Radar apparatus, method, and program

Abstract

To improve noise resistance without using a super-resolution algorithm and to reduce a calculation load when making the phases of a received first band signal and a second band signal continuous.SOLUTION: A radar device includes a transmission unit that transmits a transmission signal and a reception unit that receives a reflection signal of the transmission signal, in which a signal in a second band different from a first band is transmitted following the signal in the first band as the transmission signal from the transmission unit, the signal in the first band and the signal in the second band are frequency-modulated pulse signals, and a calculation unit that executes processing of resampling a frequency spectrum of the signal in the second band received by the reception unit in a slow time axis direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a radar device, a method, and a program. [Background technology]

[0002] The range resolution of a radar device depends on the occupied bandwidth. From the perspective of effective use of frequency resources, it is difficult to actually occupy a wide bandwidth. One method to address this issue is band interpolation. This method involves transmitting and receiving radar waves in different frequency bands and estimating the spectrum between the frequency bands of the received signals to virtually secure a wide bandwidth and improve range resolution. For example, radar waves are transmitted and received in two frequency bands: 5.0 to 5.5 GHz (gigahertz) and 9.5 to 10.0 GHz. Band interpolation is then performed on the blank band of the 5.5 to 9.5 GHz frequency spectrum to expand the bandwidth as if observations were made in an ultra-wideband of 5.0 to 10.0 GHz.

[0003] The conditions for band interpolation are, for example: - The phase coherency of the received signals in each band is maintained, and - The distance between the radar and the target for each frequency band must be consistent. etc.

[0004] When a target is moving, the above conditions are generally not met. Therefore, before band interpolation is performed, the amount of phase shift and position shift (incoherence correction amount) of each received signal is estimated and corrected (this is also called "incoherence correction processing").

[0005] As an example of incoherence correction processing, for example, Patent Document 1 discloses a conventional radar device (Reference Document 1: U.S. Patent No. 5,945,940) that uses a super-resolution algorithm such as MUSIC (Multiple Signal Classification) to match the phases in the range direction of the spatial spectra of a first radar that observes in a first frequency band and a second radar that observes in a second frequency band, and then expands the band based on these spatial spectra, and a configuration that solves this problem. According to Patent Document 1, as shown in FIG. 11(A), the radar device of Reference Document 1 transmits and receives radar waves to and from a target using a transmitting / receiving antenna 1a of a first radar (Upper Sub-Band Radar) and a transmitting / receiving antenna 1b of a second radar (Lower Sub-Band Radar). Reference numerals 2a and 2b denote transceivers that transmit and receive signals in the first and second frequency bands. Figures 11(B) to (D) show the frequency spectrum of the received signal, with the horizontal axis representing the spatial frequency in the range direction (range frequency) or the instantaneous transmission frequency of the radar. In Figure 11(B), 101a and 101b represent the received signals of the first and second radars on the frequency spectrum, while in Figure 11(C), 102a and 102b represent the received signals of the first and second radars on the frequency spectrum at the output of a mutual coherence processing subsystem 3 that uses a super-resolution algorithm such as the MUSIC method to make the phases of 101a and 101b continuous. In Figure 11(D), 103 represents the spectrum of an ultra-wide band (UWB) signal output from a band interpolation and expansion means 4. A range compression means 5 performs range compression (pulse compression) on the signal expanded by the band interpolation and expansion means 4, and a display means 6 displays and outputs the target.

[0006] The range resolution of the first and second radars is determined by the spectral bandwidth of signal 101a and signal 101b, respectively; the wider these bandwidths are, the higher the range resolution can be achieved. Therefore, the spectrum of these signals observed by the two radars is interpolated or extrapolated to expand the spectral bandwidth. To do this, it is necessary to maintain the phase coherency of signal 101a and signal 101b.

[0007] However, as shown in Figure 11(B), this condition does not generally hold. This is because the distances from the phase centers of the two radar antennas 1a and 1b to the target generally do not match perfectly. To solve this problem, in Reference 1, a mutual coherence processing subsystem 3 compensates for signal 101a to obtain signal 102a so that the phases of signals 101a and 101b become coherent in the frequency spectrum. In order to estimate the amount of position and phase shift of the signals observed by each radar, a super-resolution algorithm such as the MUSIC method is applied to the signals from each radar before signal synthesis.

[0008] However, to perform accurate positioning and phasing and to successfully interpolate and extend the band, it is necessary to accurately estimate and compensate for the positioning and phasing. The radar device in Reference 1 has poor correction accuracy in environments with a low signal-to-noise ratio (SNR), and the performance of band interpolation and extension is significantly reduced.

[0009] To address this problem, Patent Document 1 provides a system that includes multiple radars that observe targets in different frequency bands, a covariance matrix estimation means that estimates a covariance matrix in signal space for each radar signal, a covariance matrix synthesis means that synthesizes the estimated covariance matrices for each radar signal, and a super-resolution range compression means that uses the synthesized covariance matrix to estimate a high-resolution range profile with a super-resolution algorithm, making it possible to estimate and correct position and phase shifts in incoherence correction processing without using a super-resolution algorithm for each radar signal. In Patent Document 1, in order to improve the accuracy of the positional deviation amount τ, for example, a forward-backward spatial smoothing method is used to calculate a composite covariance matrix R(τ) for each of the first radar signal and the second radar signal, the spread of the eigenvalues ​​of R(τ) is measured using entropy, the positional deviation amount that minimizes the entropy value is taken as an estimated value, and a super-resolution range profile is estimated using a super-resolution algorithm such as the Capon method or the MUSIC method for the composite covariance matrix using the estimated value. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-042372 Summary of the Invention [Problem to be solved by the invention]

[0011] As described above, in Patent Document 1, when a super-resolution algorithm is used for incoherence correction processing, in a low SNR environment, the correction accuracy is poor and the performance of band interpolation and expansion is significantly reduced (i.e., noise resistance is poor). In order to solve this problem, a brute force process is performed instead of using a super-resolution algorithm, which results in a high calculation load.

[0012] The present disclosure has been devised in view of the above-mentioned problems, and its purpose is to provide a radar device, method, and program that improves noise resistance and reduces the computational load when making the phases of received first and second band signals coherent without using a super-resolution algorithm. [Means for solving the problem]

[0013] An example of a radar device according to the present disclosure includes a transmitter that transmits a transmission signal and a receiver that receives a reflected signal of the transmission signal, wherein the transmission signals from the transmitter include a signal in a first band followed by a signal in a second band different from the first band, the first band signal and the second band signal being frequency-modulated pulse signals, and a calculation unit that executes processing to resample the frequency spectrum of the signal in the second band received by the receiver in a slow-time axis direction.

[0014] Furthermore, as an example of a method of the present disclosure, a processing method of a radar device in which a signal in a first band is transmitted as a transmission signal from a transmitter, followed by a signal in a second band different from the first band, the first band signal and the second band signal being frequency-modulated pulse signals, and a reflected signal of the transmission signal is received by a receiver is provided, the processing method comprising: resampling the frequency spectrum of the signal in the second band received by the receiver in a slow time axis direction.

[0015] Furthermore, as an example of a program of the present disclosure, a radar device in which a signal in a first band is followed by a signal in a second band different from the first band as a transmission signal from a transmitting unit, the first band signal and the second band signal being frequency-modulated pulse signals, and a receiving unit receives a reflected signal of the transmission signal, is exemplified as an example of a program executed by a processor of the radar device, the program causing the processor to execute a process of resampling the frequency spectrum of the signal in the second band received by the receiving unit in the slow time axis direction. [Effects of the Invention]

[0016] According to the present disclosure, when the received first band signal and second band signal are made coherent, a super-resolution algorithm is not used, thereby improving noise resistance and reducing the amount of calculation. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration example of a radar device according to the present disclosure. [Figure 2] FIG. 2 is a diagram illustrating an example of a transmission signal according to the present disclosure. [Figure 3] FIG. 2 is a diagram illustrating an example of the configuration of a calculation unit according to the present disclosure. [Figure 4] 1A and 1B are diagrams for schematically explaining Fourier transform processing in the present disclosure. [Figure 5] FIG. 2 is a diagram illustrating a functional configuration of an incoherence correction processing unit according to the present disclosure. [Figure 6] 1A and 1B are diagrams illustrating a schematic diagram of an incoherence correction process according to the present disclosure. [Figure 7] 1A and 1B are diagrams illustrating a schematic diagram of an incoherence correction process according to the present disclosure. [Figure 8] FIG. 10 is a diagram illustrating a schematic diagram of another example of the configuration of a radar device according to the present disclosure. [Figure 9] 1A and 1B are diagrams for schematically explaining Fourier transform processing in the present disclosure. [Figure 10] FIG. 2 is a diagram illustrating an example of implementation of a calculation unit according to the present disclosure. [Figure 11] (A) to (D) are diagrams illustrating Reference Document 1. DETAILED DESCRIPTION OF THE INVENTION

[0018] According to one or more embodiments of the present disclosure, an incoherence correction process is proposed that makes it possible to improve noise resistance and reduce calculation load by converting a first band signal and a second band signal into waveforms with aligned phases (coherent), without using a super-resolution algorithm or a brute force method as in Patent Document 1.

[0019] 1 is a schematic diagram illustrating an example of the configuration of a radar device according to the present disclosure. The radar device 10 is a device for detecting the presence of a target 20 and measuring the distance thereto using radio waves. The radar device 10 includes a transmitting antenna 11 that transmits radio waves (radar waves), a receiving antenna 12 that receives the radio waves (radar waves) reflected by the target 20, a transmitting unit 110 that generates a transmission signal and outputs the radio waves (radar waves) from the transmitting antenna 11, a receiving unit 120 that performs reception processing of the radio waves (radar waves) received by the receiving antenna 12, a calculation unit 140 that performs distance measurement processing based on the reception signal from the receiving unit 120, and a display processing unit 150 that displays the distance measurement results.

[0020] The transmitting unit 110 includes a transmitting waveform generating unit (not shown) that generates a transmitting pulse. The transmitting unit 110 outputs a transmitting pulse in a first band (low band side) that is a low sub-band of an ultra-wide band (UWB) and a transmitting pulse in a second band (high band side) that is a high sub-band, and outputs radio waves (radar waves) from the transmitting antenna 11.

[0021] 2 is a diagram illustrating an example of a transmission pulse waveform in the present disclosure. The vertical axis of FIG. 2 represents frequency, and the horizontal axis represents time. The transmitting unit 110 generates a pulse (the (2k-1)th pulse (k=1, 2, ...)) in the first band (low band side) and a pulse (the 2kth pulse (k=1, 2, ...)) in the second band (high band side), and transmits them from the transmitting antenna 11.

[0022] The transmission pulse is a chirp signal of Linear Frequency Modulation (LFM). The transmission pulse on the low band side of the odd-numbered pulse is a constant frequency change rate b for the period of pulse width To from the start of frequency sweep (frequency sweep period). TIFF2026026713000002.tif15153 …(1) The frequency increases linearly with B0, where B0 is the subband bandwidth.

[0023] In FIG. 2, T1 is the period when the frequency is swept at a frequency change rate b in the blank band B1 between the low band side and the high band side, and is given by: TIFF2026026713000003.tif15153 …(2)

[0024] therefore, TIFF2026026713000004.tif10150…(3)

[0025] After a predetermined time Δt (any value of Δt) has elapsed following T1, the frequency sweep of the even-numbered pulse (high-band side) transmission pulse begins, and a high-band side pulse with pulse width T0 is transmitted. After that, after T2 has elapsed, the next low-band side pulse (third pulse) is transmitted.

[0026] Although not particularly limited, in the example shown in FIG. 2, the pulse repetition interval (PRI) time T PRI teeth, TIFF2026026713000005.tif11153…(4) is.

[0027] In addition, in Figure 2, T2=T1…(5) 2, Δt is not limited to Δt>0, and may also include Δt=0.

[0028] In the example of Figure 2, the low-band, blank band, and high-band are continuous on the frequency axis. For example, if the frequency bands of the low-band pulse and the high-band pulse are 5.0 to 5.5 GHz (bandwidth 500 MHz (mega-hertz)) and 9.5 to 10.0 GHz (bandwidth 500 MHz), respectively, the blank band is 4 GHz from 5.5 to 9.5 GHz. Also, the center frequency f of the low-band pulse is cL is 5.25GHz, and the center frequency of the high-band pulse is f cH is 9.75GHz.

[0029] The transmitting antenna 11 transmits the low-band pulse and the high-band pulse output from the transmitting unit 110 as radio waves (radar signals), and the receiving antenna 12 receives the signal reflected by the target 20. The receiving unit 120 frequency-converts the RF (Radio Frequency) signal received by the receiving antenna 12 to a baseband signal (analog signal), converts it to a digital signal using an AD (Analog-to-Digital) converter (not shown), and inputs it to the calculating unit 140.

[0030] As shown in FIG. 3, the calculation unit 140 includes a pulse compressor 141, a range walk correction processor 142, an incoherence correction processor 143, a coherent integrator 144, and a band interpolator 145.

[0031] Transmit pulse s t (t) is expressed in complex notation as in the following equation (6). TIFF2026026713000006.tif15153 …(6)

[0032] TIFF2026026713000007.tif16150…(7)

[0033] where T0 is the pulse width, B0 is the subband width, rect(x) is the window function (1 when |x|<1 / 2, 0 when |x|>1 / 2), ω c is the carrier angular frequency (ω c =2πf c :f c is the carrier frequency. In the low band, f_c =f _cL , when it is in the high band, f_ c =f _cH ), j is the imaginary unit (j 2 =-1).

[0034] If the time from when the pulse output by the transmitter 110 is transmitted as a radio wave (radar signal) from the transmitting antenna 11 to when it is reflected by the target 20 and received by the receiving antenna 12 is τ0, then: TIFF2026026713000008.tif15153 …(8)

[0035] c is the speed of light, R(t k ) is the distance between the target 20 and the radar device 10. k is the time when the pulse is transmitted. The time when the pulse is transmitted is called slow time. The time that has elapsed since the time when the pulse was transmitted is called fast time.

[0036] Received signal waveform r (t, t k ) (k=1, 2, 3, ...) is expressed in complex notation (0 Hz of the baseband signal is fc of the RF signal) as shown in the following equation (9), where t is the fast time.

[0037] TIFF2026026713000009.tif48156 …(9)

[0038] Fig. 4 is a diagram showing an example of the relationship between a received signal and an FFT (Fast Fourier Transform) for the transmitted signal shown in Fig. 2. As shown in Fig. 4, when the FFT is performed on the received signal in sections such as the first pulse and the second pulse, the third pulse and the fourth pulse, etc., the received signal s' before the FFT is r (t,t k) (k=1, 3, 5, ...). In Figure 4, the reception time of the kth pulse (k=1, 2, 3, 4, 5, 6, ...) is represented as tk to clarify that it corresponds to the transmission time tk (slow time) of the kth pulse (k=1, 2, 3, 4, 5, 6, ...) in Figure 2 and to simplify the equation.

[0039] The received signal of the (k+1)th pulse (k+1=2,4,6, …) is smaller than the received signal of the kth pulse (k=1,3,5, …) at T=t k+1 -t k (k=1,3,5,...) in the fast time direction. Also, the RF (Radio Frequency) signal corresponding to 0 Hz of the baseband signal is shifted to, for example, (f cH +f cL ) / 2, then the kth pulse (k=1,3,5,...) is -(f cH -f cL ) / 2, and the (k+1)th pulse is shifted by (f cH -f cL ) / 2 to shift the frequency.

[0040] Signal s' is a combination of the frequency-shifted k-th pulse (k=1,3,5,...) and the (k+1)-th pulse (k+1=2,4,6,...). r (t,t k ) is given by the following equation (10):

[0041] TIFF2026026713000010.tif11150…(10)

[0042] The frequency shift of the kth pulse (k=1, 3, 5, ...) and the (k+1)th pulse (k+1=2, 4, 6, ...) may be performed in the calculation unit 140 as pre-processing for the pulse compression unit 141 (or may be performed in the receiving unit 120).

[0043] Next, we will explain pulse compression by pulse compression unit 141. Pulse compression is usually performed by multiplying the frequency spectrum obtained by Fourier transforming a signal in the time domain by the frequency spectrum of a reference signal, but below we will explain it using a convolution operation in the time domain.

[0044] Reference signal s(t,t k ) (k=1,3,5,...) is given by the following equation (11): s' r (t,t k ) as well as the calculation of T=t k+1 -t k Shift the kth pulse in the fast time direction by (k=1,3,5,...) and the kth pulse is -(f cH -f cL ) / 2, the k+1th pulse is (f cH -f cL ) / . The reference signal s(t,t k ) is obtained by combining the frequency-shifted kth pulse (the first term on the right-hand side of equation (11)) and the frequency-shifted k+1th pulse (the second term on the right-hand side of equation (11)).

[0045] TIFF2026026713000011.tif11150…(11)

[0046] Pulse compression in the time domain is performed using this reference signal s(t,t k ) and the signal s' in Eq. (10) r (t,t k ) and is given by the following equation (12).

[0047] TIFF2026026713000012.tif15153 TIFF2026026713000013.tif18150TIFF2026026713000014.tif18153 …(12)

[0048] In equation (12), s * (t,t k ) is s(t,t k), where k in tk is an odd number (k=1, 3, 5, …). The sinc function is given by: sinc(x)=sin(x) / x …(13)

[0049] In equation (12), the first term corresponds to the low-frequency side, and the second term corresponds to the high-frequency side. The function sinc(x) has a peak at x = 0, so it has a peak at τ = 2R(tk) / c on the low-frequency side (target distance = R(t k )) and the high-band side is τ=2R(t k +T) / c (target distance = R(t k +T)). Each pulse has a different target distance (range walk).

[0050] The range walk correction processing unit 142 performs range walk correction processing on the pulse compression result. The pulse compression result φ(τ,t k )(k=1,3,5,…) is the Fourier transform of S(f, t k ) (k=1,3,5,...), it can be expressed by the following equation (14).

[0051] TIFF2026026713000015.tif11153 TIFF2026026713000016.tif16150 TIFF2026026713000017.tif16150…(14)

[0052] In equation (14), the first term is the low-band side (kth pulse) (k=1, 3, 5, ...), and the second term is the high-band side ((k+1)th pulse) (k+1=2, 4, 6, ...). In the exponential function exp() of the first and second terms of equation (14), among the terms that include the range frequency f, TIFF2026026713000018.tif9150…(15) represents the target distance for each pulse on the low-band and high-band sides (on the low-band side, R(t k) ), and in the high-band, R(t k+T)). The target distances are different for each pulse on the low and high band sides (range walk).

[0053] where: TIFF2026026713000019.tif11153…(16) (however, TIFF2026026713000020.tif6150…(17) TIFF2026026713000021.tif12150…(18) ) Then, S(f, t k ) (k=1,3,5,...) can be expressed by the following equation (19).

[0054] TIFF2026026713000022.tif16150 TIFF2026026713000023.tif16150…(19) where T= t k+1 -t k

[0055] S(f, t) in equation (19) k )(k=1,3,5,…) for Keystone transformation (slow-time resampling): TIFF2026026713000024.tif16150…(20) Executing this, the following equation (21) is derived.

[0056] TIFF2026026713000025.tif16150 TIFF2026026713000026.tif16150…(21) Here, k is an odd number (k=1, 3, 5, ...).

[0057] In the exponential function exp() of the first and second terms on the right side of equation (21), among the terms that include the range frequency f, TIFF2026026713000027.tif9150…(22) represents the target distance for each pulse on the low and high frequency bands. The target distance for each pulse on the low and high frequency bands is the same value (r), which indicates that range walk has been corrected.

[0058] However, as can be seen by comparing the first and second terms on the right-hand side of equation (21), the exponential function exp of the second term is the exponential function exp of the first term. TIFF2026026713000028.tif15150…(23) That is, there is a time T (=t k+1 -t k ) corresponding phase difference TIFF2026026713000029.tif14150…(24) exists and is not coherent.

[0059] Therefore, in order to make the phases of the low band side (k-th pulse) (k=1, 3, 5, ...) and the high band side ((k+1)-th pulse) (k+1=2, 4, 6, ...) coherent, the incoherence correction processing unit 143 leaves the low band side (k-th pulse) (k=1, 3, 5, ...) as it is, and resamples the high band side ((k+1)-th pulse) (k+1=2, 4, 6, ...) by -T in the slow time direction, as follows: As a result, the phase of the high band side ((k+1)-th pulse) (k+1=2, 4, 6, ...) is changed by the phase of the low band side (k-th pulse) (k=1, 3, 5, ...). TIFF2026026713000030.tif15150…(25) (the phase difference is 0), and the signals are coherent.

[0060] As shown in Fig. 5, the incoherence correction processing unit 143 includes a Fourier transform unit 146, a resampling processing unit 147, and an inverse Fourier transform unit 148. In Fig. 5, when the range walk correction processing unit 142 outputs a time domain signal, the Fourier transform unit 146 converts this into a frequency domain signal, but is not required when the range walk correction processing unit 142 outputs the frequency domain signal represented by equation (21).

[0061] The resampling processing unit 147 calculates S'(f,t k ) (k=1,3,5,...) the following process is performed. k )(k=1,3,5,…), the frequency range (low band side):-(f cH -f cL ) / 2-B0 / 2≦f≦-(f cH -f cL ) / 2+B0 / 2 is left as it is (Equation (26)), and the frequency range (high band side): (f cH -f cL ) / 2-B0 / 2≦f≦(f cH -f cL ) / 2+B0 / 2, in the slow time direction -T(=-(t k+1 -t k )) (Equation (27)).

[0062] TIFF2026026713000031.tif9150…(26)

[0063] TIFF2026026713000032.tif9150…(27)

[0064] Figure 6 shows the frequency spectrum of the high-frequency band (the (k+1)th pulse (k=1,3,5,...)) along the slow time axis, -T(=-(t k+1 -t k )) Schematic diagram of a shifting resampling process.

[0065] This resampling process reduces S'(f,t k )(k=1,3,5,…) is TIFF2026026713000033.tif6150 TIFF2026026713000034.tif35156 …(28) The low-band side (k-th pulse) (k=1,3,5,...) and the high-band side ((k+1)-th pulse) (k+1=2,4,6,...) have the same functional form except for rect(). In other words, the high-band side ((k+1)-th pulse) (k+1=2,4,6,...) has the same phase (equation (25)) as the low-band side (k-th pulse) (k=1,3,5,...), and are coherent.

[0066] FIG. 7 shows a schematic diagram of a frequency spectrum 801 on the low-band side (k=1st pulse) and a frequency spectrum 802 on the high-band side (k+1=2nd pulse), in which a coherent frequency spectrum 803 is obtained by synthesizing the frequency spectrum 801 with the frequency spectrum 802 shifted by −T in the slow-time direction (the second pulse after resampling).

[0067] The inverse Fourier transform unit 148 converts the frequency spectrum S″(f,t k ) (k=1,3,4,…) into a time domain signal.

[0068] In the coherent integrator 144, when the CPI (Coherent Pulse Interval or Coherent Processing Interval) is n×PRI, n received pulse trains (pulses on the low frequency side and high frequency side with incoherence corrected) of the received signal are coherently integrated in the slow time direction (integration in the time domain: phase-aligned and added together). The signal power is n 2 The power of the white noise is multiplied by n, and the signal-to-noise ratio (SNR) is multiplied by n.

[0069] 11(A), the band interpolation processing unit 145 performs band interpolation processing using a super-resolution algorithm such as the well-known MUSIC method or Matrix Pencil method to improve the distance resolution. The band interpolation processing unit 145 interpolates the phase of a blank band between the low-band side and the high-band side in the frequency spectrum in which the phase coherency of the pulses on the low-band side and the pulses on the high-band side is ensured by the incoherence correction processing unit 143, and generates, for example, the frequency spectrum 103 of the ultra-wide band (UWB) signal shown in FIG. 11(D) above.

[0070] The display processing unit 150 displays the distance measurement results of the target. Note that, in the present disclosure, the pulse compression unit 141 may be configured to operate after the band interpolation processing unit 145.

[0071] This disclosure provides slow time t k (k=odd number) and t k+1 (T=t k+1 -t k On the receiving side of the low-band pulse and the high-band pulse of the frequency modulation (same frequency bandwidth, same frequency change rate) respectively transmitted by the FM tuner, the frequency spectrum of the high-band pulse is resampled so as to shift it back by time T, so that the phase of the received low-band pulse and the phase of the received high-band pulse separated from the low-band by a blank band can be made coherent.

[0072] In the present disclosure, as schematically shown in Fig. 8, a configuration may be adopted in which transceiver units 131 and 132 are provided for transmitting pulses on the high band side and for transmitting pulses on the low band side. Transmitter unit 111 of transceiver unit 131 outputs transmission pulses in a first band (low band side) that is a low sub-band of ultra-wideband (UWB), and transmitter unit 112 of transceiver unit 132 outputs transmission pulses in a second band (high band side) that is a high sub-band, and the pulses of the first band (low band side) and the second band (high band side) are mixed by a diplexer or the like (not shown) and output from transmitting antenna 160. The received signal received by the receiving antenna 170 is separated into signals of a first band and a second band by a diplexer not shown, and the receiving unit 121 of the transmitting / receiving unit 131 receives pulses of the first band (low band side), and the receiving unit 122 of the transmitting / receiving unit 132 receives pulses of the second band (high band side).

[0073] Although not particularly limited, the calculation unit 140 may, for example, as shown in FIG. 9, perform a Fourier transform on the low-band side (k-th pulse) (k=1, 3, 5, ...) received signal received by the receiving unit 121, and a Fourier transform on the high-band side ((k+1)-th pulse) (k+1=2, 4, 6, ...) received signal received by the receiving unit 122.

[0074] Pulse compression may be performed by conjugate multiplying a Fourier transform of the received signal for the kth pulse (k=1, 3, 5, ...: low-band side) with a Fourier transform of a reference signal for the low-band side pulse, and by conjugate multiplying a Fourier transform of the received signal for the (k+1)th pulse (high-band side) with a Fourier transform of a reference signal for the high-band side pulse. Range walk correction processing may be performed on the pulse-compressed frequency spectrum of the kth pulse (k=1, 3, 5, ...: low-band side) and the pulse-compressed frequency spectrum of the (k+1)th pulse (high-band side) with respect to the range frequency and slow time axes, and resampling (interpolation) may be performed so as to shift the frequency spectrum of the received signal for the (k+1)th pulse (high-band side) by time −T in the slow time axis direction, thereby aligning the phase of the received signal for the kth pulse (low-band side) with the phase of the received signal for the (k+1)th pulse (high-band side).

[0075] In the above embodiment, the frequency bands of the transmission (reception) pulses are two, a low band side and a high band side, but the present invention can also be applied to cases where there are three or more types, similar to the above embodiment.

[0076] FIG. 10 is a diagram illustrating a configuration when implemented in a computer device (data processing device, processor device) 40. Referring to FIG. 10, the computer device 40 includes a processor 41, a memory 42 such as a semiconductor memory (e.g., a random access memory (RAM), a read-only memory (ROM), or an electrically erasable programmable read-only memory (EEPROM)) (or a hard disk drive (HDD) or a solid state drive (SSD)), a display device 43, and an interface 44 (bus interface) that connects to the receiving unit 120 of FIG. 1. The processor 41 executes the program stored in the memory 42 to perform the processing of the calculation unit 140 and the display processing unit 150 of FIG. 1. The processor 41 may also include a digital signal processor (DSP) for FFT and IFFT calculations. The display device 43 displays the distance results on a screen.

[0077] For range walk correction, the following references are referred to, for example: [Reference 2] RP Perry, RC DiPietro, RL Fante, "Coherent Integration With Range Migration Using Keystone Formatting", [Retrieved April 19, 2023], Internet<URL:https: / / www.mitre.org / sites / default / files / pdf / 07_0017.pdf> [Reference 3] MA Richards, "The Keystone Transformation for Correcting Range Migration in Range-Doppler Processing" [Retrieved May 7, 2023], Internet<URL:https: / / radarsp.weebly.com / uploads / 2 / 1 / 4 / 7 / 21471216 / keystone_commutative.pdf>

[0078] The disclosures of the above patent documents and references are incorporated herein by reference. Modifications, adjustments, and combinations of the embodiments and examples are possible within the scope of the disclosure (including the claims) of this application, and further based on the basic technical ideas thereof. Furthermore, various combinations and selections of the various disclosed elements (including each element of each claim, each element of each example, each element of each drawing, etc.) are possible within the scope of the claims of this disclosure. In other words, this disclosure naturally includes various modifications and alterations that would be possible for a person skilled in the art based on the entire disclosure, including the claims, and the technical ideas thereof. [Explanation of symbols]

[0079] 1a, 1b Transmitting and receiving antennas 2a, 2b Transceiver 3 Mutual coherence means 4 Band Interpolation and Expansion Methods 5 Range Compression Methods 6 Display means 10 Radar equipment 11 Transmitting Antenna 12 receiving antenna 20 goals 40 Computer Equipment 41 processors 42 memory 43 Display device 44 Interface 101a, 101b First and second radar reception signals 102a, 102b: First and second radar reception signals 103 Spectrum of Ultra-Wideband Signals 110, 111, 112 Transmitting unit 120, 121, 122 Receiver 130 Transmitter / Receiver 131 Low-band pulse transmitter / receiver 132 High-band pulse transmitter / receiver 140 Arithmetic section 141 Pulse Compression Section 142 Range walk correction processing unit 143 Incoherence correction processing unit 144 Coherent Integration Section 145 Band interpolation processing unit 146 Fourier transform section 147 Resampling processing section 148 Inverse Fourier Transform 150 Display processing unit 160 transmitting antenna 170 receiving antenna 801, 802, 803 frequency spectrum

Claims

1. a transmitter that transmits a transmission signal; a receiving unit that receives a reflected signal of the transmission signal, The transmission signal includes: a signal in a first band is transmitted followed by a signal in a second band different from the first band; the first band signal and the second band signal are frequency modulated pulse signals; a calculation unit that executes a process of resampling the frequency spectrum of the signal in the second band received by the receiving unit in a slow time axis direction.

2. 2. The radar device according to claim 1, wherein the calculation unit shifts the frequency spectrum of the second band signal by a time period corresponding to a difference between a transmission time of the second band signal and a transmission time of the first band signal, thereby making the phase of the first band signal and the phase of the second band signal coherent.

3. the calculation unit performs range walk correction on a set of a plurality of frequency spectra along a slow time axis of the first band signal and the second band signal received by the receiving unit; The radar device according to claim 2 , wherein the resampling is performed in the slow-time axis direction on the frequency spectrum of the range-walk-corrected second band signal.

4. 2. The radar device according to claim 1, wherein the calculation unit performs a predetermined amount of frequency shift on the first band signal and the second band signal, and performs pulse compression on the frequency-shifted first band signal and the frequency-shifted second band signal.

5. 2. The radar device according to claim 1, wherein the calculation unit performs coherent integration on the first band signal and the second band signal, the phases of which have been made coherent by the resampling, and further performs band interpolation between the first band and the second band.

6. the first band, the blank band, and the second band are adjacent to each other on a frequency axis, the first band signal and the second band signal are linear frequency modulated pulse signals; 6. The radar device according to claim 1, wherein a frequency sweep of the second band signal at the frequency change rate is started when a predetermined time has elapsed from a time point at which a frequency sweep of the first band signal has ended, the time being equal to a time required for frequency sweeping the blank band at the same frequency change rate as the first band, plus a predetermined time.

7. a signal in a first band followed by a signal in a second band different from the first band is transmitted as a transmission signal from a transmitter, and the first band signal and the second band signal are frequency-modulated pulse signals; A processing method in a radar device in which a receiving unit receives a reflected signal of the transmission signal, comprising: A processing method for a radar device, comprising: performing a process of resampling the frequency spectrum of the second band signal received by the receiving unit in a slow time axis direction.

8. 8. The processing method for a radar device according to claim 7, wherein the resampling shifts the frequency spectrum of the second band signal by a time period corresponding to a difference between a transmission time of the second band signal and a transmission time of the first band signal, thereby making the phase of the first band signal and the phase of the second band signal coherent.

9. performing range walk correction on a set of a plurality of frequency spectra along a slow time axis of the first band signal and the second band signal received by the receiving unit; 8. The processing method for a radar device according to claim 7, wherein the resampling is performed on the frequency spectrum of the range-walk-corrected second band signal in a slow-time axis direction.

10. a signal in a first band followed by a signal in a second band different from the first band is transmitted as a transmission signal from a transmitter, and the first band signal and the second band signal are frequency-modulated pulse signals; A processor of a radar device that receives a reflected signal of the transmitted signal at a receiving unit, a program for executing a process of resampling the frequency spectrum of the second band signal received by the receiving unit in a slow time axis direction;

Images