx#2 shown in (a) is (X T_#1 , Y T_#1 )=(0,0)、(X T_#2 , Y T_#2 )=(D t , D v ), the configuration of receiving antennas Rx#1~Rx#3 is (X R_#1 , Y R_#1 )=(ax,ay),(X R_#2 , Y R_#2 )=(ax+D r ,ay),(X R_#3 , Y R_#3 )=(ax+2D r , ay), the position coordinates of the virtual antennas VA#1 to VA#6 constituting the virtual receiving antennas are calculated by equation (15). Here, ax and ay are arbitrary constants.

[0524] For example, the position coordinates of virtual antennas VA#1 to VA#6 are as follows: Fig.23 As shown in (b), it does not depend on ax and ay, but is respectively (X V_#1 , Y V_#1 )=(0,0)、(X V_#2 , Y V_#2 )=(D r ,0)、(X V_#3 , Y V_#3 )=(2D r ,0)、(X V_#4 , Y V_#4 )=(D t , D v )、(X V_#5 , Y V_#5 )=(D t +D r , D v )、(X V_#6 , Y V_#6 )=(D t +2D r , D v ).

[0525] For example, the operation example 1 of the direction estimation unit 212 is that the direction of the object is Fig. 20The case of the target object direction (2) shown corresponds to the case where the beam directions of the transmitting antennas Tx#1 and Tx#2 overlap. In this case, the radar transmission signals from both transmitting antennas Tx#1 and Tx#2 are reflected by the target object and received by receiving antennas Rx#1 to Rx#3. Therefore, in this case, the direction estimation unit 212 can use the received signals of the virtual antennas VA#1 to VA#6 corresponding to both Tx#1 and Tx#2 to perform direction estimation.

[0526] exist Fig.23 In the MIMO antenna configuration of (a), Tx#1 has a directional characteristic of beam direction B1, and Tx#2 has a directional characteristic of beam direction B2, which correspond to different beam directions. Fig. 20 As shown, the beam directions of Tx#1 and Tx#2 overlap in an angular region within the range of the beam width. Fig.23 As shown in (a), in the configuration of Tx#1 and Tx#2, as in configuration example A-1, an offset (offset value Dv) is performed in the vertical direction, so when the object exists in the overlapping area of ​​Tx#1 and Tx#2 (for example, Fig. 20 In the case of the target object direction (2) shown in FIG. 1 , the direction estimation unit 212 can measure the angle in the vertical direction in addition to the horizontal direction.

[0527] In addition, if Fig.23 As shown in (a), since the configuration of Tx#1 and Tx#2 is the same as that of configuration example A-2, they are offset in the horizontal direction (offset value Dt), so Fig.23 As shown in (b), in the virtual receiving antenna configuration, the aperture length in the horizontal direction is enlarged. Therefore, in the overlapping area where the target exists in the beam directions of Tx#1 and Tx#2 (for example, Fig. 20 In the case of the target object direction (2) shown in FIG. 1 , the angular resolution is improved in the direction estimation process of the direction estimation unit 212 .

[0528] In addition, Fig.23 In (b), for example, the interval between virtual antennas VA#2 and VA#4, and the interval between virtual antennas VA#3 and VA#5 are Dt-Dr when Dt>Dr, and are Dr-Dt when Dr>Dt. For example, when the absolute value |Dt-Dr| of the difference between the transmitting antenna interval Dt and the receiving antenna interval Dr is set to half a wavelength, in the radar device 10, grating lobes can be suppressed within a field of view angle of ±90°. For example, when Dt=1.5λ and Dr=λ, Dt-Dr=0.5λ. For example, when the field of view angle in the angle measurement detection of the radar device 10 is smaller than the range of ±90°, by setting |Dt-Dr| to about 0.5 to 0.8 wavelengths, the radar device 10 can suppress grating lobes within the field of view angle.

[0529] In addition, the object direction in the operation example 2 of the direction estimation unit 212 is, for example, Fig. 20 The case of the target object direction (1) or target object direction (3) shown corresponds to the area of ​​the beam direction of the transmitting antenna Tx#q. In this case, the radar transmission signal from the transmitting antenna Tx#q is reflected by the target object and received by the receiving antennas Rx#1 to Rx#3.

[0530] Therefore, in this case, for example, when q=1 (the direction of the object is Fig. 20 In the case of the target object direction (1) shown in FIG. 1 ), the direction estimation unit 212 can use the received signals of the virtual antennas VA#1 to VA#3 corresponding to Tx#1 to perform direction estimation. In addition, for example, in the case of q=2 (the target object direction is Fig. 20 In the case of the target direction (3) shown in the figure), the direction estimation unit 212 can use the received signals of the virtual antennas VA#4 to VA#6 corresponding to Tx#2 to perform direction estimation. In the case of operation example 2 of the direction estimation unit 212 of configuration example A-3, the configuration is the same as that of configuration example A-1, and the same effect as that of configuration example A-1 is obtained.

[0531] In the above, the configuration example A has been described.

[0532] [Configuration Example B]

[0533] Configuration example B is a MIMO antenna configuration example when two or more transmission antennas are associated with each transmission beam. In configuration example B, each transmission beam may be composed of two or more transmission antennas.

[0534] Below, as an example, the antenna configuration of a MIMO radar with the number of transmitting antennas Nt=4 (for example, Tx#1, Tx#2, Tx#3, Tx#4) and the number of receiving antennas Na=3 (for example, Rx#1, Rx#2, Rx#3) is described.

[0535] For example, Fig.24 As shown, the transmitting antennas Tx#1 and Tx#3 and the transmitting antennas Tx#2 and Tx#4 have different directivity patterns in terms of transmission beam directions (or directional beam directions). Fig.25 In the example B, Tx#1 and Tx#3 are the directivity patterns of beam direction B1 (beam B1), and Tx#2 and Tx#4 are the directivity patterns of beam direction B2 (beam B2). Fig.24 As shown, the number of transmitting antennas with the directivity pattern having the beam direction B1 and the number of transmitting antennas with the directivity pattern having the beam direction B2 are 2, N B1 =2, N B2 =2.

[0536] In addition, below, the directivity of the receiving antennas (e.g., Rx#1, Rx#2, Rx#3) can be omnidirectional or a directional characteristic that is approximately uniform within the field of view of the transmitting antennas (e.g., Tx#1 to Tx#4) in multiple beam directions.

[0537] For example, when the number of transmission antennas used for multiplex transmission is Nt=4, the radar device 10 uses the Doppler multiplexing number N in the Doppler frequency shift unit 104. DM = 4 Doppler multiplexing signals to transmit radar transmission signals. In this case, for example, in the setting of the above-mentioned Doppler frequency shift amount, N can be applied. B1 =2, N B2 =2 Doppler multiplexing signal allocation.

[0538] Furthermore, for example, virtual reception antenna (or MIMO virtual antenna) configurations VA#1 to VA#12 (not shown) are configured by transmission antennas Tx#1 to Tx#4 and reception antennas Rx#1 to Rx#3.

[0539] In configuration example B, based on the MIMO antenna configuration example of configuration example A, the transmitting antennas of each transmitting beam can be further configured at a position offset in the horizontal direction or the vertical direction, or at a position offset in both the horizontal direction and the vertical direction (for example, offset in the oblique direction).

[0540] Fig.25 An arrangement example of MIMO antennas (Tx#1 to Tx#4, Rx#1 to Rx#3) of arrangement example B is shown.

[0541] Fig.25 (a) represents the configuration example A-1 (for example, Fig.21 The MIMO antenna configuration of (a) is an example of a configuration in which transmitting antennas (for example, Tx#3 and Tx#4) are additionally extended in the horizontal direction in each of the transmitting beams (for example, beam directions B1 and B2).

[0542] in addition, Fig.25 (b) represents the configuration example A-1 (for example, Fig.21 The MIMO antenna configuration of (a) is a configuration example in which transmitting antennas (for example, Tx#3 and Tx#4) are additionally extended in the vertical direction in each of the transmitting beams (for example, beam directions B1 and B2).

[0543] For example, in Fig.25 (a) and Fig.25 In (b), the configuration of the transmitting antennas Tx#1, Tx#2 and the receiving antennas Rx#1 to Rx#3 is the same as Fig.21 The MIMO antenna configuration is the same.

[0544] exist Fig.25 In (a), relative to the transmitting antenna Tx#1, the transmitting antenna Tx#3 is arranged to be offset in the horizontal direction by a spacing amount (e.g., 3Dr) larger than the aperture length (e.g., 2Dr) of the receiving antenna in the horizontal direction. Fig.25 In (a), the transmitting antenna Tx#4 is arranged to be offset in the horizontal direction relative to the transmitting antenna Tx#2 by a spacing amount (for example, 3Dr) that is larger than the aperture length (for example, 2Dr) of the receiving antenna in the horizontal direction.

[0545] pass Fig.25 In the configuration as in (a), the aperture length of the virtual receiving antenna (not shown) is increased, so the angular resolution in the horizontal direction of the radar device 10 is improved.

[0546] In addition, Fig.25 In (b), the transmitting antenna Tx#3 is configured to be offset by 2Dv in the vertical direction relative to the transmitting antenna Tx#1. Fig.25 In (b), the transmitting antenna Tx#4 is configured to be offset by 2Dv in the vertical direction relative to the transmitting antenna Tx#2.

[0547] pass Fig.25 In the configuration (b) of FIG. 1 , the aperture length of the virtual receiving antenna in the vertical direction is enlarged, so that, for example, in the operation example 1 of the direction estimation unit 212, the angular resolution in the vertical direction is improved. Fig.25 For example, in the operation example 2 of the direction estimation unit 212, even if the direction of the target object is Fig.24 In the case of the target object direction (1) shown in FIG. 1 , since the configurations of Tx#1 and Tx#3 are offset in the vertical direction, the direction estimation unit 212 can measure the angle in the vertical direction in addition to the horizontal direction. Fig.24 In the case of the target object direction (3) shown in the figure, since the arrangement of Tx#2 and Tx#4 is offset in the vertical direction, the direction estimation unit 212 can measure the angle in the vertical direction in addition to the horizontal direction.

[0548] In addition, the beam direction and the configuration of the transmitting antenna are not limited to Fig.24 and Fig.25 For example, you can Fig.25 By swapping the configurations of Tx#2 and Tx#3 in (a), you can also Fig.25 (b) The configurations of Tx#2 and Tx#3 are swapped.

[0549] Furthermore, the number of transmission antennas in each beam direction is not limited to two, and the number of transmission antennas in at least one beam direction among a plurality of different beam directions may be three or more.

[0550] In the above, the configuration example B has been described.

[0551] In addition, in configuration examples A and B, the configuration of the receiving antennas (Rx#1 to Rx#3) is described as being arranged at the same position in the vertical direction and being arranged at equal intervals with each antenna being offset by an interval Dr. However, the configuration of the receiving antennas is not limited thereto. For example, in the horizontal configuration of the receiving antennas, the intervals between the receiving antennas may be unequal intervals.

[0552] In addition, for example, instead of making all the receiving antennas at the same vertical position, the vertical positions of some receiving antennas may be offset. For example, the receiving antennas Rx#1 to Rx#3 may be arranged as (X R_#1 , Y R_#1 )=(ax,ay),(X R_#2 , Y R_#2 )=(ax+D r ,ay),(X R_#3 , Y R_#3 )=(ax+2D r , ay+Dv_offset). In this case, in the vertical direction, Rx#3 is offset by Dv_offset (offset, or at a different position) relative to the vertical positions of Rx#1 and Rx#2. In this way, by not making all the vertical positions of the receiving antennas the same, but arranging so that the vertical positions of some receiving antennas are offset, for example, even in the operation example 2 of the direction estimation unit 212, the direction estimation unit 212 can perform angle measurement in the vertical direction in addition to the horizontal direction.

[0553] In addition, for example, instead of making all the receiving antennas have the same vertical position, the receiving antennas may be arranged so that the vertical positions of some receiving antennas are offset and the horizontal positions are the same as the horizontal positions of other receiving antennas. For example, the receiving antennas Rx#1 to Rx#3 are arranged as (X R_#1 , Y R_#1 )=(ax,ay),(X R_#2 , Y R_#2 )=(ax+D r ,ay),(X R_#3 , Y R_#3 )=(ax+D rAt this time, Rx#3 is arranged to be offset (shifted) by Dv_offset in the vertical direction relative to the vertical positions of Rx#1 and #2, and is arranged in the same position in the horizontal direction as the horizontal position of Rx#2.

[0554] In this way, by not making the vertical positions of all the receiving antennas the same position, but configuring them so that the vertical positions of a part of the receiving antennas are offset and the horizontal positions are the same as the horizontal positions of other receiving antennas, for example, even in action example 2 of the direction estimation unit 212, the direction estimation unit 212 can measure angles in the vertical direction in addition to the horizontal direction.

[0555] Here, ax and ay are arbitrary constants, and Dv_offset can be set to a value of about 0.45λ to 0.8λ (for example, a value in the range of 0.5 to 0.8 times the wavelength of the radar transmission signal). Dv_offset can be set, for example, according to the vertical field angle of the radar device 10. For example, in the case of a wide field angle in the range of about ±70 degrees to ±90 degrees in the vertical direction, Dv_offset can be set to about 0.5λ. Alternatively, in the case of a narrow field angle in the range of about ±20 degrees to ±40 degrees in the vertical direction, Dv_offset can be set to about 0.7λ as a wider interval. In this way, by not making the vertical positions of all the receiving antennas the same position, but configuring so that the vertical positions of some of the receiving antennas are offset, for example, even in the operation example 2 of the direction estimation unit 212, the direction estimation unit 212 can measure the angle in the vertical direction in addition to the horizontal direction. In addition, for example, the number of receiving antennas is not limited to three, and may be two, or may be four or more.

[0556] In addition, the MIMO antenna configuration described in Configuration Example A and Configuration Example B is only an example and is not limited to this. For example, it is also possible to further configure other antennas (at least one of the transmitting antenna and the receiving antenna) for the MIMO antenna configuration described in Configuration Example A and Configuration Example B. In addition, it is also possible to configure the antenna in which the horizontal direction and the vertical direction are swapped in Configuration Example A and Configuration Example B. In addition, the spacing between the transmitting antennas described in Configuration Example A and Configuration Example B can be applied to the spacing between the receiving antennas, and the spacing between the receiving antennas described in Configuration Example A and Configuration Example B can be applied to the spacing between the transmitting antennas.

[0557] Alternatively, a MIMO antenna configuration may be a combination of configuration example A and configuration example B. For example, a transmission antenna (the number of antennas is 1) corresponding to one of a plurality of different beam directions may be based on configuration example A, and a transmission antenna (the number of antennas is 2 or more) corresponding to another of a plurality of different beam directions may be based on configuration example B.

[0558] By operating as described above, in multi-beam transmission, the direction estimation unit 212 can perform direction estimation processing in response to the fact that the demultiplexing operation of the Doppler multiplexing and demultiplexing unit 211 differs depending on the target object direction.

[0559] For example, when the Doppler multiplexing and demultiplexing unit 211 is capable of demultiplexing Doppler multiplexed signals from all transmitting antennas (for example, in the case of target direction (2)), the direction estimation unit 212 can improve the angle measurement accuracy and angle measurement resolution by performing direction estimation using the received signals of Nt×Na virtual receiving antennas.

[0560] For example, when the Doppler multiplexing and demultiplexing unit 211 can demultiplex the Doppler multiplexing signal from the transmitting antenna in the beam direction Bq (for example, in the case of the target object direction (1) or (3)), the direction estimating unit 212 uses N Bq The direction of the received signals of ×Na virtual receiving antennas is estimated, which can improve the angle measurement accuracy and angle measurement resolution.

[0561] In the above, an example of the operation of the direction estimation unit 212 has been described.

[0562] As described above, in the present embodiment, the radar device 10 allocates Doppler multiplexing signals (for example, different Doppler frequency shift amount patterns) that satisfy at least condition 1 and are different between multi-beams in the Doppler frequency shift unit 104 in a multi-beam transmission MIMO radar using non-equally spaced Doppler multiplexing. As a result, in the radar device 10, even when the difference in reception levels between reflected waves corresponding to transmission antennas having different directional characteristics is large, the transmission antenna can be identified in the Doppler multiplexing demultiplexing unit 211, and Doppler multiplexing demultiplexing can be performed. Therefore, according to the present embodiment, it is possible to suppress degradation of target detection performance, misestimation of Doppler frequency, or degradation of angle measurement performance.

[0563] In addition, for example, when the aforementioned conditions 1 and 2 are satisfied in the allocation of the Doppler multiplexed signal in the Doppler frequency shift unit 104, in the radar device 10, even when the difference in reception levels between reflected waves corresponding to transmitting antennas having different directional characteristics is large, the detectable Doppler frequency range fd is within the range of -1 / (2Tr)≦fd<1 / (2Tr), and can be expanded to the same Doppler frequency range as that when a single transmitting antenna is used.

[0564] In addition, in the radar device 10 of the present embodiment, as a multi-beam transceiver MIMO radar structure, Doppler multiplexing demultiplexing can be performed without using the following beam direction determination processing, thereby reducing the amount of reception processing calculation. The beam direction determination processing is a processing using a directional receiving antenna (or a directional receiving processing using a receiving array antenna).

[0565] In addition, for example, when receiving antennas with different beam directions are used as receiving antennas in a multi-beam transmission and reception MIMO radar structure, the number of receiving antennas available for angle measurement may decrease depending on the target object direction, and thus the angle measurement accuracy or angle measurement resolution of the radar device 10 may decrease. In the present embodiment, for example, it is possible to perform demultiplexing of Doppler multiplexing regardless of the target object direction without using a directional receiving antenna, thereby suppressing the decrease in angle measurement accuracy and angle measurement resolution.

[0566] Therefore, according to the present embodiment, the detection performance of the multi-beam transmission MIMO radar using non-uniformly spaced Doppler multiplexing transmission can be improved.

[0567] (Variant 1)

[0568] In the first modification, in the case where the number of transmission antennas corresponding to different beam directions in multi-beam transmission is one (for example, N B1 =N B2 =1, Nt=2) is used to illustrate the case.

[0569] For example, the Doppler frequency shift unit 104 may provide a plurality of phase rotations φ for generating a Doppler multiplexed signal to one of the plurality of transmitting antennas. n (m) For example, the number of Doppler shift amounts assigned to a certain one of the plurality of transmission antennas may be set to be plural.

[0570] In the following, we will consider N in the beam direction Bq Bq = 1 transmitting antenna, the number of Doppler multiplexing signals generated in the Doppler frequency shift unit 104 is expressed as “Doppler multiplexing signal number N DOP(Bq) Here, q = 1 or 2. As an example, the number of transmitting antennas in the beam direction B2 in the setting example 1 of the Doppler frequency shift amount is N. B2 =1, the number of Doppler multiplexing signals is N DOP(B2) =1.

[0571] For example, by satisfying the following condition 1 (4), an effect equivalent to condition 1 (2) can be obtained.

[0572] <Condition 1>

[0573] (4) The number of Doppler multiplexed signals in each beam direction is different (N DOP(B1) ≠N DOP(B2) But only in N B1 =N B2 =1 time).

[0574] For example, the number of Doppler multiplexed signals (or the number of Doppler frequency shifts allocated) generated by the transmitting antenna in the beam direction B1 is N. DOP(B1) The number of Doppler multiplexed signals (or the number of Doppler frequency shift amounts allocated) N generated by the transmitting antenna for the beam direction B2 DOP(B2) It can be different. By setting (4) of condition 1, the number of transmitting antennas N t =2, Doppler multiplexing number N DDM =2, even when there is a large difference in reception levels between reflected waves corresponding to transmission antennas in different beam directions, Doppler multiplexing can be demultiplexed in the same manner as in the above-described embodiment.

[0575] Next, an example of setting the Doppler shift amount in the Doppler shift unit 104 will be described.

[0576] <Doppler shift amount setting example 5>

[0577] Fig.26 Indicates the number of transmitting antennas Nt = 2, N B1 =1,N B2 =1 is an example of setting the pattern of the Doppler shift amount for the transmission Doppler frequency. Fig.26 , Tx#1 is a transmitting antenna of a beam direction B1 (eg, a transmitting antenna that forms the transmitting beam B1), and Tx#2 is a transmitting antenna of a beam direction B2 (eg, a transmitting antenna that forms the transmitting beam B2).

[0578] In addition, in the setting example 5 of the Doppler frequency shift amount, if Fig.26 As shown, the basic unit of the Doppler frequency shift interval in the Doppler frequency shift unit 104 is set to Δfd=1 / (Tr×(N DM +δ))=1 / (4Tr), and δ=1, but the value of δ is not limited to this. δ can be a positive integer or a positive real number.

[0579] exist Fig.26 In the example shown, N for beam direction B1 B1 = 1 transmitting antenna Tx#1, the number of Doppler multiplexed signals generated in the Doppler frequency shift unit 104 is N DOP(B1) = 1, N relative to beam direction B2 B2 = 1 transmitting antenna Tx#2, the number of Doppler multiplexed signals generated in the Doppler frequency shift unit 104 is NDOP(B2) =2.

[0580] exist Fig.26 In the example shown, the first and second Doppler shift units 104 (or Doppler shift units 104 - 1 and 104 - 2 ) can perform the following operations.

[0581] For example, in order to give the Doppler shift amount DOP1=-1 / (2Tr) to the first transmitting antenna Tx#1, the first Doppler shift unit 104 gives a phase rotation of Φ1(m)=2πDOP1×(m-1)Tr=-π(m-1) according to the transmission period Tr of the chirp signal and outputs it.

[0582] The second Doppler frequency shift unit 104 generates two Doppler multiplexed signals for the second transmission antenna Tx#2, for example. Fig.26 In the example of 2-1 =-1 / (4Tr) and Doppler frequency shift DOP 2-2 =1 / (4Tr). The second Doppler frequency shift unit 104 provides two Doppler frequency shift amounts DOP to the second transmission antenna Tx#2. 2-1 and DOP 2-2 , and according to the transmission period Tr of the chirp signal, a phase rotation Φ2(m)=phseq[mod(m,4)+1] is given and output.

[0583] Here, phseq[ps] represents the psth element of PhaseSeq = [0, 0, π, π]. For example, phseq[1] = phseq[2] = 0, phseq[3] = phase[4] = π. In addition, mod(x, y) is a modulo function representing the remainder when x is divided by y. In addition, since two Doppler multiplexed signals are generated for the transmitting antenna Tx#2, the power is divided into the power for the Doppler frequency shift amount DOP. 2-1 and for the Doppler frequency shift DOP 2-2 There are 2 copies in total.

[0584] Hereinafter, the interval between the Doppler frequency shift amounts given to Tx#n1 and Tx#n2 is expressed as the Doppler frequency shift interval “Δfd (n1，n2) ”.

[0585] In addition, if Fig.26 As shown, the Doppler frequency shift DOP will be given 2-1 Tx#2 is expressed as "Tx#2-1" and will be given a Doppler frequency shift DOP 2-2 Tx#2 is expressed as "Tx#2-2".

[0586] exist Fig.26In the example, the interval (Doppler shift interval) of the Doppler frequency shift amount given to each transmitting antenna Tx#1 and Tx#2 (for example, Tx#2-1, Tx#2-2) is Δfd (1，2-1) =Δfd,Δfd (2-1，2-2) =2Δfd,Δfd (2-2，1) =Δfd. Therefore, Fig.26 The intervals of the Doppler frequency shift amounts given to the respective transmission antennas in the transmission antenna number Nt=2 are not all the same, but include unequal intervals (Δfd (1，2-1) =Δfd (2-2，1) ≠Δfd (2-1，2-2) ), so it is unequally spaced Doppler multiplexing transmission (unequally spaced DDM transmission).

[0587] In addition, Fig.26 In the example, the number of transmitting antennas in the beam direction B1 is N. B1 =1, the number of Doppler multiplexing signals N DOP(B1) =1, which means that the transmission antennas in the beam direction B1 do not form a relationship for Doppler multiplexing transmission.

[0588] In addition, Fig.26 In the example, the number of transmitting antennas in the beam direction B2 is N. B2 =1, the number of Doppler multiplexing signals N DOP(B2) =2. In addition, Fig.26 The interval of the Doppler frequency shift between the transmitting antennas Tx#2-1 and Tx#2-2 in the beam direction B2 is Δfd (2-1，2-2) =Δfd (2-2，2-1) =2Δfd Therefore, the intervals of the Doppler frequency shift amounts given to the transmission antennas in the beam direction B2 are all the same, and this is equal-interval Doppler multiplexing transmission (equal-interval DDM transmission).

[0589] therefore, Fig.26 The example shown is a setting example of a pattern of the Doppler shift amount that does not satisfy condition 2.

[0590] In addition, Fig.26 In the example shown, N DOP(B1) ≠N DOP(B2) , N B1 =N B2 =1, so Fig.26 The example shown is an example of setting the pattern of the Doppler shift amount that satisfies condition 1 (4).

[0591] For example, when the target object direction is the beam direction B1 and the target object direction is the beam direction B2, the radar device 10 receives different numbers of Doppler multiplexed signals (for example, the number of Doppler multiplexed signals satisfying condition 1 (4)) depending on the target object direction, as in setting example 1. Thus, the radar device 10 can determine in the Doppler multiplexing and demultiplexing unit 211, for example, whether a decrease in the reception level of the received signal corresponding to the transmitting antenna in the beam direction B1 or a decrease in the reception level of the received signal corresponding to the transmitting antenna in the beam direction B2 has occurred, based on the peak value of the detected Doppler frequency (for example, the number of peaks).

[0592] In addition, for example, the transmitting antenna in the beam direction B1 is a single antenna transmission (N B1 =1), the number of Doppler multiplexed signals N DOP(B1) =1. Therefore, for example, when the Doppler multiplexing and demultiplexing unit 211 determines that the received signal is a received signal corresponding to the transmitting antenna in the beam direction B1, the radar device 10 may not perform demultiplexing processing on the Doppler multiplexed signal of the received signal in the beam direction B1. By the operation of the Doppler multiplexing and demultiplexing unit 211, the radar device 10 can determine the Doppler frequency fd of the target object in the range of -1 / (2Tr)≦fd<1 / (2Tr), and can obtain an output that corresponds to the transmitting antenna for each Doppler multiplexed signal.

[0593] For example, the Doppler multiplex signal number N of the Doppler multiplex signal transmitted from the transmission antenna in the beam direction B2 is DOP(B2) =2, and the Doppler frequency shift interval that does not satisfy condition 2 and becomes an equally spaced Doppler multiplexed signal is Doppler multiplexed and transmitted. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is a received signal corresponding to the transmitting antenna of the beam direction B2, the radar device 10 can demultiplex the Doppler multiplexed signal using the existing demultiplexing operation of the Doppler multiplexed signal. In addition, the radar device 10 can determine the Doppler frequency fd of the target object in the range of -1 / (4Tr)≦fd<1 / (4Tr), and can obtain an output that corresponds to the transmitting antenna for each Doppler multiplexed signal.

[0594] In addition, for example, when the target object direction is the middle direction between the beam direction B1 and the beam direction B2, and the target object direction is in the direction of the region where the beam widths of the two beams overlap by about 3 dB or 6 dB (for example, Fig.13In the target direction (2) shown in the figure, the reception level of the reception signal corresponding to Tx#1 of beam direction B1 and the reception level of the reception signal corresponding to Tx#2 of beam direction B2 are about the same. Therefore, the signals transmitted from Nt transmission antennas including the transmission antennas of beam direction B1 and beam direction B2 are Doppler multiplexed and transmitted using the Doppler frequency shift interval that becomes non-uniformly spaced Doppler multiplexing. Therefore, the radar device 10 can demultiplex the Doppler multiplexed signal based on the demultiplexing operation of the existing Doppler multiplexed signal. Through the operation of such a Doppler multiplexing demultiplexing unit 211, the radar device 10 can determine the Doppler frequency fd of the target in the range of -1 / (2Tr)≦fd<1 / (2Tr), and can obtain an output that corresponds to the transmission antenna for each Doppler multiplexed signal.

[0595] In addition, the example of generating two Doppler multiplexed signals for one transmission antenna is not limited to Fig.26 The example shown, for example, in Fig. 27 In the setting example shown, a plurality of Doppler multiplexed signals can be generated in the same manner.

[0596] exist Fig. 27 In the example shown, the first and second Doppler shift units 104 (or Doppler shift units 104 - 1 and 104 - 2 ) can perform the following operations.

[0597] For example, in order to give the Doppler shift amount DOP1=1 / (4Tr) to the first transmitting antenna Tx#1, the first Doppler shift unit 104 gives a phase rotation of Φ1(m)=2πDOP1×(m-1)Tr=π(m-1) / 2 according to the transmission period Tr of the chirp signal and outputs it.

[0598] The second Doppler frequency shift unit 104 generates two Doppler multiplexed signals for the second transmission antenna Tx#2, for example. Fig. 27 In the example of 2-1 =-1 / (2Tr) and Doppler frequency shift DOP 2-2 = 0. The second Doppler frequency shift unit 104 provides two Doppler frequency shift amounts DOP to the second transmission antenna Tx#2. 2-1 and DOP 2-2 , and according to the transmission period Tr of the chirp signal, a phase rotation Φ2(m)=phseq[mod(m,4)+1] is given and output.

[0599] Here, phseq[ps] represents the psth element of PhaseSeq = [0, π / 2, 0, π / 2]. For example, phseq[1] = phseq[3] = 0, phseq[2] = phase[4] = π / 2. In addition, mod(x, y) is a modulo function representing the remainder when x is divided by y. In addition, since two Doppler multiplexed signals are generated for the transmitting antenna Tx#2, the power is divided into the power used for the Doppler frequency shift amount DOP. 2-1 and for the Doppler frequency shift DOP 2-2 There are 2 copies in total.

[0600] In addition, examples of generating two Doppler multiplexed signals are not limited to the above examples. For example, two Doppler multiplexed signals can also be generated using PhaseSeq = [0, -π / 2, 0, -π / 2], [π, -π / 2, π, -π / 2] or [π, π / 2, π, π / 2].

[0601] In addition, the Doppler frequency shift unit 104 may allocate a fixed Doppler frequency shift amount to the transmission antenna, or may allocate the Doppler frequency shift amount variably according to the transmission cycle. For example, the Doppler frequency shift unit 104 may perform the Doppler frequency shift in the odd-numbered transmission cycles. Fig. 27 The distribution of the Doppler frequency shift amount shown is performed in the even-numbered transmission cycles. Fig.28 The distribution of Doppler frequency shift is shown.

[0602] exist Fig.28 In the example of setting the Doppler frequency shift amount shown in the figure, the application Fig. 27 In the setting of the Doppler frequency shift amount shown, the allocation of the Doppler frequency shift amount to the beam direction B1 and the allocation of the Doppler frequency shift amount to the beam direction B2 are swapped.

[0603] In this case, the radar device 10 can perform the processing of the Doppler analysis unit 209 using the chirp signal of the odd-numbered transmission period (for example, VFFT1) and the processing of the Doppler analysis unit 209 using the chirp signal of the even-numbered transmission period (for example, VFFT2). For example, the radar device 10 can determine the presence or absence of aliasing in the Doppler range ±1 / (4Tr) by detecting the phase difference between the FFT peaks based on VFFT1 and based on VFFT2.

[0604] (Variant 2)

[0605] In the above embodiment, the case where the number of multi-beams NB=2 is described, but the number of multi-beams NB may be greater than or equal to 3. In Modification 2, the case where the number of multi-beams NB>2 is described.

[0606] When the number of multi-beams NB>2, the Doppler frequency shift unit 104 may apply the conditions 1a and 2a described later instead of the above conditions 1 and 2 to give a predetermined phase rotation Φ with different Doppler frequency shift amounts to each transmitting antenna. n Thus, similarly to the above-described embodiment, even when the received power levels of the received signals (reflected waves) corresponding to the transmitting antennas in different beam directions are greatly different, the radar device 10 can demultiplex the Doppler multiplexed signal, thereby suppressing the degradation of the positioning performance and the radar detection performance.

[0607] Hereinafter, conditions 1a and 2a regarding the Doppler shift amount given by the Doppler shift unit 104 when the multi-beam number NB>2 will be described.

[0608] The radar device 10 is, for example, a multi-beam transmission MIMO radar using Nt transmission antennas Tx#1 to Tx#Nt including transmission antennas with different beam directions, and can use the Nt transmission antennas Tx#1 to Tx#Nt to perform non-uniformly spaced Doppler multiplexing transmission. For example, the Doppler frequency shift unit 104 can give the Nt transmission antennas a non-uniformly spaced Doppler frequency shift.

[0609] Furthermore, the radar device 10 can use Doppler multiplexing transmission that satisfies the following condition 1a, for example, to multiplex and transmit radar transmission signals simultaneously from Nt transmission antennas Tx# 1 to Tx#Nt.

[0610] Here, let the number of transmitting antennas N for each beam direction Bq be Bq ≧1. In addition, let the number of transmitting antennas Nt≧2NB-1, and let the number of Doppler multiplexing N DDM ≧2NB-1. In the following description, the number of transmitting antennas N in each beam direction Bq is Bq Also recorded as N B(q) (For example, N Bq =N B(q) ).

[0611] For example, the case of Nt=2NB-1 is the case where the number of transmitting antennas Nt is the smallest, which is the case where, among the transmitting antennas in each beam direction Bq, the number of transmitting antennas in one beam direction is 1 and the number of transmitting antennas in the other beam directions is 2.

[0612] In addition, the total number of transmission antennas in each beam direction Bq is Nt. For example, the radar device 10 may allocate one Doppler multiplexing signal to one transmission antenna. In this case, the Doppler multiplexing number N DDM Equal to Nt.

[0613] <Condition 1a>

[0614] N allocated to the qth beam direction B(q) B(q) N transmitting antennas B(q) The Doppler multiplexed signals satisfy one of the following conditions: Here, q = 1, ..., NB.

[0615] (1) The Doppler intervals included in the Doppler multiplexing signals of the transmitting antennas assigned to the beam directions with the same Doppler multiplexing number are different (1-i); or, when the Doppler multiplexing number is 3 or more, the Doppler intervals included are the same, but the order of these Doppler frequency shift intervals is different (for example, even if one of the Doppler frequency shift intervals corresponding to each beam direction is cyclically shifted on the Doppler frequency axis, there will be no consistency) (1-ii).

[0616] (2) The Doppler multiplexing number is different between all beam directions.

[0617] For example, in the case where the Doppler multiplexing numbers of the beam directions B(a), B(b), and B(c) are the same among NB multi-beams (for example, N B(a) =N B(b) =N B(c) , where N B(a) ≧2, N B(b) ≧2, N B(c) Here, a, b, and c are integers in the range of 1 to NB, and represent beam directions with the same Doppler multiplexing number.

[0618] At this time, when the Doppler intervals included between the Doppler multiplexed signals assigned to the beam direction B(a) and the beam direction B(b), between the Doppler multiplexed signals assigned to the beam direction B(b) and the beam direction B(c), and between the Doppler multiplexed signals assigned to the beam direction B(c) and the beam direction B(a) are different, condition 1a (1-i) is satisfied. In addition, for example, when the Doppler multiplexing number is 3 or more, the Doppler intervals of the beam directions B(a), B(b), and B(c) are the same but the order of these Doppler frequency shift intervals is different (for example, even if the Doppler frequency shift interval of one of B(a), B(b), and B(c) is cyclically shifted in the Doppler frequency domain, it will not coincide with the other Doppler frequency shift intervals), condition 1a (1-ii) is satisfied.

[0619] In addition, for example, the Doppler multiplexing number (N) of the transmission antennas assigned to NB beam directions B(1), B(2), ..., B(NB) as multi-beams is B(1) , N B(2) ,…,N B(NB) ) are different from each other, condition 1a (2) is satisfied.

[0620] Furthermore, the radar device 10 may use Doppler multiplexing transmission that further satisfies the following condition 2a, for example, and may multiplex and transmit radar transmission signals simultaneously from the Nt transmission antennas Tx#1 to Tx#Nt.

[0621] <Condition 2a>

[0622] N for beam direction Bq B(q) transmit antennas to achieve unequally spaced Doppler multiplexing (but only in N Bq ≧2) method, the Doppler multiplexing signal is allocated to the transmitting antenna in the beam direction Bq.

[0623] By satisfying condition 2a, the Doppler frequency range fd detectable by the radar device 10 reaches the range of -1 / (2Tr)≦fd<1 / (2Tr), which can be expanded to a larger range than the Doppler detection range of the existing equally spaced Doppler multiplexing -1 / (2Nt Tr)≦fd<1 / (2Nt Tr).

[0624] Even when condition 1a is satisfied but condition 2a is not, the Doppler frequency range fd detectable by the radar device 10 can be expanded to a larger range than the Doppler detection range of the conventional equally spaced Doppler multiplexing -1 / (2Nt Tr)≦fd<1 / (2Nt Tr).

[0625] In addition, conditions 1a and 2a are conditions for beams with overlapping field of view angles (FOV) between beam directions. In the case of beams with overlapping field of view angles between beam directions, the following conditions 1b and 2b may be applied, which include Doppler multiplexing signals (hereinafter referred to as "Doppler multiplexing signals of overlapping beam directions") of transmitting antennas assigned to beam directions with overlapping field of view angles (hereinafter referred to as "overlapping beam directions").

[0626] For example, when the field of view angles of beam direction B(1) and beam direction B(2) overlap, the Doppler multiplexed signal of the overlapping beam direction refers to the Doppler multiplexed signals respectively assigned to beam direction B(1) and beam direction B(2), and the Doppler multiplex number is N. B(1) +N B(2) .

[0627] <Condition 1b>

[0628] N allocated to the qth beam direction B(q) B(q) N transmitting antennas B(q) The Doppler multiplexed signals satisfy one of the following conditions: Here, q = 1, ..., NB.

[0629] (1) The Doppler intervals included in the Doppler multiplexing signals assigned to the transmitting antennas with the same beam direction or overlapping beam direction having the same Doppler multiplexing number are different (1-i); or, when the Doppler multiplexing number is 3 or more, the Doppler intervals included are the same, but the order of these Doppler frequency shift intervals is different (for example, even if one of the Doppler frequency shift intervals corresponding to each beam direction or overlapping beam direction is cyclically shifted on the Doppler frequency axis, there will be no consistency) (1-ii).

[0630] (2) The Doppler multiplexing number is different between all beam directions and between overlapping beam directions.

[0631] <Condition 2b>

[0632] The result is non-uniformly spaced Doppler multiplexing of transmit antennas based on beam direction Bq and transmit antennas based on overlapping beam directions (but only in N Bq ≧2) method to distribute Doppler multiplexing signals.

[0633] By satisfying condition 2b, the detectable Doppler frequency range fd in the radar device 10 reaches the range of -1 / (2Tr)≦fd<1 / (2Tr). In addition, even when condition 1b is satisfied but condition 2b is not satisfied, the detectable Doppler frequency range fd in the radar device 10 can be expanded to a larger range than the Doppler detection range of -1 / (2Nt Tr)≦fd<1 / (2Nt Tr) of the existing equally spaced Doppler multiplexing.

[0634] Hereinafter, as an example, an operation example when NB=3 will be described.

[0635] <Action Example 1>

[0636] In operation example 1, an operation example in the case of NB=3 and no overlapping beam directions will be described.

[0637] Fig.29 An example of a beam pattern of beam directions B1, B2, and B3 when the number of multi-beams NB = 3 and there is no overlapping beam direction is shown. Fig.29 As shown, when there is no overlapping portion of the beam patterns (or when there is little overlapping portion), conditions 1a and 2a can be applied.

[0638] For example, in Fig.29In the case where the target object direction is any one of the beam direction B1, beam direction B2 and beam direction B3, by making the distribution of the Doppler multiplexed signal performed by the Doppler frequency shift unit 104 satisfy the condition 1a, the radar device 10 can determine in the Doppler multiplexing demultiplexing unit 211 whether a reduction in the reception level of the reception signal corresponding to the transmitting antenna in the beam direction B1, a reduction in the reception level of the reception signal corresponding to the transmitting antenna in the beam direction B2, or a reduction in the reception level of the reception signal corresponding to the transmitting antenna in the beam direction B3 has occurred.

[0639] In addition, for example, by making the allocation of Doppler multiplexed signals performed by the Doppler frequency shift unit 104 satisfy condition 2a, the Doppler multiplexed signals transmitted from the transmitting antenna in beam direction B1 (or B2, B3) are Doppler multiplexed and transmitted using the Doppler frequency shift interval that becomes non-uniformly spaced Doppler multiplexing.

[0640] Therefore, for example, when the Doppler multiplexing and demultiplexing unit 211 determines that the received signal is a received signal corresponding to the transmission antenna in the beam direction B1 (or B2, B3), the radar device 10 can demultiplex the Doppler multiplexed signal using the existing demultiplexing operation of the Doppler multiplexed signal. By the operation of the Doppler multiplexing and demultiplexing unit 211, the radar device 10 can determine the Doppler frequency fd of the target object in the range of -1 / (2Tr)≦fd<1 / (2Tr), and can obtain an output that corresponds to the transmission antenna for each Doppler multiplexed signal.

[0641] <Action Example 2>

[0642] In operation example 2, an operation example when NB=3 and there are overlapping beam directions is described.

[0643] Fig.30 This shows an example of a beam pattern of beam directions B1, B2, and B3 when the number of multi-beams NB = 3 and there are overlapping beam directions. Fig.30 As shown, when there are overlapping portions of beam patterns (or when there are many overlapping portions), conditions 1b and 2b can be applied.

[0644] For example, in Fig.30 In the case where the target direction is one of the beam direction B1, beam direction B2, and beam direction B3 that are different from the overlapping beam range ( Fig.30In the case of one of the target object directions (1), (3), and (5) shown in the figure), by making the distribution of the Doppler multiplexed signal performed by the Doppler frequency shift unit 104 satisfy the condition 1b, the radar device 10 can determine in the Doppler multiplexing and demultiplexing unit 211 whether the received signal is a received signal corresponding to the transmitting antenna in the beam direction B1, a received signal corresponding to the transmitting antenna in the beam direction B2, or a received signal corresponding to the transmitting antenna in the beam direction B3.

[0645] In addition, for example, Fig.30 In the case where the direction of the target object is within the overlapping beam range ( Fig.30 In the case of the target direction (2) or (4) shown in the figure), by making the distribution of the Doppler multiplexed signal performed by the Doppler frequency shift unit 104 satisfy the condition 1b, the radar device 10 can determine in the Doppler multiplexing demultiplexing unit 211 whether the received signal corresponds to the transmitting antenna of the beam directions B1 and B2 or the receiving signal corresponds to the transmitting antenna of the beam directions B2 and B3.

[0646] In addition, for example, by making the allocation of Doppler multiplexed signals by the Doppler frequency shift unit 104 satisfy the condition 2b, the Doppler multiplexed signals transmitted from the transmission antennas in the beam direction B1 (or B2, B3) are Doppler multiplexed and transmitted using the Doppler frequency shift intervals that become non-uniformly spaced Doppler multiplexing. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is a received signal corresponding to the transmission antennas in the beam direction B1 (or B2, B3), the radar device 10 can demultiplex the Doppler multiplexed signal using the existing demultiplexing operation of the Doppler multiplexed signal. Through the operation of the Doppler multiplexing demultiplexing unit 211, the radar device 10 can determine the Doppler frequency fd of the target object in the range of -1 / (2Tr)≦fd<1 / (2Tr), and can obtain an output that corresponds to the transmission antennas for each Doppler multiplexed signal.

[0647] In addition, for example, by making the allocation of Doppler multiplexed signals by the Doppler frequency shift unit 104 satisfy the condition 2b, the Doppler multiplexed signals transmitted from the transmission antennas of the beam directions B1 and B2 (or the beam directions B2 and B3) are Doppler multiplexed and transmitted using the Doppler frequency shift intervals that become non-uniformly spaced Doppler multiplexed. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is a received signal corresponding to the transmission antennas of the beam directions B1 and B2 (or the beam directions B2 and B3), the radar device 10 can demultiplex the Doppler multiplexed signal using the existing demultiplexing operation of the Doppler multiplexed signal. Through the operation of the Doppler multiplexing demultiplexing unit 211, the radar device 10 can determine the Doppler frequency fd of the target object in the range of -1 / (2Tr)≦fd<1 / (2Tr), and can obtain an output that corresponds to the transmission antenna for each Doppler multiplexed signal.

[0648] (Variant 3)

[0649] In the above-mentioned embodiments and modifications, Fig.13 , Fig. 20 , Fig.24 , Fig.29 and Fig.30 As shown in the figure, the case where the beam directions of the multi-beams are different from each other has been described, but the setting of the multi-beams (for example, the beam direction and the beam width) is not limited to the above example.

[0650] For example, at least one of the beam direction and the beam width of each beam constituting the multi-beam may be different. Also, the number of multi-beams NB≧2 may be satisfied.

[0651] Next, a multi-beam setting example is described.

[0652] <Multi-beam setting example 1>

[0653] In setting example 1, for example, it can be as follows Fig.31 As shown, in the multi-beam (e.g., beam directions B1, B2, B3), the beam directions are different from each other and the beam widths are different. It may be that in the multi-beam (e.g., beam directions B1, B2, B3), the beam directions in the horizontal direction (or horizontal plane) are different from each other and the beam widths in the horizontal direction (or horizontal plane) are different. It may also be that the beam directions in the vertical direction (or vertical plane) are different from each other and the beam widths in the vertical direction (or vertical plane) are different.

[0654] <Multi-beam setting example 2>

[0655] In the above embodiment, Fig.13 As shown, an example in which the beam directions are different in the horizontal direction (or horizontal plane) is described, but the present invention is not limited to this.

[0656] In setting example 2, for example, the beam directions may be different in the vertical direction (or vertical plane).

[0657] For example, it could be, Fig.32 As shown in (a), in the multi-beam (for example, beam directions B1 and B2), the beam directions are substantially the same in the horizontal direction (or horizontal plane), and are different in the vertical direction (or vertical plane).

[0658] In addition, for example, it can also be Fig.32 As shown in (b), in the multi-beam (for example, beam directions B1, B2, B3), the beam directions are different in both the horizontal direction (or horizontal plane) and the vertical direction (or vertical plane).

[0659] <Multi-beam setting example 3>

[0660] In setting example 3, for example, it can be as follows Fig.33 As shown, in the multi-beam (for example, beam directions B1 and B2), the beam directions are the same but the beam widths are different. Alternatively, in the multi-beam (for example, beam directions B1 and B2), the beam directions in the horizontal direction (or horizontal plane) are the same but the beam widths in the horizontal direction (or horizontal plane) are different. Alternatively, in the multi-beam (for example, beam directions B1 and B2), the beam directions in the vertical direction (or vertical plane) are the same but the beam widths in the vertical direction (or vertical plane) are different.

[0661] In setting example 3, for example, in the description of the above embodiment, "transmitting antennas with different beam directions" are replaced with "transmitting antennas with different beam widths" (hereinafter referred to as "different beams"), thereby enabling the same application as the above embodiment.

[0662] Hereinafter, as an example, the operation example of the radar device 10 in the case where the beam directions are the same but the beam widths are different is described using the setting example 1 of the Doppler frequency shift amount. In addition, the setting of the Doppler frequency shift amount is not limited to the setting example 1, and the same operation can be performed even when other setting examples of the Doppler frequency shift amount are used, and the same effect as the above-mentioned embodiment can be obtained.

[0663] For example, when the number of transmitting antennas Nt=3 (for example, Tx#1, Tx#2, Tx#3), N B1 =2, N B2 =1, the above-mentioned Doppler frequency shift setting example 1 is applied. In addition, for example, Tx#1 and Tx#2 are Fig.33 The transmit antenna of beam width B1 (eg, beam B1) shown, Tx#3 is Fig.33The transmit antenna has a beam width B2 (eg, beam B2) as shown. Fig.33 , an example of a case where the beam width of beam B1 is wider than the beam width of beam B2 is shown. Here, the beam widths of beams B1 and B2 may be in the horizontal direction (or horizontal plane), in the vertical direction (or vertical plane), or in both the horizontal direction (or horizontal plane) and the vertical direction (or beam), and the same effect can be obtained.

[0664] In the radar device 10 , the receiving antenna may be an omnidirectional antenna (or an antenna having a directional characteristic that is substantially uniform within the field of view covered by the transmitting antennas of both the beam B1 and the beam B2 ).

[0665] For example, when the object position is Fig.33 In the case of the target object position (1) or the target object position (3) shown, the target object position is within the beam width of beam B1 and within the field of view, so the reception level of the reflected wave corresponding to the radar transmission wave transmitted from Tx#1 and Tx#2 of beam B1 is relatively high. On the other hand, since the target object position (1) and the target object position (3) are outside the beam width of beam B2 and outside the field of view, the radiation direction of the radar transmission wave transmitted from Tx#3 of beam B2 does not coincide with the direction of the target object positions (1) and (3), and the target object position (1) and the target object position (3) are equivalent to the zero azimuth of the transmission antenna Tx#3 of beam B2. Therefore, the reception level of the reception signal corresponding to Tx#3 in the radar device 10 is lower than the reception level of the reception signal corresponding to Tx#1 and Tx#2. For example, the reception level of the received signal corresponding to Tx#3 is greatly different from the reception level of the received signals corresponding to Tx#1 and Tx#2, and may be 10 dB or more lower depending on the beam directivity characteristics of the null azimuth of Tx#3. In this case, the received signal received by the radar device 10 becomes Fig.12 The received signal shown in (a).

[0666] In addition, for example, at the object position such as Fig.33 When the target object position (4) shown in FIG. 1 is in an area where the field of view angles of beams B1 and B2 overlap (for example, when located at a close distance), radar device 10 receives reflected waves corresponding to radar transmission waves transmitted from Tx#1 and Tx#2 of beam B1, and reflected waves corresponding to radar transmission waves transmitted from Tx#3 of beam B2. In this case, the received signal received by radar device 10 may be, for example, Fig.12 In addition, for example, when the directional gain of beam B2 is higher than that of beam B1 by about 10 dB, the received signal received by radar device 10 may be, for example, Fig.12The received signal is as shown in (c).

[0667] In addition, for example, at the object position such as Fig.33 When the target object position (2) is located within the field of view of beam B2 and outside the field of view of beam B1 (for example, when it is located at a long distance), the reception level of the reflected wave corresponding to the radar transmission wave sent from Tx#3 of beam B2 is relatively high. On the other hand, since the directional gain of beam B1 is smaller than the directional gain of beam B2, the reception level of the reflected wave corresponding to the radar transmission wave sent from Tx#1 and Tx#2 of beam B1 is lower than the reception level of the received signal corresponding to Tx#3. For example, the reception level of the received signal corresponding to Tx#1 and Tx#2 is greatly different from the reception level of the received signal corresponding to Tx#3, and depends on the beam directivity characteristics of Tx#1 and Tx#2, and may be, for example, 10 dB or more lower. In such a case, the received signal received by radar device 10 becomes Fig.12 The received signal shown in (c).

[0668] For example, Fig.12 As shown in (b), when the radar device 10 receives the reception signals corresponding to the transmission antennas of each beam at substantially the same reception level, the signals transmitted from the Nt transmission antennas including the transmission antennas of the beams B1 and B2 are Doppler multiplexed and transmitted using the Doppler frequency shift intervals that become non-uniformly spaced Doppler multiplexing. Therefore, the radar device 10 can demultiplex the Doppler multiplexed signal based on the existing demultiplexing operation of the Doppler multiplexed signal.

[0669] In addition, if Fig.12 (a) and Fig.12 As shown in (c), when receiving the reflected wave from one of the beam B1 and the beam B2 (when the difference in reception level is large), the radar device 10 receives different Doppler multiplexed signals (for example, Doppler multiplexed signals satisfying condition 1) depending on the position of the target object. Therefore, the radar device 10 can determine in the Doppler multiplexing and demultiplexing unit 211 whether a decrease in the reception level of the reception signal corresponding to the transmission antenna of the beam B1 or a decrease in the reception level of the reception signal corresponding to the transmission antenna of the beam B2 has occurred.

[0670] For example, the Doppler multiplexed signal transmitted from the transmission antenna of the beam B1 is Doppler multiplexed and transmitted using the Doppler frequency shift interval that is non-uniformly spaced Doppler multiplexing. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is a received signal corresponding to the transmission antenna of the beam B1, the radar device 10 can demultiplex the Doppler multiplexed signal based on the existing demultiplexing operation of the Doppler multiplexed signal.

[0671] In addition, for example, the transmission antenna of beam B2 is a single antenna transmission. Therefore, for example, when the Doppler multiplexing and demultiplexing unit 211 determines that the received signal is a received signal corresponding to the transmission antenna of beam B2, the radar device 10 does not need to perform the demultiplexing process on the Doppler multiplexing signal of the received signal of beam B2.

[0672] By operating the Doppler multiplexing and demultiplexing unit 211 in this manner, the radar device 10 can determine the Doppler frequency fd of the target object within the range of -1 / (2Tr)≦fd<1 / (2Tr) and obtain an output in which the transmission antennas are associated with each Doppler multiplexed signal.

[0673] In the above, each embodiment of the present disclosure has been described.

[0674] [Other embodiments]

[0675] In addition, in a radar device of an embodiment of the present disclosure, the radar transmitting unit and the radar receiving unit may also be respectively configured at physically separate locations. In addition, in a radar receiving unit of an embodiment of the present disclosure, the direction estimation unit and other components may also be independently configured at physically separate locations.

[0676] In addition, the number of transmitting antennas Nt, the number of receiving antennas Na, and the number of Doppler multiplexing N used in one embodiment of the present disclosure are DM , the number of beams of multi-beam NB, the number of transmitting antennas in each beam direction N Bq The numerical values ​​of parameters such as the Doppler shift amount and the Doppler shift interval are examples, and the number of parameters is not limited to these values. In addition, a part of the transmission antennas provided in the radar device may be used as the number of transmission antennas Nt.

[0677] In addition, the configuration example (e.g., configuration example A, configuration example B) of the MIMO antenna used in one embodiment of the present disclosure is described as a case where a radar transmission signal is transmitted from a plurality of transmission antennas using Doppler multiplexing transmission, but the present invention is not limited thereto. For example, the present invention can also be applied to a case where a radar transmission signal is transmitted from a plurality of transmission antennas using time division multiplexing transmission or code multiplexing transmission, and the effect brought about by the configuration of the disclosed MIMO antenna can be obtained.

[0678] Although not shown in the figure, the radar device of one embodiment of the present disclosure has, for example, a CPU (Central Processing Unit), a storage medium such as a ROM (Read Only Memory) storing a control program, and a working memory such as a RAM (Random Access Memory). In this case, the functions of the above-mentioned parts are realized by the CPU executing the control program. However, the hardware structure of the radar device is not limited to this example. For example, each functional part of the radar device can also be realized as an integrated circuit, that is, an IC (Integrated Circuit). Each functional part can be independently monolithic or monolithic in a manner that includes part or all of it.

[0679] Various embodiments have been described above with reference to the accompanying drawings, but the present disclosure is of course not limited to these examples. As long as one is skilled in the art, it is obvious that various variations or modifications can be thought of within the scope described in the claims, and it should be understood that these variations or modifications also belong to the technical scope of the present disclosure. In addition, the constituent elements of the above-mentioned embodiments can be arbitrarily combined within the scope of the disclosure purpose.

[0680] In addition, the expression "part" in the above-mentioned embodiments can also be replaced by other expressions such as "...circuitry", "...component (assembly)", "device (device)", "unit (unit)" or "module (module)".

[0681] In the above-mentioned embodiments, an example in which the present disclosure is configured using hardware has been described. However, the present disclosure may also be implemented by software in cooperation with hardware.

[0682] In addition, each functional block used in the description of the above-mentioned embodiments is typically implemented as an integrated circuit, i.e., LSI (Large Scale Integration). The integrated circuit can also control each functional block used in the description of the above-mentioned embodiments, and includes input terminals and output terminals. These functional blocks can be independently monolithic, or can be monolithic in a manner that includes a part or all. It is referred to as "LSI" here, but it can also be referred to as "IC", "system LSI (system LSI)", "super LSI (super LSI)", "ultra-large LSI (ulira LSI)" depending on the degree of integration.

[0683] In addition, the method of integrated circuitization is not limited to LSI, and it can also be realized using a dedicated circuit or a general-purpose processor. It is also possible to use an FPGA (Field Programmable Gate Array) that can be programmed after LSI manufacturing, or a reconfigurable processor that can reconfigure the connection or setting of the circuit blocks inside the LSI.

[0684] Furthermore, if integrated circuit technology that replaces LSI emerges as semiconductor technology advances or other derived technologies emerge, it is of course possible to use this technology to integrate functional blocks. There is also the possibility of applying biotechnology, etc.

[0685] <Summary of the present disclosure>

[0686] A radar device according to an embodiment of the present disclosure includes: a plurality of transmitting antennas, including a first transmitting antenna forming a first beam and a second transmitting antenna forming a second beam different from the first beam; and a transmitting circuit for multiplexing and transmitting, from the plurality of transmitting antennas, transmitting signals to which phase rotations corresponding to Doppler frequency shift amounts respectively allocated to the plurality of transmitting antennas are assigned, wherein a first pattern of Doppler frequency shift amounts allocated to the first transmitting antenna is different from a second pattern of Doppler frequency shift amounts allocated to the second transmitting antenna based on the fact that Doppler frequency shift intervals of the plurality of transmitting antennas are unequally spaced on a Doppler frequency axis.

[0687] In one embodiment of the present disclosure, the first mode and the second mode are related to the Doppler frequency shift interval, the Doppler multiplexing number based on the first transmitting antenna is the same as the Doppler multiplexing number based on the second transmitting antenna, and at least one of the Doppler frequency shift intervals based on the first transmitting antenna is different from the Doppler frequency shift interval based on the second transmitting antenna.

[0688] In one embodiment of the present disclosure, the first mode and the second mode are related to the number of transmitting antennas, and the number of the first transmitting antennas is different from the number of the second transmitting antennas.

[0689] In one embodiment of the present disclosure, the first mode and the second mode are related to a Doppler multiplexing number, and a Doppler multiplexing number based on the first transmitting antenna is different from a Doppler multiplexing number based on the second transmitting antenna.

[0690] In one embodiment of the present disclosure, the first mode and the second mode are related to the order of the intervals of the Doppler frequency shift amounts, the Doppler multiplexing number based on the first transmitting antenna is the same as the Doppler multiplexing number based on the second transmitting antenna, the multiple first Doppler frequency shift intervals based on the first transmitting antenna are the same as the multiple second Doppler frequency shift intervals based on the second transmitting antenna, and the order of the multiple first Doppler frequency shift intervals on the Doppler frequency axis is different from the order of the multiple second Doppler frequency shift intervals on the Doppler frequency axis.

[0691] In one embodiment of the present disclosure, on the Doppler frequency axis, the Doppler frequency shift intervals based on the first transmitting antenna are unequally spaced.

[0692] In one embodiment of the present disclosure, on the Doppler frequency axis, the Doppler frequency shift intervals based on the second transmitting antenna are unequally spaced.

[0693] In one embodiment of the present disclosure, the device further comprises: a plurality of receiving antennas for receiving reflected wave signals generated by the transmission signal reflected from a target; and a receiving circuit for estimating the direction of the target using the reflected wave signals.

[0694] In one embodiment of the present disclosure, there are also multiple receiving antennas arranged at a first interval in a first direction, the first transmitting antenna and the second transmitting antenna are arranged at the first interval in the first direction, and are arranged at different positions in a second direction orthogonal to the first direction.

[0695] In one embodiment of the present disclosure, there are also multiple receiving antennas arranged at a first interval in a first direction, the first transmitting antenna and the second transmitting antenna are arranged at a second interval in the first direction, and the difference between the first interval and the second interval is a specified value based on the wavelength of the transmission signal.

[0696] In one embodiment of the present disclosure, the prescribed value is a value within a range of 0.45 times to 0.8 times the wavelength.

[0697] In one embodiment of the present disclosure, the first transmitting antenna and the second transmitting antenna are configured at the same position in a second direction orthogonal to the first direction.

[0698] In one embodiment of the present disclosure, the first transmitting antenna and the second transmitting antenna are arranged at different positions in a second direction orthogonal to the first direction.

[0699] In one embodiment of the present disclosure, among the multiple receiving antennas, the first receiving antenna and the second receiving antenna are configured at different positions in the second direction.

[0700] In one embodiment of the present disclosure, the number of the first transmitting antenna and the number of the second transmitting antenna are respectively 1, and the number of Doppler frequency shift amounts allocated to the first transmitting antenna is different from the number of Doppler frequency shift amounts allocated to the second transmitting antenna.

[0701] In one embodiment of the present disclosure, in each transmission cycle of the transmission signal, the number of the Doppler frequency shift amounts allocated to the first transmission antenna is swapped with the number of the Doppler frequency shift amounts allocated to the second transmission antenna.

[0702] In one embodiment of the present disclosure, at least one of a beam direction and a beam width of the first beam and the second beam is different.

[0703] The disclosure contents of the specification, drawings and abstract contained in the Japanese patent application No. 2022-138273 filed on August 31, 2022 are all cited in this application.

[0704] Industrial Applicability

[0705] The present disclosure is suitable as a radar device that detects a wide-angle range.

[0706] Description of Reference Numerals

[0707] 10 Radar device

[0708] 100 Radar Transmitter

[0709] 101 Radar signal generation unit

[0710] 102 Modulation signal generation unit

[0711] 103 VCO

[0712] 104 Doppler shift unit

[0713] 105 Transmitting antenna unit

[0714] 200 Radar receiving unit

[0715] 201 Antenna System Processing Department

[0716] 202 Receiving antenna unit

[0717] 203 Receiving wireless unit

[0718] 204 Mixer Department

[0719] 205 LPF

[0720] 206 Signal Processing Department

[0721] 207 AD conversion unit

[0722] 208 Beat Frequency Analysis Department

[0723] 209 Doppler Analysis Department

[0724] 210 CFAR Department

[0725] 211 Doppler multiplexing and demultiplexing unit

[0726] 212 Direction Estimation Unit

Claims

1. A radar device, characterized in that: have: A plurality of transmit antennas, including a first transmit antenna forming a first beam and a second transmit antenna forming a second beam different from the first beam; as well as a transmitting circuit that multiplexes and transmits, from the plurality of transmitting antennas, transmission signals to which phase rotations corresponding to the Doppler shift amounts assigned to the plurality of transmitting antennas are applied, respectively; Based on the fact that the Doppler frequency shift intervals of the plurality of transmitting antennas are unequally spaced on the Doppler frequency axis, A first pattern of Doppler frequency shift amounts assigned to the first transmission antenna is different from a second pattern of Doppler frequency shift amounts assigned to the second transmission antenna.

2. The radar device according to claim 1, wherein: The first mode and the second mode are related to the Doppler frequency shift interval, The Doppler multiplexing number based on the first transmitting antenna is the same as the Doppler multiplexing number based on the second transmitting antenna. At least one of the Doppler shift intervals based on the first transmit antenna is different from the Doppler shift interval based on the second transmit antenna.

3. The radar device according to claim 1, wherein: The first mode and the second mode are related to the number of transmitting antennas. The number of the first transmitting antennas is different from the number of the second transmitting antennas.

4. The radar device according to claim 1, wherein: The first mode and the second mode are related to the Doppler multiplexing number. The Doppler multiplexing number based on the first transmitting antenna is different from the Doppler multiplexing number based on the second transmitting antenna.

5. The radar device according to claim 1, wherein: The first mode and the second mode are related to the order of the intervals of the Doppler frequency shift amounts. The Doppler multiplexing number based on the first transmitting antenna is the same as the Doppler multiplexing number based on the second transmitting antenna. A plurality of first Doppler frequency shift intervals based on the first transmitting antenna are the same as a plurality of second Doppler frequency shift intervals based on the second transmitting antenna, An order of the plurality of first Doppler frequency shift intervals on the Doppler frequency axis is different from an order of the plurality of second Doppler frequency shift intervals on the Doppler frequency axis.

6. The radar device according to claim 1, wherein: On the Doppler frequency axis, the Doppler frequency shift intervals based on the first transmitting antenna are unequally spaced.

7. The radar device according to claim 1, wherein: On the Doppler frequency axis, the Doppler frequency shift intervals based on the second transmitting antenna are unequally spaced.

8. The radar device according to claim 1, wherein: Also available: A plurality of receiving antennas for receiving reflected wave signals generated by the transmitted signal reflected from a target; and The receiving circuit uses the reflected wave signal to estimate the direction of the target.

9. The radar device according to claim 1, wherein: It also includes a plurality of receiving antennas arranged at a first interval in a first direction, The first transmitting antenna and the second transmitting antenna are arranged at the first interval in the first direction, and are arranged at different positions in a second direction orthogonal to the first direction.

10. The radar device according to claim 1, wherein: It also includes a plurality of receiving antennas arranged at a first interval in a first direction, The first transmitting antenna and the second transmitting antenna are arranged at a second interval in the first direction, The difference between the first interval and the second interval is a prescribed value based on the wavelength of the transmission signal.

11. The radar device according to claim 10, wherein: The prescribed value is a value within a range of 0.45 to 0.8 times the wavelength.

12. The radar device according to claim 10, wherein: The first transmitting antenna and the second transmitting antenna are arranged at the same position in a second direction orthogonal to the first direction.

13. The radar device according to claim 10, wherein: The first transmitting antenna and the second transmitting antenna are arranged at different positions in a second direction orthogonal to the first direction.

14. The radar device according to claim 9 or 10, wherein: Among the plurality of receiving antennas, a first receiving antenna and a second receiving antenna are arranged at different positions in the second direction.

15. The radar apparatus according to claim 1, wherein: The number of the first transmitting antenna and the number of the second transmitting antenna are both 1, The number of Doppler frequency shift amounts allocated to the first transmitting antenna is different from the number of Doppler frequency shift amounts allocated to the second transmitting antenna.

16. The radar device according to claim 13, wherein: The number of the Doppler frequency shift amounts allocated to the first transmission antenna and the number of the Doppler frequency shift amounts allocated to the second transmission antenna are exchanged in each transmission cycle of the transmission signal.

17. The radar apparatus according to claim 1, wherein: The first beam and the second beam are different in at least one of a beam direction and a beam width.

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