WO2023073763A1 - Radar device - Google Patents

Abstract

A radar device (100) according to the present disclosure comprises: a pulse repetition interval (PRI) controlling unit (150) which sets a predetermined PRI for each hit; a signal generating circuit (110) which continuously generates a plurality of transmission pulse signals at a timing based on the PRI; a transmitting and receiving unit (120) which transmits the transmission pulse signals to an exterior space and receives, from the exterior space, a plurality of reflected wave signals corresponding respectively to the transmission pulse signals; a receiving circuit (140) which generates a plurality of reception signals corresponding respectively to the transmission pulse signals by sampling each of the reflected wave signals received by the transmitting and receiving unit (120); a correlation processing unit (161) which carries out pulse compression on the reception signals by means of a correlation operation; a compensation processing unit (162) which performs motion compensation using a predetermined speed candidate; a target candidate detecting unit (163) which detects a target candidate on the basis of a signal after processing by the compensation processing unit (162); and a speed/distance measuring unit (164) which estimates an unambiguous speed and distance of a target using results from the target candidate detecting unit which were processed using a plurality of motion compensation candidates in an interval wider than a speed interval in which measurement without ambiguity is possible.

Description

radar equipment

The technology disclosed herein relates to a radar device and a signal processing method for the radar device.

There are various types of radar equipment. For example, there is a radar device of the pulse Doppler system that transmits a plurality of pulse waves toward a target based on a pulse repetition interval (PRI) and detects the distance and speed of the target.

The technology related to the pulse Doppler radar device can be seen in Patent Document 1, for example. Patent Literature 1 discloses a technique related to a radar apparatus that performs high-accuracy Doppler correction even when ambiguity occurs, and improves super-resolution ranging accuracy.

JP 2010-281605 A

Velocity measurement by a radar device has a narrow velocity interval that can be solved without ambiguity if the PRI is long assuming a target that is far away and moves at high speed. For this reason, under such circumstances, it is necessary to widen the velocity interval between assumed targets. In addition, in order to obtain the maximum intensity of the target signal with high accuracy, it is necessary to finely divide the speed compensation candidates, which increases the computational load. In the method of resolving speed ambiguities by searching described in Patent Document 1, there is a trade-off relationship between the accuracy of solving without ambiguities and the amount of computation required for the search.

The disclosed technology is intended to solve the above problems, and aims to obtain a speed measuring means capable of achieving high accuracy and reducing the amount of calculation even if the speed interval is wide.

A radar device according to the technology disclosed herein includes a PRI control unit that sets a predetermined pulse repetition period for each hit, a signal generation circuit that continuously generates a plurality of transmission pulse signals at timing based on the pulse repetition period, A transmitting/receiving unit that transmits a transmitted pulse signal to an external space and receives a plurality of reflected wave signals corresponding to each of the transmitted pulse signals from the external space; a receiving circuit for generating a plurality of received signals respectively corresponding to the transmitted pulse signals; a correlation processing unit for pulse-compressing the received signals by correlation calculation; a compensation processing unit for performing motion compensation based on preset speed candidates; A target candidate detector that detects a target candidate based on the processed signal of the processor, and a target processed using a plurality of motion compensation candidates that are spaced wider than an unambiguously measurable velocity interval (Δν _amb ). a velocimetry and range finder for estimating the unambiguous velocity and range of the target from the results from the candidate detectors.

Since the radar device according to the technology disclosed herein has the above configuration, the target speed can be estimated accurately while reducing the computational load based on a plurality of speed candidates in a wide range in which speed ambiguities appear. be able to.

FIG. 1 is a block diagram showing the functional configuration of a radar device according to the technology disclosed herein. FIG. 2 is a block diagram showing the functional configuration of the radar signal processing circuit 160 of the radar device according to Embodiment 1. As shown in FIG. FIG. 3 is a block diagram showing the functional configuration of the signal generation circuit 110 of the radar device according to the first embodiment. FIG. 4 is a flow chart showing processing steps of the radar signal processing circuit 160 of the radar device according to the first embodiment. FIG. 5 is a graph showing an image of the detected intensity distribution in the speed interval without ambiguity and the speed compensation candidate. FIG. 6 is a graph representing an assumed velocity interval of a target, an ambiguity-free velocity interval, and an image of a target candidate. FIG. 7 is a graph showing an image in which speed and distance of peak intensity of each speed compensation candidate are superimposed. FIG. 8 is a graph showing an image of calculating an estimated target speed from the peak intensity of each speed compensation candidate. FIG. 9 is a graph showing an image of calculating the estimated distance from the estimated speed of the target. FIG. 10 is an image diagram showing the relationship between the ratio of sum signal to difference signal with respect to signal intensity and speed. FIG. 11 is a hardware configuration diagram of the signal processing circuit 170 of the radar device according to the technology disclosed herein. FIG. 12 is a block diagram showing the functional configuration of the radar signal processing circuit 160 (160B) of the radar device according to the second embodiment. FIG. 13 is a flow chart showing processing steps of the radar signal processing circuit 160 (160B) of the radar device according to the second embodiment. FIG. 14 is a flow chart showing the details of the CZT pulse Doppler processing step (ST165) in the flow chart shown in FIG. FIG. 15 is a block diagram showing the functional configuration of the radar signal processing circuit 160 (160C) of the radar device according to the third embodiment. FIG. 16 is a flow chart showing processing steps of the radar signal processing circuit 160 (160C) of the radar device according to the third embodiment. FIG. 17 applies the image diagram shown in FIG. 8 to the third embodiment. FIG. 18 is the image diagram shown in FIG. 9 applied to the third embodiment. FIG. 19 is a block diagram showing the functional configuration of the radar signal processing circuit 160 (160D) of the radar device according to the fourth embodiment. FIG. 20 is a flow chart showing processing steps of the radar signal processing circuit 160 (160D) of the radar device according to the fourth embodiment. FIG. 21 is a reference diagram showing an image of integration performed by the pulse-to-pulse stagger integration unit 167 according to the fourth embodiment.

The radar device 100 according to the technique of the present disclosure is of a pulse Doppler system that transmits a plurality of pulse waves toward a target based on a pulse repetition interval (PRI) and detects the distance and speed of the target. .
The radar device 100 according to the technology disclosed herein will be clarified by the description along the drawings for each embodiment. In addition, in the formulas included in the explanation, a proviso is shown after for. In almost all proviso variables are integer serial numbers and their ranges are given. Variables are shown as m, h, q, k, etc., but their usage and range are the same for one variable unless otherwise specified. Also, in some formulas, the proviso related to the explanation of the variables may be omitted.

Embodiment 1.
FIG. 1 is a block diagram showing a functional configuration of a radar device 100 according to technology disclosed herein. As shown in FIG. 1 , the radar device 100 includes a signal generation circuit 110 , a transmission/reception section 120 , an antenna 130 , a reception circuit 140 , a PRI control section 150 and a radar signal processing circuit 160 . Also, the radar device 100 may be connected to the display device 200 .

FIG. 2 is a block diagram showing the functional configuration of the radar signal processing circuit 160 of the radar device 100 according to Embodiment 1. As shown in FIG. As shown in FIG. 2, the radar signal processing circuit 160 includes a correlation processing section 161, a compensation processing section 162, a target candidate detection section 163, and a velocity/distance measurement section 164.

The radar device 100 may use the millimeter wave band or the microwave band as the operating frequency band.

A signal generation circuit 110 of the radar device 100 generates a plurality of transmission pulse signals. A mathematical model of the transmitted pulse signal is represented by T _x (h, t). Here, the argument h represents the pulse hit number (hereinafter simply referred to as "hit number"). h is an integer from 0 to H-1. H represents the number of pulse hits. The hit number h is derived from the initial letter of "hit" in English. That is, the radar apparatus 100 transmits H transmission pulse signals from 0 to H-1. The argument t represents time.

A transmission pulse signal is generated at the timing of each pulse repetition interval (hereinafter referred to as “PRI”). The design value of PRI is denoted by T _pri (h) and has units of time. Thus, the PRI may be of different lengths of time in pulses with different hit numbers. PRI is set by the PRI control unit 150 . A transmission pulse signal generated by the signal generation circuit 110 is output to the transmission/reception section 120 .

The transmission pulse signal output to transmitting/receiving section 120 is further output to antenna 130 . The antenna 130 may be a linear one called an aerial. The transmitted pulse signal emitted to the external space is reflected by the target and becomes a reflected wave signal. A mathematical model of the reflected wave signal is represented by R _x (h, t).

A reflected wave signal is received by the antenna 130 and output to the transmitting/receiving section 120 . The reflected wave signal is output to the receiving circuit 140 by the transmitting/receiving section 120 . That is, the transmitting/receiving section 120 outputs the transmission pulse signal from the signal generating circuit 110 to the antenna 130 and outputs the reflected wave signal from the antenna 130 to the receiving circuit 140 . Transmitter/receiver 120 may be realized by a circulator having three ports.

The receiving circuit 140 performs analog signal processing on the multiple input reflected wave signals to generate multiple received analog signals. A mathematical model of the received analog signal is represented by W ₀ (h,t). The receiving circuit 140 further converts the generated plurality of received analog signals into received digital signals. A mathematical model of the received digital signal is represented by V ₀ (h,t). Specifically, V ₀ (h, t) will become clear from the description below.

FIG. 3 is a block diagram showing the functional configuration of the signal generation circuit 110 of the radar device 100 according to Embodiment 1. As shown in FIG. As shown in FIG. 3, signal generation circuit 110 includes local oscillator 111 , pulse generator 112 , intrapulse modulator 113 , and output 114 .

The local oscillator 111 of the signal generation circuit 110 generates a local oscillation signal in the used frequency band. The generated local oscillation signal is output to pulse generator 112 and receiving circuit 140 .

The pulse generator 112, the intrapulse modulator 113 and the output section 114 may be of the prior art.

FIG. 4 is a flow chart showing processing steps of the radar signal processing circuit 160 of the radar device 100 according to the first embodiment. As shown in FIG. 4, the radar signal processing circuit 160 includes a step of performing correlation processing (ST161), a step of compensation processing using speed compensation candidates (ST162), a step of detecting target candidates (ST163), and a step of measuring speed and distance. and a step of processing (ST164).

The correlation processing section 161 of the radar signal processing circuit 160 modulates the reference signal and performs correlation processing for correlating the reference signal and the received digital signal (step indicated by ST161 in FIG. 3). Correlation processing section 161 performs correlation processing on a plurality of received digital signals to generate a plurality of corresponding pulse-compressed signals. In other words, the correlation processor 161 performs pulse compression. The details of the correlation processing performed by the correlation processing unit 161 will become clear from the description based on the mathematical model described later.

A mathematical model of the received digital signal is represented by _V0 . A mathematical model of the received digital signal is specifically represented by the following equation (1).

Here, m is a serial number assigned to sampling within the PRI and is an integer from 0 to M−1. Δt represents the sampling period within the PRI. In other words, mΔt represents the time from the start of sampling, but may be simply referred to as "time m" using a discrete expression. M represents the number of samplings in the PRI. h is the hit number described above.
f ₀ represents the transmission frequency. R(h, mΔt) represents the range, ie relative distance, to the target. c represents the speed of light. B ₀ represents the modulation bandwidth. T ₀ represents the transmission pulse length. A ₀ is a constant representing the amplitude.

A mathematical model of the reference signal is represented by V _ref (m). The subscript ref is the first three characters of reference, which means reference. A mathematical model of the reference signal is specifically represented by the following equation (2).

Here, ν _can (q) represents a candidate value for speed compensation (hereinafter simply referred to as "speed compensation candidate"). The subscript can is the first three characters of candidate, which means candidate. A _ref on the right side of equation (2) is the amplitude of the reference signal.

The radar apparatus 100 according to Embodiment 1 includes a Doppler frequency term in the reference signal used, as shown in Equation (2). Including the Doppler frequency term in the reference signal has the effect of suppressing Doppler coupling in correlation processing. That is, including the Doppler frequency term in the reference signal has the effect of reducing the integration loss between the received signal and the reference signal.

The speed compensation candidate is specifically represented by the following formula (3).

Here, ν _{can_cri} represents the reference value of the speed compensation candidate (hereinafter simply referred to as "speed compensation candidate reference"). The subscript cri is the first three letters of the criterion representing the criterion. q is a serial number assigned to the speed candidate (hereinafter referred to as "speed candidate number") and is an integer from 0 to Q-1. Q represents the total number of speed candidates (hereinafter simply referred to as "the number of speed candidates"). Δν _can is the step size for changing the speed candidate. The speed compensation candidate is preferably set within the speed range of the assumed target. The radar device 100 according to the technology disclosed herein can set Q, which is the number of speed candidates, and Δν _can , which is an interval for changing the speed candidates.
The terms "speed candidate" and "speed compensation candidate" may refer to the same variable, but strictly speaking, they have different meanings and should be used separately. The term "velocity candidate" is used when referring to a candidate value of velocity to be detected for a target. On the other hand, the term "speed compensation candidate" is used when referring to values used for speed compensation, which will be described later. A velocity compensation candidate is selected from the velocity candidates. In particular, the speed candidate number q assigned to the speed candidate and the speed compensation candidate number _qk assigned to the speed compensation candidate described later are used separately.
The term "target" needs to be clearly distinguished between when it is used in a dictionary sense as a general term and when it refers to a radar measurement target. Therefore, in the present specification, the term "target" is not used in the former dictionary sense, but other expressions such as "purpose" are used for distinction.

Specifically, Δν _can used in formula (3) should preferably be given by formula (4) below.

Here, Δν _amb represents the velocity interval measurable without ambiguity based on T _pri (h) (hereafter simply referred to as “ambiguity-free velocity interval”). The subscript amb is the first three letters of ambiguity, which is the English representation of ambiguity. Ambiguity means ambiguity. Also, N _{ν, amb} is a positive integer. Specifically, Δν _amb is given by the following equation (5).

By defining Δν _can in this way, signals after Fourier transform in the slow-time direction can be represented by the same sampling number, and the efficiency of pairing and detection is improved.

　Fig. 5 is a graph showing an image of the detected intensity distribution in the velocity interval without ambiguity and the velocity compensation candidate. The vertical axis of the graph shown in FIG. 5 represents intensity, and the horizontal axis represents velocity. In the graph shown in FIG. 5, plots with asterisks represent true values for the target, and plots with x marks represent target velocity candidates including velocity ambiguities.

The graph shown in FIG. 5 shows an example where the intensity is maximized at the true value of the target velocity. This phenomenon indicates that the more the velocity deviates from the true value, the more the range walk component remains after motion compensation, and the intensity of the integrated result decreases.

Δν _can shown in Equation (4) appears in the graph shown in FIG. 5 as N _ν,amb times the plot interval between adjacent asterisks or crosses. FIG. 5 shows that Δν _can adopted by the disclosed technique is wider than Δν _amb . In FIG. 5, N _ν,amb is set to 2, but N _ν,amb may be an integer larger than 2.

In the graph shown in FIG. 5, _qk represents the k-th speed compensation candidate number. In the example shown in FIG. 5, N _{ν, amb} is 2, so the speed compensation candidate numbers are q ₀ =0, q ₁ =2, q ₂ =4, . That is, unlike the speed candidate number _q , the speed compensation candidate number qk can be a discontinuous number. Since the speed compensation candidate number _qk is a number assigned in order from 0 to each speed interval without ambiguity, it is a multiple of Nv _,amb .
Also, P(q _k ) represents the intensity at q _k . The graph shown in FIG. 5 shows an example in which qk+ ₁ , which is the k+1th speed compensation candidate number, matches the true value of the target speed.

The modulation band, pulse width, and pitch of velocity compensation candidates may be determined such that the difference between P(q _k ) and P(q _k+1 ) is greater than a design value designed in advance.

Here, ΔP _des is the designed intensity difference (hereinafter referred to as “intensity difference design value”). The subscript des is the first three letters of design. ΔP _des may be an empirically obtained value such as 3 [db]. In this way, the intensity difference design value may be used as a reference for deciding which value to set for Nv _{, amb} , that is, how to set the interval between speed compensation candidates.

Specifically, the correlation processing performed by the correlation processing unit 161 may be based on the following formula processing.

Here, M _P appearing in the summation interval on the right side of equation (7) represents the number of sampling points in the pulse. Also, the overscore appearing on the right side of equation (7) represents the operation of complex conjugation. That is, the overlined V _ref (p) is the complex conjugate of V _ref (p). Equation (7) is a discrete-time convolution operation used for a typical correlation operation, but there are various styles of correlation operation. The radar signal processing circuit 160 according to the technique of the present disclosure may use another known style of correlation calculation instead of Equation (7). A pulse-compressed signal (hereinafter referred to as a “pulse-compressed signal”) is expressed as F _v0vref (h, m) on the left side of Equation (7).

A compensation processing unit 162 of the radar signal processing circuit 160 performs motion compensation processing on the pulse compression signal. As shown in FIG. 1, the radar device 100 according to the technology of the present disclosure is assumed to be a monostatic radar using an antenna 130 for both transmission and reception. In the case of monostatic radar, the receive gate cannot be opened during pulse transmission, resulting in a so-called blind region due to lack of data in the received signal. The motion compensation processing performed by the compensation processing unit 162 is to interpolate the blind region information from the received signal information of adjacent pulses on the time axis. A pulse-compressed signal that has undergone motion compensation processing is referred to herein as a motion compensation candidate.

A compensation processing unit 162 of the radar signal processing circuit 160 performs Fourier transform on the pulse-compressed signal subjected to velocity compensation processing.

Here, K in the script typeface on the left side of equation (8) represents an operation for performing speed compensation processing on the contents of the square brackets. In addition, the script typeface F on the left side of equation (8) represents the operation of Fourier transforming the contents of the square brackets. Motion compensation is a combination of velocity compensation and Fourier transform.
The function argument k appearing on the right side of Equation (8) is a serial number assigned to the spectrum obtained by performing the discrete Fourier transform. The details of formula (8) will become clear from the description below.

In the compensation processing performed by the compensation processing unit 162, it is preferable to determine in advance which velocity candidate is used for compensation. For example, the compensation process may be determined in advance to compensate with v _can (q) of the velocity compensation candidate whose velocity candidate number is q.

FIG. 6 is a graph representing an assumed velocity interval of a target, an ambiguity-free velocity interval, and an image of a target candidate.
In general, when PRF (Pulse Repetition Frequency), which is the reciprocal of PRI, is lowered for reasons such as long-distance observation, a velocity interval in which a so-called virtual image due to ambiguity does not appear (“velocity interval without ambiguity”) ) is narrower.
Also, in general, when the target is moving at high speed, it is necessary to take a wide speed interval. In order to find the target speed with high accuracy, the radar according to the conventional technology must select a large number of speed candidates and perform a speed search.
FIG. 6 represents a situation in which the target assumed speed interval is wide and the PRI is small. Also, FIG. 6 shows an example in which the intervals of speed compensation candidates are aligned with the interval of speeds that can be solved without ambiguity (this is also the same as the “speed interval without ambiguity”). FIG. 6 also shows that the velocity search must select the most probable value for the target from among the many candidates generated by the velocity ambiguity.

Using the velocity compensation candidate ν _can , the compensation distance and compensation signal can be calculated based on the following mathematical model.

Here, R _can (h) on the left side of Equation (9) represents the compensation distance. The alphabet R used is the initial letter of Range, which is an English notation for range, which means distance. Argument h is the aforementioned hit number. The mathematical model shown in Equation (9) simply expresses the relationship between velocity, time and distance. The reason why the minus sign is used on the right side of the equation (9) is that the speed axis and the distance axis are defined so that their directions are opposite to each other.

Here, V _RCAN (h) on the left side of equation (10) represents the compensation signal created from the compensation distance. Although the right side of Equation (10) does not indicate the amplitude, the mathematical model for the compensation signal may be such that the right side of Equation (10) is multiplied by a constant representing the amplitude.

By using the results of equations (7) and (10), a velocity-compensated signal (hereinafter simply referred to as "velocity-compensated signal") is derived.

Equation (11) details the speed compensation portion of Equation (8).
Here, the subscript range of the script typeface F represents the operation of performing the Fourier transform in the distance direction on the contents of the square brackets. A Fourier transform in the range direction means a transformation from the fast-time domain to the fast-time frequency domain. The inverse Fourier transform in the range direction means the inverse transform, ie from the fast-time frequency domain to the fast-time domain.

By Fourier transforming the result obtained by the equation (11), that is, the left side of the equation (11) in the slow time direction, the signal after the motion compensation processing (hereinafter simply referred to as the "signal after the motion compensation") is obtained as follows: be guided.

Equation (12) details the Fourier transform portion of Equation (8). Equation (12) is no different from what represents the general discrete Fourier transform. As indicated by the right side of Equation (12), the variable k is the sampling number when performing the discrete Fourier transform. The example of equation (12) shows that from one sampling to the next, i.e., for each increment of h, the discrete Fourier transform with the fundamental wave advances in phase by 2πk divided by K. ing. The exp term on the right-hand side of equation (12) corresponding to the fundamental wave represents a point obtained by equally dividing the unit circle on the complex plane, and is therefore sometimes called a rotator.

The above is a general pulse Doppler technique with velocity compensation processing added, but the technique of the present disclosure is not limited to this. The radar device 100 according to the technology disclosed herein may perform another process with a similar purpose.

The target candidate detection unit 163 of the radar signal processing circuit 160 calculates the relative distance and relative speed of the target candidate (step ST163 in FIG. 4).
The target candidate detection unit 163 may detect target candidates using an algorithm such as CA-CFAR (Cell Average-Constant False Alarm Rate).
CA-CFAR can maximize the detection probability such that the false alarm probability is a constant value. That is, CA-CFAR has the characteristic of being able to control erroneous detection and detect target candidates based on signal strength while minimizing noise detection.

As shown in FIG. 4, the radar signal processing circuit 160 repeats the processing steps of ST161, ST162, and ST163 by the number of speed candidates.

Through the above process, target candidate detection results for the number of speed candidates are obtained, and the detection performance can be further improved by performing incoherent integration on each of them. FIG. 7 is a graph in which peak intensities of speed candidates are arranged. The horizontal axis represents speed and the vertical axis represents distance. If velocity candidates are set as integral multiples of velocities that can be unambiguously solved, integration is performed in the same velocity bin, so the peak intensities are equal in the velocity direction and aligned at distance intervals corresponding to the velocity candidates in the distance direction. Assuming that the speed interval of the speed candidates is Δν, the distance interval Δr corresponding to the speed candidate is expressed by the following equation.

Incoherent integration of multiple velocity candidate peak intensities is possible by shifting the distance of each peak intensity using equation (13). Here, the motion-compensated signal after the distance direction shift is represented by the following equation.

However, r_shift represents the process of distance-shifting the motion-compensated signal (F _FFT ) by the product of the speed candidate number and the distance interval (Δr).

Also, the incoherent integration of the peak intensity of multiple velocity candidates is expressed by the following equation.

Here, the subscript IC attached to the variables is derived from the English notation of incoherent. Note that the expression (15) uses the summation symbol instead of the integral symbol, but this merely indicates that the integration is performed discretely.

Radar device 100 according to the technology of the present disclosure improves detection performance by using F _{FFT_IC} (k, m) obtained by incoherent integration instead of using each of F′ _FFT (k, m). There is an effect that it can be made.

The speed measurement/distance measurement unit 164 of the radar signal processing circuit 160 calculates the peak intensity of each of the speed candidates, and calculates the peak intensity corresponding to each of the speed compensation candidates. Velocity measurement/distance measurement unit 164 also calculates a plausible estimated value of the speed of the target from the information on the peak with the maximum intensity (step indicated by ST164 in FIG. 4).

FIG. 8 is a graph showing an image of calculating an estimated target speed from the peak intensity of each speed compensation candidate. The horizontal axis of the graph in FIG. 8 represents the value of the speed compensation candidate, and the vertical axis of the graph represents the intensity. FIG. 8 shows that the strength is greatest when the value of the velocity compensation candidate is closest to the true value of the target velocity. Being able to estimate a target velocity close to the true value means that the velocity ambiguity is resolved and the integration efficiency of the target velocity within the PRF of the range of velocity candidates is not degraded, i.e. improved. .
FIG. 8 also shows that the target velocity can be estimated from the trend of the plot using discrete velocity compensation candidates wider than the velocity ambiguity interval. In FIG. 8, the plot shows a linear trend, ie, a linear decrease in intensity as the velocity estimate deviates from the true value. However, even if the plot is not necessarily approximated by two straight lines, it is possible to estimate a plausible value.

p(0) _, . _. . , p(q _k ), p( _{q k+1} ) _, . , …, ). In the example shown in FIG. 8, the graph monotonically increases on the left and monotonically decreases on the right. More specifically, the graph monotonically increases up to p(q _k ) and monotonically decreases after p(q _k ). Thus, in the example of FIG. 8, it can be inferred that the intensity is maximized at velocities between q _k and q _k+1 .

In this way, when the intensity is plotted for each speed compensation candidate, the plot changes from an increasing trend to a decreasing trend at a certain speed compensation candidate number. The disclosed technique divides the first half group of plots that are on the increase and the second half group of the plots that are on the decrease, and mathematically models each of them. Although the mathematical model shown in FIG. 8 uses linear approximation based on the method of least squares, it is not limited to this. The mathematical model may be a higher dimensional curve approximation or may be based on other interpolation methods. Then, the target speed can be obtained as an intersection point between the curve, etc., which is the mathematical model of the first half group and the curve, etc., which is the mathematical model of the second half group.

An estimate of the target's velocity, determined as the intersection of the two mathematical models, can be expressed as follows.

Here, ν _res on the left side of Equation (16) is the target speed estimation result. The subscript res is the first three characters of result which means the result. The dashed ν in the first term on the right side of equation (16) is the strongest of the velocity compensation candidates. The dashed ν plot in FIG. 9 is referred to as the “nearest velocity plot”. dν _res in the second term on the right side of Equation (16) represents the velocity difference value obtained from the position of the intersection of the two mathematical models.
That is, the radar device 100 according to the technique of the present disclosure divides the velocity candidates into a first half group that tends to increase and a second half group that tends to decrease, based on the detection strength of each of the speed candidates. Approximate straight lines or curved lines are determined based on the method of least squares, respectively, and the speed of the target is determined as the point of intersection of the respective approximate straight lines or curved lines.

FIG. 9 is a graph showing an image of calculating the estimated distance from the estimated speed of the target. As shown in the lower graph of FIG. 9, the estimated distance is obtained from the relational expression between distance and speed.

Here, Δr _can on the left side of equation (17) is the step size of the distance candidate corresponding to Δν _can , which is the step size of the speed candidate.
From equations (16) and (17), the target range estimate is obtained as follows.

Here, r _res on the left side of equation (18) is the target range estimation result. The dashed r in the first right-hand side of Eq. (18) is the distance corresponding to the dashed first v in the right-hand side of Eq. (16), i.e. the nearest velocity plot. be.

Generally, there is a method of obtaining the maximum value and the minimum value from a derivative function. That is, the slope at the extremum is 0, and this property can be applied to find the velocity candidate with the highest strength in the technique of the present disclosure. The velocity candidate with the highest intensity can be found by finding the difference in intensity between adjacent velocity candidates as follows.

For _example , when it is found that there is a maximum value of intensity between the _{qk- th} velocity compensation candidate and the qk _+1-th velocity law phase candidate as illustrated in FIG. It is also possible to change the compensation candidates in finer increments and obtain the speed at which the intensity is maximized based on equation (19).
That is, the radar apparatus 100 according to Embodiment 1 selects the maximum intensity and the second maximum intensity from the detection results of the velocity compensation candidates, and estimates the velocity of the target.

The target velocity may be estimated using a discricurve. FIG. 10 is an image diagram showing the relationship between the ratio of sum signal to difference signal with respect to signal intensity and speed. The curves in FIG. 10 are discricurves prepared in advance. Here, the sum signal and the difference signal regarding signal intensity are obtained as follows.

Here, p _Σ is the sum signal of the signal intensities, and p _Δ is the difference signal of the signal intensities.
The horizontal axis of the discricurve shown in FIG. 10 is velocity. Also, the vertical axis of the discricurve shown in FIG. 10 is the ratio of the sum signal to the difference signal with respect to the signal intensity, which is calculated as follows.

FIG. 10 shows the result of estimating the speed of the target, ν _res It shows that it is possible to obtain

FIG. 11 is a diagram showing an example of the hardware configuration of the signal processing circuit 170 of the radar device 100 according to the technology disclosed herein. Here, the signal processing circuit 170 is hardware that realizes the PRI control unit 150 and the radar signal processing circuit 160 that are the functional configuration of the radar device 100 . The signal processing circuit 170, even if it is dedicated hardware, is also called a CPU (Central Processing Unit, processing unit, arithmetic unit, microprocessor, microprocessor, processor, DSP) that executes programs stored in memory. may be called). Note that FIG. 11 illustrates a case where the signal processing circuit 170 is realized by a CPU that executes a program stored in a memory. Signal processing circuit 170 includes processor 171 , memory 172 , storage device 173 , input/output interface 174 , and signal path 175 . The signal processing circuit 170 receives information from the receiving circuit 140 and is connected to the external display device 200 . Here, the term "processor" is used as a general noun, and the term processor 171, which is a component of the signal processing circuit 170, is used as a proper noun to distinguish between the two. The term "memory" is used as a general noun, and the memory 172, which is a component of the signal processing circuit 170, is used as a proper noun to distinguish between them.

Where signal processing circuitry 170 is dedicated hardware, signal processing circuitry 170 may be, for example, a single circuit, a decoding circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof. do. The functions of the PRI control unit 150 and the radar signal processing circuit 160 may be realized by separate processing circuits, respectively, or may be collectively realized by one processing circuit.

When the signal processing circuit 170 is configured by a CPU, the functions of the PRI control unit 150 and the radar signal processing circuit 160 are realized by software, firmware, or a combination of software and firmware. Both software and firmware are written as programs and stored in memory. The signal processing circuit 170 realizes the function of each part by reading out and executing the program stored in the memory. That is, when the function is executed by the signal processing circuit 170, the radar apparatus 100 performs a process of setting a PRI, a step of performing a correlation process (ST161), a step of a compensation process using a speed compensation candidate (ST162), and a target A memory is provided for storing a program for executing the candidate detection step (ST163) and the speed measurement/distance measurement step (ST164). It can also be said that these programs cause a computer to execute the procedures and methods of the PRI control unit 150 and the radar signal processing circuit 160 .

The processor 171 that executes the program may be composed of, for example, an LSI.

Here, the memory may be, for example, non-volatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, EEPROM. Furthermore, the memory may be a magnetic disk, flexible disk, compact disk, mini disk, DVD, or the like. The memory may be in the form of HDD, SSD, and the like.
FIG. 11 includes memory 172 and storage 173 to illustrate that memory can take many forms. The memory 172 and storage device 173 are a program memory for storing various program codes to be executed by the processor 171, a work memory used when the processor 171 executes digital signal processing, and a memory used for digital signal processing. and a temporary storage memory in which the data to be processed is stored.

It should be noted that the functions of the PRI control unit 150 and the radar signal processing circuit 160 may be partially realized by dedicated hardware and partially realized by software or firmware. For example, the function of the PRI control unit 150 is realized by a processing circuit as dedicated hardware, and the function of the radar signal processing circuit 160 is realized by reading and executing a program stored in the memory by the processing circuit. is also possible.

Thus, the signal processing circuit 170 can implement the functions of the PRI control section 150 and the radar signal processing circuit 160 by hardware, software, firmware, or a combination thereof.

Since the radar device 100 according to Embodiment 1 has the above configuration, it is possible to estimate the speed of the target based on a plurality of speed candidates within a wide range in which speed ambiguity appears. Due to this effect, the radar device 100 according to the first embodiment can estimate the distance and speed of the target with a smaller amount of calculation than in the conventional art and without being affected by the speed ambiguity.

Embodiment 2.
The radar apparatus 100 according to the second embodiment includes a radar signal processing circuit 160 (160B) having a configuration different from that of the radar signal processing circuit 160 according to the first embodiment. In the second embodiment, unless otherwise specified, the same reference numerals as in the first embodiment are used, and overlapping descriptions are omitted as appropriate.

FIG. 12 is a block diagram showing the functional configuration of the radar signal processing circuit 160 (160B) of the radar device 100 according to the second embodiment. As shown in FIG. 12, radar signal processing circuit 160 (160B) includes CZT pulse Doppler processing section 165 instead of correlation processing section 161 and compensation processing section 162 . As shown in FIG. 12, the CZT pulse Doppler processing unit 165 is provided at the foremost stage in the radar signal processing circuit 160 (160B), followed by the target candidate detection unit 163, and further after the speed measurement/distance measurement unit 164. is provided. CZT is an acronym for Chirp Z-Transform and means Chirp z-transform.

The chirp z-transform is an FFT algorithm proposed by Bluestein in 1968, and is also called Bluestein's FFT algorithm. The chirp z-transform has the characteristic that it can fast Fourier transform any length of discrete data.

FIG. 13 is a flow chart showing processing steps of the radar signal processing circuit 160 (160B) of the radar device 100 according to the second embodiment. As shown in FIG. 13, the processing steps of radar signal processing circuit 160 (160B) include a CZT pulse Doppler processing step (ST165) performed by CZT pulse Doppler processing section 165 and a target candidate detection step (ST163) performed by target candidate detection section 163. ), and a speed measurement/distance measurement step (ST164) performed by the speed measurement/distance measurement unit 164 .

The radar signal processing circuit 160 (160B) according to Embodiment 2 performs correlation processing and velocity compensation using chirp z-transform. Specifically, the CZT pulse Doppler processing unit 165 of the radar signal processing circuit 160 (160B) performs CZT processing in the hit direction in consideration of velocity compensation on the received digital signal shown in Equation (1), and further performs correlation processing. (step indicated by ST165 in FIG. 13).

FIG. 14 is a flowchart showing details of the CZT pulse Doppler processing step (ST165) in the flowchart shown in FIG. As shown in FIG. 14, the CZT pulse Doppler processing step (ST165) includes an FFT processing step in the range direction (ST165A), a CZT processing step in the hit direction (ST165B), and a processing step of multiplying by a reference function (ST165C). and an IFFT processing step (ST165D) in the distance direction.

The CZT pulse Doppler processing unit 165 executes FFT processing in the distance direction exemplified by the following formula on the received digital signal (step indicated by ST165A in FIG. 14).

Here, _mp is the sampling number in one PRI. M _p is the total number of samplings in one PRI. M _fft is the total number of Fourier transform points. _kr is a serial number attached to the result of FFT in the range direction. In other words, _kr is the bin number attached to the fast-time frequency spectrum. The details of the bin numbers will become clear from the description below.

The CZT pulse Doppler processing unit 165 executes CZT processing in the hit direction exemplified by the following formula (step indicated by ST165B in FIG. 14).

Here, the subscript CZT of the script typeface F represents the operation of performing chirp z-conversion in the hit direction on the contents of the square brackets. The hit direction can be imagined as the direction in which the hit number increases or decreases, and is synonymous with the distance direction or range direction. This can also be understood from the fact that equation (23) is a process performed on the result of FFT in the range direction of equation (22). In other words, the radar apparatus 100 according to Embodiment 2 transforms the fast-time direction of the received signal into the frequency domain and uses chirp z-transform.
h _czt represents the Doppler velocity bin number of the signal after CZT processing. The bin number is a serial number given to the FFT bins. FFT bins or bins are derived from the English word bin, and since the frequency spectrum is arranged like a strip, the term is used to refer to the strip shape. H _czt is the total number of bins obtained after CZT treatment. k _r may be referred to as the range bin number, in contrast to h _czt being the Doppler velocity bin number.

The rotator term on the right side of equation (21) is specifically defined as follows.

where A _kr on the left side of equation (24) is the rotator associated with the starting phase of the transform corresponding to k _r . f _kr is the fast-time frequency of the spectrum located at k _r . ν _st is the rate of conversion initiation. The subscript st of ν _st is the first two characters of start, which means the start.
W _kr (h _czt ) on the left side of Equation (25) is the rotator related to the phase change width of the transform corresponding to k _r . Δν _czt is the variation width of the velocity.
In other words, in the radar apparatus 100 according to Embodiment 2, the compensation processing unit 162 performs phase compensation using chirp z-transform, and performs the motion compensation with the motion compensation candidate based on the preset velocity.

There is no difference in that both the processing shown in formula (22) and the processing shown in formula (23) are FFTs. The FFT shown in Equation (22) is the first FFT and is sometimes called Range-FFT. The FFT shown in Equation (23) is the second FFT for the result of the first FFT, and is also called Doppler-FFT. In general, by performing two FFTs, Range-FFT and Doppler-FFT, it is possible to measure the velocity of each of multiple objects at the same distance.

The relative velocity sought by CZT processing appears in equations (24) and (25). Specifically, the relative velocity is a value according to the following formula.

ν _czt (h _czt ) on the left side of equation (26) represents the relative velocity when the Doppler velocity bin number is h _czt .

Δν _czt used in equation (25) has the following relationship with H _czt .

where ν _en is the rate of conversion completion. The subscript en of ν _en is the first two characters of end, which means the end. Equation (27) simply states that the step size is found by dividing the total width of the velocity by the number of sampling points.

ν _st and ν _en used in equation (27) have the following relationship with ν _can .

where _kv is a constant. d _v represents the velocity resolution, ie the smallest possible velocity step size. _dv can be shown as follows if it expresses with a numerical formula.

Fourier transform is also performed on the reference signal in the same manner as in the processing on the received digital signal described above. The reference signal used in Embodiment 2 has the same structure as the reference signal in Embodiment 1 shown in Equation (2), but the details are shown below.

In this way, the reference signal shown in Equation (30) uses the relative velocity shown in Equation (26).

A Fourier transform performed on the reference signal is, for example, as follows.

Note that the Fourier transform shown in Equation (31) is the same as that shown in Equation (22).

CZT pulse Doppler processing section 165 performs a process of multiplying the respective Fourier-transformed received digital signals by a reference function (step ST165C in FIG. 14).

CZT pulse Doppler processing section 165 performs inverse Fourier transform in the distance direction on the result of multiplying the two signals shown in equation (32) (step ST165D in FIG. 14).

R _pc (h _czt , l) obtained by Equation (33) is a signal that has undergone correlation processing and compensation processing. R _pc (h _czt , l) is equivalent to F _FFT (k, m) shown in equation (12) in the first embodiment. Therefore, the subsequent processing may be performed as described in the first embodiment.

As described above, since the radar apparatus 100 according to the second embodiment has the above configuration, in addition to the effects shown in the first embodiment, the integration loss due to Doppler coupling is reduced, and the distance shift due to Doppler coupling is reduced. It has the effect of making it smaller.

Note that the hardware of the radar device 100 according to the second embodiment may be implemented with the same configuration as that of the first embodiment.

Embodiment 3.
The radar device 100 according to the third embodiment is based on the configuration of the radar device 100 according to the second embodiment, and includes a radar signal processing circuit 160 (160C) with a certain function added. The radar device 100 according to Embodiment 3 has a configuration that is particularly effective when the radar device 100 employs a staggered PRI method in which PRIs are set at unequal intervals between pulses. The term "stagger" is derived from the English staggered. Staggered originally meant "staggered" or "staggered", but in this technical field it means uneven spacing.
Embodiment 3 uses the same reference numerals as those of the above-described embodiments, unless otherwise specified, and overlapping descriptions are omitted as appropriate.

FIG. 15 is a block diagram showing the functional configuration of the radar signal processing circuit 160 (160C) of the radar device 100 according to the third embodiment. As shown in FIG. 15, the radar signal processing circuit 160 (160C) includes an averaging section 166 in addition to a CZT pulse Doppler processing section 165, a target candidate detection section 163, a velocity/distance measurement section 164, and so on.

The staggered PRI scheme (simply called "staggered scheme") is an effective means of resolving Doppler and range ambiguities. In the staggered method, the pulse repetition period changes for each hit number. Therefore, in Embodiment 3, the pulse repetition periods are expressed as T _PRI (0), T _PRI (1), . . . , _{T PRI (} h), .

PRI control section ₁₅₀ according to Embodiment 3 has a pulse width of T ₀ and pulse repetition periods of T _PRI (0), T _PRI (1), . . . , T _PRI (h), . H-1) to generate a timing signal for generating a series of signals. The generated timing signal is sent to signal generation circuit 110 .
A series of signals employed by the radar apparatus 100 according to Embodiment 3 may be created based on the concept of the reference period. In other words, a series of signals may be obtained by linearly increasing or decreasing the period starting from the reference period, for example.

FIG. 16 is a flow chart showing processing steps of the radar signal processing circuit 160 (160C) of the radar device 100 according to the third embodiment. As shown in FIG. 16, the processing flow of the radar signal processing circuit 160 (160C) has double processing loops, an inner processing loop for velocity candidates and an outer processing loop for pulse repetition periods. The inner processing loop for speed candidates is the same as the processing loop for speed candidates in the flowchart shown in FIG.

In this way, the radar signal processing circuit 160 (160C) of the radar device 100 according to the third embodiment has pulse repetition periods of T _PRI (0), T _PRI (1), ..., T _PRI (h), ..., T _PRI (H-1), an estimate of the target's range and velocity is calculated. The reason why the radar signal processing circuit 160 (160C) includes the averaging unit 166 is to calculate a more probable estimated value by averaging the estimated values calculated in each pulse repetition cycle. Averaging section 166 calculates the average value of the estimated values calculated in each pulse repetition period (step ST166 in FIG. 16).

FIG. 17 is the image diagram shown in FIG. 8 applied to the third embodiment. FIG. 18 is the image diagram shown in FIG. 9 applied to the third embodiment.

As described above, since the radar device 100 according to Embodiment 3 has the above configuration, in addition to the effects shown in Embodiment 2, the staggered PRI method can be adopted, and the estimated value calculated at each pulse repetition period By taking the average of , it is possible to calculate a more probable estimated value.

Note that the hardware of the radar device 100 according to the third embodiment may be implemented with the same configuration as that of the first embodiment.

Embodiment 4.
The radar apparatus 100 according to the fourth embodiment is based on the configuration of the radar apparatus 100 according to the first embodiment, and includes a radar signal processing circuit 160 in which the correlation processing unit 161 and the compensation processing unit 162 are replaced with an inter-pulse stagger integration unit 167. (160D). The radar device 100 according to Embodiment 4 has a configuration that is particularly effective when the radar device 100 employs the staggered PRI method. In the fourth embodiment, unless otherwise specified, the same reference numerals as in the previous embodiments are used, and duplicate descriptions are omitted as appropriate.

The staggered method assumed in the fourth embodiment is a special method in which several PRI pulses with the same interval are consecutively shot to form a group. This is a staggered method in which a plurality of groups exist and different groups have different PRIs. For example, assume that four pulses of PRI with the same interval form a group. In this case, T _PRI (0) to T _PRI (3) constitute the first group and have the same value. T _PRI (4) to T _PRI (7) constitute the second group, which is another common value different from the first group. Subsequent groups are similarly grouped, and in the case of this example, one series is assumed to have a number of groups obtained by dividing H by 4. After the first series of signal irradiation is performed, the hit number returns to 0 and the second series of signal irradiation is performed. In the second series as well, T _PRI (0) to T _PRI (3) constitute the first group, and T _PRI (4) to T _PRI (7) constitute the second group. The radar device 100 according to the fourth embodiment repeats pulse irradiation in this manner.

The PRI control unit 150 according to the fourth embodiment generates timing signals for generating staggered signals that form the above groups. The generated timing signal is sent to signal generation circuit 110 .

FIG. 20 is a flow chart showing processing steps of the radar signal processing circuit 160 (160D) of the radar device 100 according to the fourth embodiment. As shown in FIG. 20, the processing steps of the radar signal processing circuit 160 (160D) include the inter-pulse stagger integration step (ST167) performed by the inter-pulse stagger integration unit 167 and the target candidate detection step (ST167) performed by the target candidate detection unit 163. ST163) and a speed measurement/distance measurement step (ST164) performed by the speed measurement/distance measurement unit 164.

It is conceivable to improve the SN ratio by successively adding and integrating reflected signals of PRIs with the same interval. The reason why the radar signal processing circuit 160 (160D) according to the fourth embodiment includes the pulse-to-pulse stagger integration unit 167 is to achieve this effect.

FIG. 21 is a reference diagram showing an image of integration performed by the pulse-to-pulse stagger integration unit 167 according to the fourth embodiment. More specifically, FIG. 21 represents the PRI for each hit by describing the number of the group to which the PRI belongs. The right direction in FIG. 21 is the direction in which the hit number increases. FIG. 21 exemplifies a case where four pulses of PRI with the same interval continue to form a group. Also, FIG. 21 exemplifies a case where H is 16 and the number of groups is 4. In FIG. The downward direction in FIG. 21 represents the direction in which the number of series increases.

The pulse-to-pulse stagger integration unit 167 according to the fourth embodiment performs coherent integration on a plurality of series of reflected signals shown in the reference diagram of FIG. 21, for example. The pulse-to-pulse stagger integrator 167 first performs coherent integration on reflected signals of PRIs with the same interval, and then coherently integrates reflected signals of PRIs with different intervals (step ST167 in FIG. 19). The coherent integration performed by the pulse-to-pulse stagger integration unit 167 may be the above-described CZT or discrete Fourier transform of another style. Coherent integration may be enhanced by using a projection matrix or by applying a filter.

Coherent integration of reflected signals with the same PRI interval may be performed on reflected signals belonging to the same group in the same series (see “integration direction 1” in FIG. 21), or may be performed on reflections of the same group number in different series. It may be done for the signal (see "integration direction 2" in FIG. 21).

The radar apparatus 100 according to Embodiment 4 performs coherent integration on signals for each pulse included in the pulse repetition period of the same type, and then performs coherent integration in the pulse repetition period of a different type. to detect the target.

The radar apparatus 100 according to Embodiment 4 includes a pulse-to-pulse stagger integration section 167, and improves the SN ratio by post-detection integration.
It is believed that SNR improvement can also be achieved by pre-detection integration. The radar device 100 according to the technology disclosed herein may use a filter such as a matched filter to improve the SN ratio.

As described above, since the radar apparatus 100 according to the fourth embodiment has the above configuration, in addition to the effects shown in the second embodiment, post-detection integration is performed for reflected signals with PRIs having the same interval, so the SN ratio can be improved. Post-detection integration is expected to have the same effect as the averaging shown in the third embodiment. Therefore, it can be said that the radar device 100 according to Embodiment 4 has the effect of being able to calculate a more probable estimated value.

The radar device 100 according to the technology disclosed herein can be used as a measuring device that measures the distance and speed of a target, and has industrial applicability.

100 radar device, 110 signal generation circuit, 111 local oscillator, 112 pulse generator, 113 intra-pulse modulator, 114 output section, 120 transmission/reception section, 130 antenna, 140 reception circuit, 150 PRI control section, 160, (160B), (160C), (160D) Radar signal processing circuit, 161 correlation processing unit, 162 compensation processing unit, 163 target candidate detection unit, 164 speed and distance measurement unit, 165 CZT pulse Doppler processing unit, 166 averaging unit, 167 pulse Inter-stagger integrator, 170 signal processing circuit, 171 processor, 172 memory, 173 storage device, 174 input/output interface, 175 signal path, 200 display.

Claims (14)

1. a PRI controller that sets a predetermined pulse repetition period for each hit;
   a signal generation circuit that continuously generates a plurality of transmission pulse signals at timing based on the pulse repetition period;
   a transmission/reception unit that transmits the transmission pulse signal to an external space and receives a plurality of reflected wave signals corresponding to each of the transmission pulse signals from the external space;
   a receiving circuit for generating a plurality of received signals respectively corresponding to the transmitted pulse signals by sampling each of the reflected wave signals received by the transmitting/receiving unit;
   a correlation processing unit that pulse-compresses the received signal by correlation calculation;
   a compensation processing unit that performs motion compensation with a motion compensation candidate based on a preset speed;
   a target candidate detection unit that detects a target candidate based on the signal processed by the compensation processing unit;
   velocimetry for estimating the unambiguous velocity and distance of a target from results from the target candidate detector processed using a plurality of the motion compensation candidates at intervals wider than the unambiguously measurable velocity interval; A radar device comprising a distance measuring unit.
2. 2. The radar apparatus according to claim 1, wherein the motion compensation candidate interval is an integral multiple of the velocity interval.
3. 2. The radar apparatus according to claim 1, wherein the motion compensation candidate interval is calculated based on the integrated loss of the target in the target candidate detection unit.
4. 2. The radar system according to claim 1, wherein signals generated by said motion compensation candidates are incoherently integrated.
5. The target candidate detection unit is
   2. The radar system according to claim 1, wherein the relative distance and relative velocity of said target candidate are calculated.
6. 2. The radar apparatus according to claim 1, wherein the number of velocity candidates required for performing said motion compensation and the step size of said velocity candidates are configurable.
7. dividing the speed candidates into a first half group that tends to increase and a second half group that tends to decrease based on the detection strength of each of the speed candidates;
   Obtaining an approximate straight line or approximate curve based on the least squares method for each of the first half group and the second half group,
   2. The radar device according to claim 1, wherein the velocity of said target is obtained as an intersection point where said approximated straight lines or said approximated curves intersect.
8. 2. The radar device according to claim 1, wherein the maximum intensity and the second maximum intensity are selected from the detection results of the velocity compensation candidates, and the velocity of the target is estimated.
9. 8. The radar apparatus according to claim 7, wherein the speed compensation candidate number is selected when the difference value before and after is the smallest from the detection results of the speed compensation candidates.
10. 8. The radar apparatus according to claim 7, wherein the speed of the target is estimated based on the sum and difference of two signal intensities selected from results of processing speed compensation candidates.
11. 2. The radar apparatus according to claim 1, further comprising an averaging unit that calculates an average value of estimated values calculated respectively according to the type of the pulse repetition period.
12. 2. The target is detected by performing coherent integration on signals for each pulse contained in the pulse repetition period of the same type, followed by coherent integration in the pulse repetition period of a different type. The radar device as described.
13. 2. The radar apparatus according to claim 1, wherein said compensation processing unit performs phase compensation using a chirp z-transform, and performs said motion compensation with said motion compensation candidate based on a preset speed.
14. 14. The radar apparatus according to claim 13, wherein the fast-time direction is transformed into the frequency domain for the received signal and the chirp z-transform is used.

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