Tdm fmcw radar device and signal processing method of the device

Abstract

Transmit antennas and receive antennas are arranged such that multiple virtual antennas have the same location in a time division multiplexed (TDM) frequency modulated continuous wave (FMCW) radar device. At least three special chirps are located in consecutive time slots, respectively, and have different periods, at least one of the at least three special chirps being included in each chirp cycle in a waveform signal transmitted by the multiple virtual antennas having the same location. A Doppler frequency can be uniquely determined from phase difference values between the at least three special chirps in consecutive time slots measured in FMCW radar signals received at the multiple virtual antennas, respectively.

Description

Technical Field

[0001] A signal processing technique for time-division-multiplexed (TDM) frequency-modulated continuous wave (FMCW) radar equipment is disclosed. Background Technology

[0002] A multiple-input multiple-output (MIMO) frequency-modulated continuous wave (FMCW) radar device achieves improved angular resolution at low cost using multiple transmit antennas and multiple receive antennas. A time-division multiplexing (TDM) MIMO radar device uses a time-division multiplexing (TDM) scheme to distinguish transmitted waveform signals at the receive antennas.

[0003] Figure 1 An antenna array in an exemplary FMCW radar device is shown, consisting of a TX transmitting antenna and an RX receiving antenna. In the exemplary TDM FMCW radar device, the TX transmitting antenna sequentially transmits FMCW radar waveform signals, and each transmitted FMCW radar waveform signal is reflected by the target and simultaneously received by the RX receiving antenna. The transmitting and receiving antennas are generally arranged linearly with equal spacing, but can also be arranged non-linearly with non-equal spacing. As shown, when the j-th receiving antenna receives the signal transmitted by the i-th transmitting antenna, a signal substantially the same as the signal obtained when the virtual transmitting / receiving antenna is located at position (i, j) can be obtained. The virtual transmitting / receiving antenna is the case where the transmitting and receiving antennas are located at approximately the same position, and is referred to herein as a "virtual antenna".

[0004] Figure 2 This is a schematic diagram illustrating an example of range-Doppler processing used to estimate range and velocity from TDM FMCW radar signals. In a TDM FMCW radar device, a frame consists of N... C Composed of N chirps C Each chirp is generated in a time-division manner from N. TX Each of the transmitting antennas repeatedly transmits N. Loop N times. That is, N C =N TX ×N Loop As shown in the figure, range Doppler processing is performed equally on all virtual antennas. For example, in a configuration with N... TX One transmitting antenna and N RX In a TDMFMCW radar device consisting of an array of receiving antennas, it can detect N... TX ×N RX Each of the virtual antennas performs as follows: Figure 2The distance Doppler processing is shown.

[0005] As shown in the figure, when the transmitting antenna sequentially transmits FMCW radar waveform signals, the receiving antenna RX1, like other receiving antennas, receives all reflected waves from one or more targets. The phase difference between the signal transmitted from the transmitting antenna and the signal received at the receiving antenna depends on the distance from the transmitting antenna to the receiving antenna via the target. The frequency difference between the transmitted and received signals is called the beat frequency, and this beat frequency can be estimated from the peak position (i.e., the FFT index) of the output coefficients of the range Fast Fourier Transform (FFT). Since the beat frequency corresponds one-to-one with the distance to the target, the distance to the target can be estimated by estimating the beat frequency.

[0006] exist Figure 2 In this example, the signal of the virtual antenna at position (0,1), i.e., the signal of the virtual antenna when the first receiving antenna receives the signal transmitted by the 0th transmitting antenna, will be described. First, the distance from the FFT processor 210-1 to 210-N... Loop Perform internal chirping.

[0007] The difference between the transmitted signal transmitted from the transmitting antenna TX0 in the first chirped cycle of the frame and the signal reflected by the target and received by the receiving antenna RX1 is sampled by the distance FFT processor 210-1, transformed to the frequency domain in chirped units, and stored in buffer 230-1 for each coefficient. The difference between the transmitted signal transmitted from the transmitting antenna TX0 in the second chirped cycle of the frame and the signal reflected by the target and received by the receiving antenna RX1 is sampled by the distance FFT processor 210-2, transformed to the frequency domain in chirped units, and stored in buffer 230-2 for each coefficient. The difference between the transmitted signal transmitted from the transmitting antenna TX0 in the last chirped cycle of the frame and the signal reflected by the target and received by the receiving antenna RX1 is sampled by the distance FFT processor 230-N. Loop Sample the data and transform it to the frequency domain in units of chirp, then store each coefficient in a buffer of 2^30-N. Loop The beat frequency can be estimated by finding the peak position in the coefficients stored in the buffer. The peak position is the shaded area in the figure, and the distance to the target can be obtained from this.

[0008] Simultaneously, as the target moves, the distance between the radar equipment and the target changes over time, a phenomenon known as range offset. Range offset causes a phase change in the FMCW radar signal, the extent of which is determined by the target's radial velocity. Therefore, the target's radial velocity can be estimated by observing the phase change over time. As the total observation time of phase changes increases, even very small phase changes can be detected, thus improving radial velocity resolution. On the other hand, as the interval between observations of phase changes decreases, faster changes can be detected, thereby increasing the limit of detectable radial velocities.

[0009] To estimate the target's range and radial velocity based on signals received from a virtual antenna, two-dimensional spectral estimation schemes such as two-dimensional (2D)-FFT or two-dimensional multi-signal classification (MUSIC) are applied to the range-Doppler matrix. The range-angle matrix is ​​obtained from the MIMO antenna array, where the dimension of the angle increases to the same size as the virtual array.

[0010] exist Figure 2 In the example, each of the Doppler FFT processors 250-1 to 250-M performs chirp-inter-processing. Each of the Doppler FFT processors 250-1 to 250-M receives data from the distance FFT processor 210-N. Loop The same number of output coefficients, that is, N corresponding to the same frequency. Loop The output coefficients are processed by an FFT, and the transformed coefficients are stored in a 2D buffer 270. Distance FFT processors 210-1 to 210-N are provided. Loop The number of output coefficients is the same as that of M Doppler FFT processors, i.e., 250-1 to 250-M. Buffer 270 stores the range-Doppler spectrum values ​​obtained by range FFT and Doppler FFT. The Doppler frequency can be determined by identifying the location of peaks in the Doppler FFT output spectrum stored in buffer 270, such as the shaded area in the figure, and the radial velocity of the target can be obtained from the Doppler frequency.

[0011] Doppler FFT is applied to signals acquired from the same TX-RX channel or virtual antenna. Because the physical locations of the transmit and receive antennas corresponding to the channels, and the angle of the target, signals received from different channels have different initial phases. Therefore, a TDM FMCW system should always use only signals obtained from the same channel as its Doppler FFT input in order to observe only the phase change over time.

[0012] In a TDM FMCW system, when the length of a chirp is denoted as T chirpAt that time, the time difference between the input samples of the Doppler FFT becomes T. loop =T chirp ×N TX Because radio waves originate from N TX The transmission antennas transmit sequentially. In this case, the rate of change of distance caused by the target's movement, i.e., the radial velocity, is expressed as v. r At that time, the Doppler frequency is given as f d =2v r / λ. Here, λ refers to the length of a wavelength. In this case, when the phase difference between the input samples of the Doppler FFT is expressed as Δf, the relationship Δf=2πf d T loop Established.

[0013] To estimate the spectrum without aliasing, according to Nyquist sampling theory, at least two samples should be taken within one period. This means the phase difference between samples should be within ±π. In other words, to properly estimate the radial velocity of the target, the following condition must be met:

[0014] Equation 1

[0015] |2πf d T loop |<π.

[0016] Because of T loop Always positive, using the relation f d =2v r / λ, Equation (1) can be expressed as:

[0017] Equation 2

[0018]

[0019] That is, in TDM FMCW, as the number of transmit antennas increases, T loop As the number of transmitting antennas increases, the maximum measurable radial velocity under aliasing-free conditions decreases proportionally to the number of transmitting antennas. For example, in a 77 GHz radar system with 12 transmitting antennas and a chirp length of 40 ms, the maximum measurable radial velocity is only about + / - 7.3 km / h.

[0020] Figure 3 The figure illustrates the velocity spectrum that can be estimated from the Doppler FFT output spectrum. As shown, the velocity spectrum estimated from the Doppler FFT output spectrum includes both the observable spectrum and the aliasing spectrum. The resulting velocity may include both the true velocity and the measured velocity, thus introducing the Doppler ambiguity problem. Therefore, as... Figure 3 As shown, when the target moves beyond the specified distance... Figure 3In the example where the maximum measurable radial velocity is limited, the radial velocity of the target becomes difficult to estimate accurately due to aliasing. Since the incorrect estimation of the target's radial velocity has a decisive impact on the error in estimating the target angle, this Doppler ambiguity problem must be addressed.

[0021] Methods to address this problem have been disclosed in related technologies (Roos, Fabian et al., “Enhancement of Doppler unambiguity for chirp-sequence modulated TDM MIMO radars,” disclosed at the IEEE International Conference on Intelligent Mobile Microwave (ICMIM) 2018, IEEE, 2018; or Schmid, Christian M. et al., “Motion compensation and efficient array design for TDMA FMCW MIMO radar systems,” disclosed at the 6th European Conference on Antennas and Propagation (EUCAP) 2012, IEEE, 2012). These papers propose an antenna arrangement with a specific structure to separate the phase rotation caused by the Doppler effect from the phase rotation component determined by the target position and the virtual antenna positions. These methods primarily estimate the radial velocity of the target in the range-Doppler spectrum and then use information about the phase changes between the virtual antennas to estimate the radial velocity of the target again. However, this method requires the antenna to be designed as a spatially long, uniform virtual array, where the transmitting or receiving antennas are arranged at equal intervals of 0.5 wavelengths. Otherwise, the antenna must be designed with a large number of virtual array elements overlapping in space. That is, due to the extremely limited freedom in antenna design, related technologies are difficult to apply to sparse arrays, leading to problems such as antenna coupling and reduced angular resolution. Furthermore, even if the antenna is designed to meet the above design conditions, the minimum time interval for measuring phase rotation is T. chirp The maximum estimable radial velocity will not exceed the physical limit of Equation 2.

[0022] Another related technical paper (Wojtkiewicz, Andrzej et al., “Two-dimensional signal processing in FMCW radars”, disclosed in Proc. XXKKTOiUE (1997):475-480) discloses a method for processing two or more different T... chirpThis method uses a concatenation of subframes. Here, a frame consists of several subframes. Structurally, a subframe is identical to a frame in a conventional TDM FMCW signal. However, due to the use of two or more subframes in this method, there are drawbacks such as excessively long frame lengths and high data throughput. Furthermore, it is difficult to maximize signal processing gain because the large start time difference between subframes reduces signal coherence, and it is difficult to correctly correlate the detected target in each subframe when the target's range changes significantly due to distance offsets between subframes.

[0023] To address the range offset and coherence issues in the aforementioned papers, another related paper (Kronauge, Matthias, and Hermann Rohling, “New chirp sequence radar waveform,” disclosed in IEEE Transactions on Aerospace and Electronic Systems 50.4 (2014):2870-2877) proposed a method of interleaving on the time axis by adding frequency offsets between subframes. However, this method is also difficult to use in practice because the frame length becomes too long in the aforementioned related techniques, and even then, the method may only be used in a limited way at very low sampling rates. Summary of the Invention

[0024] The summary of this invention introduces a series of concepts in a simplified form, which are further described in the detailed description section below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to help determine the scope of the claimed subject matter.

[0025] The following description relates to a method for increasing the detectable radial velocity limit of a target at a given number of transmit antennas in a time-division multiplexing (TDM) frequency-modulated continuous wave (FMCW) radar device.

[0026] The following description also relates to increasing the detectable radial velocity of a target without increasing the frame length in a TDM FMCW radar device.

[0027] The following description also addresses the problem of Doppler ambiguity in TDM FMCW radar equipment.

[0028] The following description also addresses the solution to the Doppler ambiguity problem while minimizing the increase in frame length in TDM FMCW radar equipment.

[0029] The following description also addresses resolving the Doppler ambiguity problem while minimizing additional constraints in the antenna design of TDM FMCW radar equipment.

[0030] According to one aspect of the invention, the transmitting antenna and the receiving antenna are arranged such that a plurality of dummy antennas have the same location in the TDMFMCW radar device. At least three specific chirps are located in consecutive time slots and have different periods, and at least one of the at least three specific chirps is included in each chirp cycle of the waveform signal transmitted by the plurality of dummy antennas having the same location. The Doppler frequency can be determined by the phase difference between the at least three specific chirps located in consecutive time slots, which are measured in FMCW radar signals received from the plurality of dummy antennas.

[0031] According to another aspect, at least three special chirps, which are located in consecutive time slots and have different periods, are configured to differ in at least one aspect, either the idle time between special chirps or the ramp time of a special chirp.

[0032] According to another aspect, at least three chirps located in consecutive time slots are configured such that the sum of the specific chirp difference during idle time and the specific chirp difference during ramp time is limited by the target's maximum target detection rate.

[0033] According to another aspect, the true value of the Doppler frequency can be determined based on the phase difference between specific chirps measured from at least three specific chirp signals having a period different from the measured value. Specifically, the Doppler frequency of the aliasing spectrum whose theoretically calculated phase difference has the most similar value to the measured phase difference can be determined as the true Doppler frequency.

[0034] In another respect, the search distance for the Doppler frequencies of the aliased spectrum can be determined by the ratio of the maximum Doppler frequency of the target to be detected to the maximum Doppler frequency obtained from the distance Doppler spectrum. Attached Figure Description

[0035] Figure 1 An antenna array in an exemplary frequency modulated continuous wave (FMCW) radar device is shown, which consists of a TX transmitting antenna and an RX receiving antenna.

[0036] Figure 2 This is a diagram illustrating an example of range Doppler processing used to estimate range and radial velocity from time-division multiplexing (TDM) FMCW radar signals.

[0037] Figure 3 The velocity spectrum that can be estimated from the output spectrum of the Doppler Fast Fourier Transform (FFT) is shown.

[0038] Figure 4 This is a flowchart illustrating the configuration of a signal processing method for a TDM FMCW radar device according to an embodiment.

[0039] Figure 5This is a flowchart illustrating the configuration of a spectrum analysis operation according to an embodiment.

[0040] Figure 6 A typical frame structure of radar waveforms in a TDM FMCW radar device according to an embodiment is shown.

[0041] Figure 7 An example of an antenna array to which the present invention can be applied is shown.

[0042] Figure 8 An example of a special chirp in a waveform signal transmitted by a virtual antenna, located in consecutive time slots, is shown.

[0043] Figure 9 Another example is shown of a special chirp in which a waveform signal transmitted by a virtual antenna is located in consecutive time slots.

[0044] Figure 10 The process of obtaining the range-Doppler spectrum by performing range-Doppler processing in a typical TDM FMCW radar device is shown.

[0045] Figure 11 This is a flowchart illustrating the configuration of the Doppler frequency determination operation according to an embodiment.

[0046] Figure 12 This is a block diagram illustrating the structure of a TDM FMCW radar device according to an embodiment.

[0047] Figure 13 This is a configuration block diagram of a spectrum analyzer according to an embodiment.

[0048] Figure 14 This is a block diagram illustrating the configuration of a Doppler frequency determiner according to an embodiment. Detailed Implementation

[0049] The foregoing and additional aspects of the present invention will be embodied by the following embodiments described with reference to the accompanying drawings. It should be understood that various combinations of components in each embodiment are possible unless otherwise stated or contradicted in the embodiments. It should be understood that words or terms used in the specification and claims should be interpreted as having the meaning consistent with their meaning in the context of the specification and the technical concept of the invention, based on the inventor's ability to correctly define the meaning of words or terms to best interpret the principles of the invention. In the following, exemplary embodiments of the invention will be described in detail with reference to the accompanying drawings.

[0050] According to one aspect, the transmitting and receiving antennas are arranged such that multiple dummy antennas have the same location in a time-division multiplexing (TDM) frequency-modulated continuous wave (FMCW) radar device. At least three specific chirps are located in consecutive time slots and have different periods, and at least one of the at least three specific chirps is included in each chirp loop of the waveform signal transmitted by the multiple dummy antennas with the same location. The Doppler frequency can be determined by the phase difference between the at least three specific chirps located in consecutive time slots, which are measured in the FMCW radar signal received from the multiple dummy antennas.

[0051] Figure 4 This is a flowchart illustrating the configuration of a signal processing method for a TDM FMCW radar device according to an embodiment. As shown, the signal processing method for the TDM FMCW radar device according to an embodiment includes a wireless transmission operation 410, a wireless reception operation 420, a spectrum analysis operation 430, and a Doppler frequency determination operation 440.

[0052] This invention describes N TX One transmitting antenna and N RX This is the case of a TDM FMCW radar device consisting of an array of receiving antennas. In this radar device, a radio transmission operation 410 is performed at each transmitting antenna, a radio reception operation 420 is performed at each receiving antenna, and a spectrum analysis operation 430 and a Doppler frequency determination operation 440 can be performed at all virtual antennas.

[0053] According to one aspect, the transmitting and receiving antennas are arranged such that the plurality of dummy antennas have the same position. In radio transmission operation 410, the radar device transmits an FMCW radar waveform signal via the transmitting antenna array. According to one aspect, at least three specific chirps are configured to be located in consecutive time slots and have different periods, and at least one of the at least three specific chirps is included in the chirp cycle of each FMCW radar waveform signal transmitted by the plurality of dummy antennas arranged in the same position. Here, the expression that the three chirps located in consecutive time slots have different periods includes the case that two of the three chirps have the same period and the remaining one has a different value, or the case that all three have different values.

[0054] Figure 6 A typical frame structure of a radar waveform in a TDM FMCW radar device according to an embodiment is shown. A frame is a unit of spectral analysis, and the number of chirped cycles contained in a frame is denoted here as N. Loop . Figure 6 Only two chirp cycles as part of a single frame are illustrated. In the diagram, T loopThis is the length of the chirp cycle. The length of the chirp cycle is the period required for all transmitting antennas to transmit a signal once. Each frame consists of one or more chirp cycles, and each chirp cycle consists of one or more chirps. Here, the number of chirps in each chirp cycle is represented by N. TX The number of chirps in each chirp cycle is usually equal to the number of transmit antennas. When the position index of a chirp in a chirp cycle is represented as p, the value of p is 0 <= p <= N. TX Within the range of -1.

[0055] Figure 6 The upper right corner of the diagram illustrates the waveform of a single chirped cycle of the radar waveform signal. Here, α represents the sweep rate.

[0056] T idle,p The idle time of the p-th chirp;

[0057] T ramp,p : The length of the frequency variation of the p-th chirp;

[0058] T chirp,p The chirping period of the p-th chirp (=T) idle,p +T ramp,p );

[0059] T ADC Sampling delay is the time difference between the start of chirping and the start of sampling.

[0060] f0: Chirp start frequency.

[0061] In this invention, the sweep frequency α, the chirp initiation frequency f0, and the sampling delay T are... ADC It is assumed that the delay component is the same for all chirs. The delay component between the transmit antenna TX(p) and the receive antenna q used to transmit the p-th chirp is denoted as τ. TX(0),q At that time, τ TX(0),q The value is determined by the target's azimuth and elevation angles, the relative position of the virtual antenna specified by TX(p), and the antenna reference point q in space.

[0062] Figure 7An example of an antenna array to which the present invention can be applied is shown. The Virtual Antenna Array is shown when three (TX) transmit antennas and four (RX) receive antennas are arranged as shown. Each circle represents the position of a virtual antenna, and the two numbers represent the transmit antenna index and the receive antenna index, respectively. The three virtual antennas generated by transmit antenna TX1 and receive antenna RX4, transmit antenna TX2 and receive antenna RX3, and transmit antenna TX3 and receive antenna RX1 are all generated in the same virtual antenna position P. The present invention can be applied to TDM FMCW radar equipment having transmit and receive antennas arranged such that multiple virtual antennas have the same position. According to one aspect, at least three specific chirps are located in consecutive time slots and have different periods, and at least one of the at least three specific chirps is included in each chirp cycle of the waveform signal transmitted by the multiple virtual antennas having the same position. Here, a time slot refers to a time slot on the time axis, distinguished by a chirp count that increases sequentially in the chirp cycle. Furthermore, the expression that chirps are located in consecutive time slots means that the chirp count in the chirp cycle to which a particular chirp belongs is a sequentially increasing value, rather than meaning that the chirps are adjacent to the same chirp cycle or that the chirps are emitted sequentially.

[0063] In the case of MIMO radar equipment, typically, the transmitting antenna transmits signals sequentially, and the receiving antenna receives signals simultaneously. Therefore, in Figure 7 In the example, even when the FMCW radar waveform signal is received at the virtual antenna, the time difference sequence is transmit antenna TX1 and receive antenna RX4, transmit antenna TX2 and receive antenna RX3, and transmit antenna TX3 and receive antenna RX1. The FMCW radar waveform signal is buffered in memory so that all the special chirps located in consecutive time slots can become available when the signal is processed according to the invention.

[0064] According to one aspect, with Figure 6 Unlike the general waveform signal shown, each chirp cycle of the FMCW radar waveform signal transmitted by the radar device applying the signal processing method according to the embodiment may include at least N. TX +1 chirp. As an example, N TX The chirp is an effective chirp used to estimate the beat frequency and Doppler frequency, and can be derived from the Nth chirp. TX At least two consecutive chirps in a chirp cycle acquire information to determine the Doppler frequency. However, the invention is not limited thereto; consecutive specific chirps in a chirp cycle may be located at the beginning or middle of the chirp cycle.

[0065] Figure 8An example of special chirps located in consecutive time slots for waveform signals transmitted by a virtual antenna is shown. Special chirps with a chirp count of 3 in virtual antenna VA1, special chirps with a chirp count of 4 in virtual antenna VA2, and special chirps with a chirp count of 5 in virtual antenna VA3 are moved to the virtual time slot VTS. These special chirps have chirp counts in each chirp cycle of the radar waveform signal, but when these special chirps are clustered on the same virtual time slot axis, they have sequentially increasing count values. In this sense, it is stated here that the special chirps are located in “consecutive time slots”.

[0066] Figure 9 Another example is shown of special chirps located in consecutive time slots for waveform signals transmitted by virtual antennas. The special chirp with a chirp count of 3 in virtual antenna VA1 and the special chirps with chirp counts of 4 and 5 in virtual antenna VA2 are moved to the virtual time slot VTS. The special chirp of "3" and the special chirps of "4 and 5" have chirp counts in each chirp cycle of the radar waveform signal, but when these chirps are clustered on the same virtual time slot axis, they have sequentially increasing count values. In this sense, it is stated here that the special chirps are located in "consecutive time slots".

[0067] In the radio receiving operation 420, the radar equipment uses a receiving antenna to receive the FMCW radar waveform signal reflected by the target, demodulates the baseband FMCW radar signal, samples the difference signal between the baseband FMCW radar signal and the transmitted signal, and converts the sampled signal into a digital signal and outputs it.

[0068] In spectrum analysis operation 430, the radar device determines and outputs the beat frequency and Doppler frequency from the signal output in radio reception operation 420. In one chirped cycle, N TX Each transmitting antenna sequentially transmits an FMCW radar waveform signal. Each transmitted FMCW radar waveform signal is reflected by the target and then... RX Each receiving antenna receives the signal. In spectrum analysis operation 430, the radar equipment's signal processing circuitry processes the radar waveform signal for each receiving antenna. Furthermore, the radar equipment's signal processing circuitry processes the waveform signal in units of chirp within the same time slot within the loop received by each receiving antenna.

[0069] In the Doppler frequency determination operation 440, the signal processing circuitry of the radar equipment measures the phase difference between at least three specific chirps, located in consecutive time slots and having different periods, received at multiple virtual antennas, and determines and outputs the true Doppler frequency based on the measured values ​​and the Doppler frequency output in the spectrum analysis operation. This will be described in detail below.

[0070] According to an additional aspect of the invention, at least three special chirps, each located in a consecutive time slot and having different periods, are configured to differ in at least one aspect: the idle time between the special chirps or the ramp time of the special chirps. Therefore, due to the Doppler frequency f, signals received from a virtual antenna at the same location can be observed at different time intervals. d The resulting phase components allow us to obtain more information. (Reference) Figure 6 The exemplary waveform within the dashed circle represents the idle time between chirps corresponding to T. idle The ramp time of the chirping corresponds to T. ramp In the example shown, the period of the chirp can be represented as T. chirp =T idle +T ramp .

[0071] According to the present invention, among the three special chirps present in the virtual antenna, based on the reception time, the first special chirp can be configured to differ in terms of ramp time, the last (third) special chirp can be configured to differ in terms of idle time, and the middle (second) special chirp can be configured to differ in both ramp time and idle time. When employing three or more consecutive special chirps, the intermediate chirps in time can all be configured to differ in both ramp time and idle time.

[0072] Similarly, in the illustrated embodiment, the location of a specific chirp with different idle or ramp times in the FMCW radar waveform signal, i.e., its position on the common time slot axis, can be the beginning, middle, or end of each chirp cycle, and the location or content may differ for each wireless transmitter. Figure 8 In the example shown in Or 9, the special chirp is located in the middle of the common time slot axis VTS. As described below, by changing the idle time T between the special chirps... idle and the ramp time T with special chirping ramp Any one of them can provide additional information that enables the determination of the true Doppler frequency from the multiple Doppler frequencies generated by aliasing.

[0073] Figure 5 This is a flowchart illustrating the configuration of a spectrum analysis operation according to an embodiment. As shown, in one embodiment, the spectrum analysis operation may include a distance FFT processing operation 431, a Doppler Fast Fourier Transform (FFT) processing operation 433, a distance estimation operation 435, and a Doppler estimation operation 437.

[0074] In range FFT processing operation 431, the signal processing circuitry of the radar device transforms the digital signal output in radio reception operation 420 into a frequency domain signal in chirp units and outputs it. Although the FFT transform is chosen as an example in the illustrated embodiment, it will be understood that the proposed invention includes various known transforms for frequency domain transformation.

[0075] In Doppler FFT processing operation 433, the radar device's signal processing circuit transforms the same frequency components of the frequency domain signal output in range FFT processing operation 431 back into frequency domain signals and outputs them. In Doppler FFT processing operation 433, after collecting FFT coefficients by frequency (i.e., by FFT index), the radar device's signal processing circuit performs chirp-interval processing by executing FFT. The transformed FFT coefficients are stored in memory. The values ​​stored in memory are range-Doppler spectrum values ​​obtained through range FFT and Doppler FFT.

[0076] In range estimation operation 435, the signal processing circuit of the radar device determines and outputs the beat frequency from the signal output in range FFT processing operation 431. In range estimation operation 435, the signal processing circuit of the radar device can search for the position of the peak in the spectrum output in range FFT processing operation 431, i.e., store the index of the maximum value, to identify the beat frequency and use the beat frequency to calculate the distance to the target.

[0077] In Doppler estimation operation 437, the radar device's signal processing circuitry determines and outputs the Doppler frequency based on the signal output and stored in Doppler FFT processing operation 433. In Doppler estimation operation 437, the radar device's signal processing circuitry can determine the Doppler frequency by identifying the positions of arrays storing peaks in the Doppler spectrum.

[0078] According to another aspect, the true value of the Doppler frequency can be determined based on the phase difference between specific chirps measured from at least three specific chirps located in consecutive time slots and having periods different from the measured values. Specifically, the true Doppler frequency can be determined by the Doppler frequency of the aliasing spectrum whose theoretically calculated phase difference has the most similar value to the measured phase difference.

[0079] Due to the aliasing spectrum, the true Doppler frequency is separated from the measured Doppler frequency by an integer multiple of the aliasing spectrum width. The phase difference of at least three specific chirped signals with different periods, located in consecutive time slots, is calculated based on the Doppler frequencies of the possible candidate aliasing spectra. The Doppler frequency whose phase difference most closely resembles the actual measured phase difference can be estimated as the true Doppler frequency.

[0080] Figure 10The process of obtaining the range-Doppler spectrum by performing range-Doppler processing in a typical TDM FMCW radar device is illustrated. Even in this invention, the range-Doppler processing is similar to... Figure 2 The procedure is as shown, and described using the q-th receiving antenna as an example. When performing the procedure as shown for all TX(p) on each receiving channel... Figure 2 During the signal processing shown, the following can be obtained: Figure 10 The total N shown TX Distance-Doppler spectrum. For example... Figure 10 As shown in gray, in the range-Doppler spectrum, there is a peak in the arrangement of the target's range and radial velocity, and at the peak in the range-Doppler spectrum obtained through TX(p), there exists a phase value →q link, that is, the virtual antenna where the signal transmitted from the p-th transmitting antenna is received by the q-th receiving antenna. Ignoring noise, it is represented as follows.

[0081] Equation 3

[0082]

[0083] α: Sweep frequency;

[0084] α: Sweep frequency;

[0085] T idle,p The idle time of the p-th chirp;

[0086] T ramp,p : The length of the frequency variation of the p-th chirp;

[0087] T chirp,p The chirping period of the p-th chirp (=T) idle,p +T ramp,p );

[0088] T ADC Sampling delay is the time difference between the start of chirping and the start of sampling.

[0089] f0: Chirp start frequency.

[0090] Here, when all virtual antennas' α, f0, and T ADC At the same time, for signals p, p+1, and p+2 received in three consecutive chirps, the relation τ satisfies TX(p),q =τ TX(p+1),q =τ TX(p+2),q ,

[0091] (where τ TX(p),q (This represents the delay component between the transmitting antenna TX(p) and the q-th receiving antenna used to transmit the p-th chirp)

[0092] The phase difference between consecutive chirps can be expressed as follows:

[0093] Equation 4

[0094]

[0095]

[0096]

[0097] The above scenario refers to the case where all chirps are received at a single virtual antenna that has received radar waveform signals transmitted from the same transmitting antenna. In another scenario, the phase difference can be equivalently represented by [Equation 4] even if three chirps included in chirps transmitted by multiple virtual antennas at the same location and located in consecutive time slots satisfy the following conditional expression.

[0098] τ TX(p),q0 =τ TX(p+1),q1 =τ TX(p+2),q2

[0099] Here, the p-th, (p+1)-th, and (p+2)-th chirps transmitted from different transmit antennas TX0, TX1, and TX2 are received at different receive antennas q0, q1, and q2, respectively. In this case, the virtual antennas generated by transmit antenna TX0 and receive antenna q0, the virtual antennas generated by transmit antenna TX1 and receive antenna q1, and the virtual antennas generated by transmit antenna TX2 and receive antenna q2 are presented by overlapping at the same location.

[0100] As another example, the phase difference can be equivalently represented by [Equation 4] even when the following conditional expression is satisfied.

[0101] τ TX(p),q0 =τ TX(p+1),q1 =τ TX(p+2),q1

[0102] Here, the p-th chirp transmitted from different transmit antennas TX0 is received at receive antenna q0, and the (p+1)-th and (p+2)-th chirps transmitted from transmit antenna TX1 are received at another receive antenna q1. In this case, the virtual antennas generated by transmit antenna TX0 and receive antenna q0, as well as the virtual antennas generated by transmit antenna TX1 and receive antenna q1, are presented by overlapping at the same location.

[0103] In summary, it can be seen that in an antenna array in which the transmitting and receiving antennas are arranged such that multiple virtual antennas have the same position, when at least three consecutive special chirps—at least one of which is included in the chirp cycle of each radar signal transmitted by the multiple virtual antennas—are located in consecutive time slots, the phase difference between at least three consecutive special chirps can be represented by [Equation 4].

[0104] As can be seen from Equation 4, the phase difference between chirps located in consecutive time slots is determined by the idle time T. idle and ramp time T ramp Determined. When all chirps have the same idle and ramp times as in a conventional TDM FMCW system, the information obtainable from the phase difference between chirps is limited to 2πf. d (T ramp +T idle ).

[0105] like Figure 10 As shown, in the Doppler processing of the receiving channel of each virtual antenna, the input is the signal received from the same transmitting antenna, and the time difference between the input samples is T. loop When the Doppler frequency caused by the target's movement is expressed as f... d At that time, the smallest phase difference that can be observed by performing Doppler processing is 2πf. d T loop .

[0106] At this point, the maximum Doppler frequency that can be measured by Equation 1 can be expressed as f d,max =1 / (2T) loop ), in f d >|f d,max In the case of |, the radial velocity estimate will have an error because, as Figure 3 The aliasing phenomenon is shown. When the Doppler frequency estimated on the distance-Doppler spectrum is expressed as f... d,measured The actual Doppler frequency is expressed as f. d,true ,f d,true and f d,measured The following relationship exists:

[0107] Equation 5

[0108] f d，true =f d，measured +2kf d，max .

[0109] In Equation 5, k is an arbitrary integer, and k is estimated to determine the actual Doppler frequency f. d,true .

[0110] Figure 11This is a flowchart illustrating the configuration of a Doppler frequency determination operation according to an embodiment. As shown, the Doppler frequency determination operation according to an embodiment may include a phase difference measurement operation 441, a search distance calculation operation 443, and Doppler frequency search operations 445, 447, and 449 with maximum similarity.

[0111] In phase difference measurement operation 441, the signal processing circuit of the radar device measures the phase difference between at least three chirped signals located in consecutive time slots and having different periods. These chirped signals can be signals extracted from chirped cycles received from different virtual antennas, or signals extracted from chirped cycles received from the same virtual antenna. These phase difference values ​​can be measured by detecting the start and end points of each chirp and measuring the time difference between the ends of consecutive chirs. Using the phase difference between chirs obtained from Equation 4, a measurement vector as shown below can be generated from the measured phase difference.

[0112] Equation 6

[0113]

[0114] In the search range calculation operation 443, the signal processing circuit of the radar device determines the search range of the Doppler frequency of the aliased spectrum by the ratio of the maximum Doppler frequency of the target to the maximum Doppler frequency obtained from the range Doppler spectrum.

[0115] In Equation 5, the value of k can be referred to as an index of the Doppler frequencies present in the aliasing spectrum. Aliasing spectra are countless; therefore, appropriately limiting their range is important for the feasibility of the inventions proposed for practical applications.

[0116] When the starting frequency of the FMCW waveform is defined as f0, the maximum moving speed of the target is defined as v. r,max,target At that time, the target's maximum Doppler frequency can be expressed as:

[0117] Equation 7

[0118] (Where, c is the wave speed).

[0119] As can be seen from Equation 4, the minimum measurable time difference is ΔT. ramp +ΔT idle Therefore, when ΔT is substituted into the conditional expression of Equation 1... ramp +ΔT idle Instead of T loop And substitute equation 7 into equation 1 for f d Then, upon rearranging, the following relational expression can be derived.

[0120] Equation 8

[0121]

[0122] As shown in Equation 8, in this invention, at least three chirps located in consecutive time slots are configured such that ΔT ramp and ΔT idle The sum of these two values, namely the chirp difference during idle time and the chirp difference during ramp time, is limited by the target's maximum detection rate. Therefore, using the maximum detection rate determined by the system design requirements, ΔT is appropriately adjusted. ramp and ΔT idle One or both of them satisfy the relationship in Equation 8.

[0123] like Figure 3 As shown in Equation 5, the peak caused by aliasing occurs at a frequency of 2f in the Doppler spectrum. d,max The intervals appear. Therefore, it is greater than or equal to equations 7 and 2f. d,max The ratio, but the smallest integer is determined to be the maximum value of k:

[0124] Equation 9

[0125]

[0126] Among them, 2f d,max,target The maximum Doppler frequency to be detected is 2f. d,max This refers to the maximum Doppler frequency that can be measured through Doppler processing, specifically Doppler FFT. In other words, it's the frequency measured from 2f... d,measured The Doppler frequency (measured primarily through Doppler processing) will reduce k from -k MAX Change to 2f d,max,target k within the range MAX At that time, identify the cause Re{w(k)}. H Maximize k for x}.

[0127] In the Doppler frequency search operations 445, 447, and 449, which have the greatest similarity, the radar equipment's signal processing circuitry determines and outputs the Doppler frequency from the Doppler frequency of the aliased spectrum, at which the theoretically calculated phase difference is most similar to the measured phase difference.

[0128] First, at the target Doppler frequency, the phase difference between at least three chirped signals located in consecutive time slots and having different periods, included in the chirped cycle, is theoretically calculated, and a similarity value (operation 445) is calculated between the theoretically calculated value and the measured value measured in phase difference measurement operation 441. For all Doppler frequencies included in the aliasing spectrum within the search distance, the Doppler frequency with the maximum value among the calculated similarity values ​​is retrieved (447), and the retrieved Doppler frequency is output as the true Doppler frequency (449).

[0129] To compare the measured values ​​with the theoretical calculations, the theoretical values ​​are defined as follows using equations 4 and 5:

[0130] Equation 10

[0131]

[0132] Since the solution k with the highest similarity between the theoretical value of Equation 10 and the measured value of Equation 6 is found, the k that maximizes Re{w(k)Hx} is identified by varying k within an appropriate range, and the actual Doppler frequency is calculated by substituting the estimate into Equation 5. Here, H is the Hermitian operator. Subsequently, based on the Doppler frequency, the relation v is used... r,true =λf d,true / 2 Calculate the radial velocity of the target.

[0133] Figure 12 This is a block diagram illustrating the structure of a TDM FMCW radar device according to an embodiment. As shown, the TDM FMCW radar device according to an embodiment includes a wireless transmitter 410, a wireless receiver 630, a spectrum analyzer 650, and a Doppler frequency determiner 670. In the illustrated embodiment, N is included. TX One wireless transmitter, N RX One wireless receiver and N TX *N RX One spectrum analyzer. That is, since a spectrum analyzer must be provided for each virtual antenna, the NTX spectrum analyzer is connected to each wireless receiver. However, for simplicity, only one wireless transmitter 610, one wireless receiver 630, two spectrum analyzers 650-1 and 650-2, and two Doppler frequency determiners 670-1 and 670-2 are specified in the attached figures.

[0134] According to one aspect, the transmitting antenna and the receiving antenna are arranged such that the plurality of dummy antennas have the same position. The wireless transmitter 610 transmits an FMCW radar waveform signal through the transmitting antenna. According to one aspect, in the FMCW radar waveform signal transmitted by the wireless transmitter 610 using the transmitting antenna constituting the plurality of dummy antennas with the same position, each chirp cycle has at least one special chirp, and there are at least three special chirs. These special chirs are respectively located in consecutive time slots on a common time slot axis, and the at least three special chirs have different periods. Here, the expression that the three special chirs respectively located in consecutive time slots have different periods includes the case where two of the three chirs have the same period and the remaining one has a different value, or the case where all three have different values.

[0135] The wireless receiver 630 uses a receiving antenna to receive the FMCW radar waveform signal reflected from the target, demodulates the baseband FMCW radar signal, samples the difference between the baseband FMCW radar signal and the transmitted signal, and converts the sampled signal into a digital signal for output. The transmitting and receiving antennas are generally arranged linearly with equal spacing, but can also be arranged non-linearly with non-equal spacing.

[0136] The spectrum analyzer 650 determines and outputs the beat frequency and Doppler frequency based on the signal output from the wireless receiver 630. In one chirp cycle, N TX Each transmitting antenna sequentially transmits an FMCW radar waveform signal. Each transmitted FMCW radar waveform signal is reflected by the target and then... RX Each wireless receiver 630 receives a chirp. Each spectrum analyzer 650 processes the chirps output from the wireless receiver 630 corresponding to the period assigned to it by the wireless transmitter 610. For example, spectrum analyzer 650-1 can be assigned to process N chirps that repeat cyclically for each chirp. TX The first chirp of each chirp, and the spectrum analyzer 650-2 can be assigned to process N repeating for each chirp cycle. TX The second chirp of the first chirp.

[0137] The Doppler frequency determiner 670 measures the phase difference between at least three chirps located in consecutive time slots and having different periods, received from the wireless receiver 630, and determines and outputs the true Doppler frequency value based on the measurements taken during spectrum analysis and the Doppler frequency output. This will be described in detail below.

[0138] In another aspect of the invention, at least three chimes located in consecutive time slots are configured to differ in at least one aspect: the idle time between chimes or the ramp time of the chimes. Therefore, it is possible to observe the effect of the Doppler frequency f at different time intervals. d The generated phase components are used to obtain more information. (Reference) Figure 6 The exemplary waveform within the dashed circle represents the idle time between chirps corresponding to T. idle The ramp time of the chirping corresponds to T. ramp In the example shown, the period of the chirp can be represented as T. chirp =T idle +T ramp .

[0139] According to the present invention, in at least three chirs located in consecutive time slots and having different periods, the first chirp can be configured to differ in ramp time, the last chirp can be configured to differ in idle time, and the intermediate chirps can be configured to differ in both ramp time and idle time. In the case of employing three or more chirs located in consecutive time slots and having different periods, the intermediate chirps can be configured to differ in both ramp time and idle time.

[0140] Similarly, in the illustrated embodiment, the chirp positions with different idle or ramp times in the FMCW radar waveform signal can be at the beginning, middle, or end of a cycle, and the position or content may differ for each wireless transmitter. As described below, by changing the idle time T between chirps... idle The ramp time T of chirping ramp This allows us to obtain additional information that enables us to determine the true Doppler frequency from multiple Doppler frequencies generated by aliasing.

[0141] Figure 13 This is a configuration block diagram of a spectrum analyzer according to an embodiment. As shown, in one embodiment, the spectrum analyzer 650 includes a distance FFT processor 651, a distance estimator 652, a Doppler FFT processor 655, and a Doppler estimator 654.

[0142] The distance FFT processor 651 transforms the digital signal output from the wireless receiver 630 into a frequency domain signal in chirps and outputs it. Although the FFT transform is chosen as an example in the illustrated embodiment, it is understood that the proposed invention includes various known transforms for frequency domain transformation. The distance FFT processor 651 performs an FFT transform on the beat frequency signal of the chirps transmitted by its assigned antenna in the chirps present in the first chirp cycle of the digital signal output by the wireless receiver 630 connected to it, and stores the transformed signal in the distance FFT buffer 653. In the next chirp cycle, it performs an FFT transform on the beat frequency signal of the chirps transmitted by the same antenna and stores the transformed signal in the distance FFT buffer 653. Therefore, in the illustrated embodiment, the distance FFT processor 651 processes the FFT transform as many times as the number of chirp cycles, i.e., N. Loop Furthermore, the size of the FFT buffer 653 can store at least N times. Loop A set of FFT coefficients.

[0143] Despite Figure 2 The existence of N is shown in the figure. Loop An example of FFT processor 210, but Figure 10The illustrated embodiment employs a structure where a distance FFT processor 651 is set up for each virtual antenna. It performs an FFT transform on the beat frequency signal from each chirped cycle, outputs the result, and accumulates and stores the results in a distance FFT buffer 653. Therefore, the distance FFT processor 651 should have the speed to fully process a single Fourier operation within at least one chirped cycle period.

[0144] The distance estimator 652 determines and outputs the beat frequency based on the signal output by the distance FFT processor 651. The distance estimator 652 can search for the location of the peak, i.e., the index of the maximum value in the spectrum stored in the distance FFT buffer 653, to identify the beat frequency and calculate the range from the beat frequency to the target.

[0145] The Doppler FFT processor 655 transforms the frequency components of the frequency domain signal output from the distance FFT processor 651 back into a frequency domain signal and outputs them. The Doppler FFT processor 655 performs the FFT transform by collecting the FFT coefficients stored in the distance FFT buffer 653 by frequency (i.e., by FFT index), thereby performing chirp-interval processing. The transformed FFT coefficients are stored in the Doppler FFT buffer 657.

[0146] In one embodiment, the Doppler FFT processor 655 includes an FFT transformer as many as the number of Fourier coefficients stored in the distance FFT buffer 653. As another example, a structure that repeatedly performs a Fourier transform can be employed.

[0147] Doppler FFT processor 655 receives and chirped cycle number N Loop The corresponding N of the same frequency Loop The system generates several output coefficients, performs an FFT transformation on them, and stores the transformed output coefficients in a Doppler FFT buffer 657. The values ​​stored in the Doppler FFT buffer 657 are range-Doppler spectrum values ​​obtained through range FFT and Doppler FFT.

[0148] The Doppler estimator 654 determines and outputs the Doppler frequency based on the signal output from the Doppler FFT processor 655. The Doppler estimator 654 can determine the Doppler frequency by identifying the position of an array that stores the peak values ​​of the distance-Doppler spectrum stored in the Doppler FFT buffer 657.

[0149] According to another aspect, the true value of the Doppler frequency can be determined based on the phase difference between chirps measured from at least three chirped signals located in consecutive time slots and having periods different from the measured values. Specifically, the true Doppler frequency can be determined by the Doppler frequency of the aliasing spectrum whose theoretically calculated phase difference has the most similar value to the measured phase difference.

[0150] Doppler frequency determiner 670 from such Figure 6 The wireless receiver 630 shown outputs at least three chirped signals located in consecutive time slots, measures the phase difference between the chirps, receives multiple Doppler frequencies 654 calculated by a Doppler estimator, and determines and outputs the Doppler frequency whose measured phase difference is closest to the theoretically calculated value as the true value from the multiple Doppler frequencies. Since previously referenced... Figure 11 These operations have been described, therefore their detailed descriptions will be omitted.

[0151] Figure 14 This is a block diagram illustrating the configuration of a Doppler frequency determiner according to an embodiment. As shown, the Doppler frequency determiner includes a phase difference meter 671, a search distance calculator 673, and a Doppler frequency searcher 675.

[0152] Phase difference meter 671 measures the phase difference represented by Equation 4, that is, the phase difference between at least three chimes located in consecutive time slots. These phase difference values ​​can be measured by detecting the start and end points of each chime and measuring the time difference between the ends located in consecutive time slots.

[0153] The Search Distance Calculator 673 determines the search distance for the Doppler frequencies of the aliased spectrum by comparing the maximum Doppler frequency of the target to be detected with the maximum Doppler frequency obtained from the distance Doppler spectrum.

[0154] The Doppler frequency searcher 675 determines and outputs the Doppler frequency that is most similar to the theoretically calculated phase difference value and the measured phase difference value from the Doppler frequencies of the aliasing spectrum corresponding to the search distance calculated by the search distance calculator 673.

[0155] First, at the target Doppler frequency, the phase difference between at least three chirped signals located in consecutive time slots and having different periods, included in the chirped cycle, is theoretically calculated, and a similarity value is calculated between the theoretically calculated value and the measured value measured by the phase difference meter 671. For all Doppler frequencies included in the aliasing spectrum within the search distance, the Doppler frequency with the maximum value among the calculated similarity values ​​is retrieved and output as the true Doppler frequency.

[0156] In reference Figure 11 The method described in the invention has already been described. Figure 14 The configuration operations are omitted here, so their detailed description will be omitted.

[0157] According to the present invention, existing limitations on the detectable radial velocity of targets in TDM FMCW radar equipment can be overcome. Furthermore, according to the present invention, position resolution can be improved by increasing the number of transmitting antennas in the TDM FMCW radar equipment. Additionally, the Doppler ambiguity problem can be solved while minimizing limitations in antenna design or minimizing the increase in frame length in the TDM FMCW radar equipment. Alternatively, according to the present invention, the Doppler ambiguity problem can be solved while minimizing limitations in antenna design and minimizing the increase in frame length in the TDM FMCW radar equipment.

[0158] The invention has been described above with reference to the accompanying drawings and embodiments, but is not limited thereto. Rather, the invention should be construed as including various modifications that will be apparent to those skilled in the art. The appended claims are intended to cover such modifications.

Claims

1. A signal processing method for a TDM FMCW radar device, the radar device having an antenna array, wherein transmitting antennas and receiving antennas are arranged such that a plurality of virtual antennas have the same position, the method comprising: A wireless transmission operation for transmitting an FMCW radar waveform signal, the FMCW radar waveform signal being configured such that at least three special chirps are located in consecutive time slots and have different periods, at least one of the at least three special chirps being included in the chirp cycle of each radar signal transmitted by the plurality of virtual antennas; The wireless receiving operation is used to demodulate the baseband FMCW radar signal from the FMCW radar waveform signal reflected by the target, sample the difference signal between the baseband FMCW radar signal and the transmitted signal, convert the difference signal into a digital signal, and output the digital signal. A spectrum analysis operation is used to determine and output the beat frequency and Doppler frequency from the signal output from the wireless reception operation; and The Doppler frequency determination operation is used to measure the phase difference between at least three specific chirps that are located in consecutive time slots, have different periods, and are received at the plurality of virtual antennas in the wireless reception operation, and to determine and output the true Doppler frequency based on the measured values ​​and the Doppler frequency output in the spectrum analysis operation. The Doppler frequency determination operation includes: A phase difference measurement operation is used to measure the phase difference between at least three specific chirps that are located in consecutive time slots and have different periods. The search distance calculation operation is used to determine the search distance for the Doppler frequencies of the aliased spectrum by the ratio of the maximum Doppler frequency of the target to the maximum Doppler frequency obtained from the distance Doppler spectrum; and The Doppler frequency search operation is used to determine and output the Doppler frequency from the Doppler frequencies of the aliased spectrum that is most similar to the theoretically calculated phase difference value and the measured phase difference value.

2. The method of claim 1, wherein the FMCW radar waveform signal transmitted in the wireless transmission operation is configured such that the at least three special chirps located in consecutive time slots differ in at least one aspect of the idle time between the special chirps or the ramp time of the special chirps.

3. The method of claim 2, wherein the at least three special chirps located in consecutive time slots are configured such that the sum of the difference in idle time between the special chirps and the difference in ramp time of the special chirps is limited by the maximum target detection rate of the target.

4. The method according to claim 1, wherein the spectrum analysis operation includes: The distance FFT processing operation is used to transform the digital signal output in the wireless receiving operation into a frequency domain signal in chirp units and output the frequency domain signal. The Doppler FFT processing operation is used to transform the same frequency components of the frequency domain signal output in the distance FFT processing operation back into a frequency domain signal, and output the frequency domain signal. The distance estimation operation is used to determine and output the beat frequency based on the signal output in the distance FFT processing operation; and The Doppler estimation operation is used to determine and output the Doppler frequency based on the signal output in the Doppler FFT processing operation.

5. The method according to claim 1, wherein in the Doppler frequency determination operation, The phase difference between the at least three special chirps is measured from the at least three special chirps, which are located in consecutive time slots and output in the wireless receiving operation. The Doppler frequency that is most similar to the theoretically calculated phase difference value and the measured phase difference value is determined as the true Doppler frequency and output.

6. A TDM FMCW radar device, comprising: An antenna array in which transmitting and receiving antennas are arranged such that multiple virtual antennas have the same position; A wireless transmitter configured to transmit an FMCW radar waveform signal, the FMCW radar waveform signal being configured such that at least three special chirps are located in consecutive time slots and have different periods, at least one of the at least three special chirps being included in the chirp cycle of each radar signal transmitted by the plurality of virtual antennas; A wireless receiver configured to demodulate a baseband FMCW radar signal from an FMCW radar waveform signal reflected from a target, sample the difference signal between the baseband FMCW radar signal and the transmitted signal, convert the difference signal into a digital signal, and output the digital signal. A spectrum analyzer configured to determine and output the beat frequency and Doppler frequency from the signal output by the wireless receiver; and A Doppler frequency determiner is configured to measure the phase difference between at least three specific chirps that are located in consecutive time slots, have different periods, and are received by the wireless receiver from the plurality of virtual antennas, and to determine and output the true Doppler frequency based on the measured values ​​and the Doppler frequency output by the spectrum analyzer. The Doppler frequency determiner includes: A phase difference measuring device is configured to measure the phase difference between the at least three specific chirps that are located in consecutive time slots and have different periods. A search distance calculator is configured to determine the search distance for the Doppler frequencies of the aliased spectrum by the ratio of the maximum Doppler frequency of the target to the maximum Doppler frequency obtained from the distance Doppler spectrum; and A Doppler frequency searcher is configured to determine and output the Doppler frequency from the Doppler frequencies of the aliased spectrum that is most similar to the theoretically calculated phase difference value and the measured phase difference value.

7. The TDM FMCW radar device of claim 6, wherein the FMCW radar waveform signal transmitted by the wireless transmitter is configured such that the at least three special chirps located in consecutive time slots differ in at least one aspect of the idle time between the special chirps or the ramp time of the special chirps.

8. The TDM FMCW radar device of claim 7, wherein the at least three special chirps located in consecutive time slots are configured such that the sum of the difference in idle time between the special chirps and the difference in ramp time of the special chirps is limited by the target's maximum detection rate.

9. The TDM FMCW radar device according to claim 6, wherein the spectrum analyzer comprises: A distance-based FFT processor is configured to transform the digital signal output by the wireless receiver into a frequency domain signal in chirps and output the frequency domain signal. A Doppler FFT processor is configured to transform the same frequency components of the frequency domain signal output in the distance FFT processing operation back into a frequency domain signal and output the frequency domain signal. A distance estimator is configured to determine and output the beat frequency based on the signal output by the distance FFT processor; and A Doppler estimator is configured to determine and output the Doppler frequency based on the signal output of the Doppler FFT processor.

10. The TDM FMCW radar device according to claim 6, wherein the Doppler frequency determiner measures the phase difference between special chirps from at least three special chirps, the three special chirps being located in consecutive time slots and output from the wireless receiver, and determines and outputs the Doppler frequency that is most similar to the theoretically calculated phase difference value and the measured phase difference value as the true Doppler frequency.

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