JP2013113723A - Radar system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a radar system capable of improving range-finding performance and distance resolution and coping with targets of a plurality of targets.SOLUTION: The radar system includes a transmitter 2 for setting a parameter provided with a first condition having a relative speed and a relative distance within a range with a target set in advance to solve ambiguity of a distance in PRI of the target having the relative speed, and a second condition in which distance resolution in the PRI of the target having the relative distance has higher accuracy than distance resolution after FM ranging, and radiating a transmission signal subjected to intrapulse modulation by PRI to a carrier signal frequency-modulated over a plurality PRIs on the basis of the set parameter.

Description

  The present invention relates to a radar apparatus that eliminates distance ambiguity and accurately measures a target distance.

A conventional technique for measuring a distance without ambiguity when there is a distance ambiguity within a PRI (Pulse Repetition Interval) will be described by taking the radar apparatus disclosed in Non-Patent Document 1 as an example.
In a conventional radar apparatus having a distance ambiguity in the PRI, as shown in FIG. 15, a transmission signal having a constant frequency for calculating a Doppler frequency (speed) within 1 CPI (Coherent Processing Interval). Ranging is performed by a pulse Doppler process using, and an FM (Frequency Modulation) ranging method using a transmission signal subjected to frequency modulation over a plurality of PRIs for obtaining a beat frequency including distance information and speed information. Since the beat frequency obtained by FM ranging includes speed and distance information, the distance information is calculated from the beat frequency using speed information obtained in advance by pulse Doppler processing. Thus, by performing pulse Doppler processing and FM ranging, it is possible to calculate the relative distance to the target even when there is a distance ambiguity in the PRI, and it is expected to improve the ranging performance.

Guy Morris, “AIRBORNE PULSED DOPPLER RADAR second edition,” Artech House, pp. 95-98, 1996.

  The conventional radar apparatus represented by Non-Patent Document 1 requires two processes, a pulse Doppler process and an FM ranging process that performs frequency modulation, and divides 1 CPI into two, thereby reducing the observation time for one process. There was a problem that the detection performance deteriorated. In addition, as shown in FIG. 16, when dealing with a plurality of targets is assumed, the conventional radar apparatus has a frequency modulation different from that of the pulse Doppler processing in order to solve the combination of the speed and the beat frequency by FM ranging by the pulse Doppler processing. Two FM rangings, that is, three processes are required, and 1CPI is divided into three, so that the detection performance is further deteriorated. Furthermore, in order to improve the distance resolution, it is necessary to widen the frequency modulation bandwidth of FM ranging. However, since the distance that can be calculated without ambiguity is reduced in proportion to the distance resolution, the distance resolution is increased. There was a problem that there was a limit.

  The present invention has been made to solve the above-described problems. In the case where a distance ambiguity exists in the PRI, the present invention aims to improve detection performance, distance measurement performance and distance resolution, and cope with multiple targets. It is an object to obtain a radar device that enables this.

  In the radar apparatus according to the present invention, the target has a relative speed and a relative distance within a preset range, the first condition for solving the ambiguity of the PRI internal distance of the target having the relative speed, and the target having the relative distance. A parameter having a second condition in which the distance resolution in the PRI is higher than the distance resolution after FM ranging is set, and a carrier signal frequency-modulated over a plurality of PRIs based on the set parameter A transmitter that radiates a transmission signal modulated in the pulse by PRI and a transmission signal reflected back by the target as a reception signal, and a carrier signal obtained from the transmitter is received with respect to the reception signal. FM conversion is performed on the received beat signal obtained from the receiver and the received beat signal obtained from the receiver by down-converting the received beat signal. Distance in PRI for calculating distance-Distance in PRI for creating distance map after FM ranging-Distance map creating unit after FM ranging and Distance in PRI-Distance map creating unit after FM ranging The target candidate detection unit that detects the target candidate based on the signal strength and the distance after the FM ranging of the target candidate obtained from the target candidate detection unit with respect to the distance map after the FM-distance range in the PRI, A target relative distance calculation unit that eliminates the distance ambiguity of the distance in the PRI and calculates the relative distance to the target with high accuracy is provided.

  According to the present invention, since 1 CPI is not divided, it is possible to obtain a radar apparatus having improved detection performance and high distance resolution without distance ambiguity. Further, it is possible to obtain a radar apparatus that can deal with a plurality of targets.

1 is a block diagram showing a configuration of a radar apparatus according to Embodiment 1. FIG. It is explanatory drawing which shows the relationship between the frequency of a transmission signal, and time. It is explanatory drawing which shows the relationship between the transmission signal and reception signal which carried out the frequency modulation of 1CPI, and the intra-pulse code modulation. It is a figure which shows the distance map after the distance-FM ranging in PRI. It is explanatory drawing which shows the distance (when there is no target relative speed) by FM ranging, the signal after a correlation process, and the ranging result in PRI. It is explanatory drawing which shows the influence on the distance of FM ranging of the moving amount of the distance by a speed term. It is explanatory drawing which shows the conditions for solving the ambiguity of the distance in PRI of the target of the assumed maximum target relative speed. It is explanatory drawing which shows the conditions of maximum target relative distance _{Rtgt, max} assumed as distance RFM _{, amb} of FM ranging which can be measured without ambiguity. It is explanatory drawing which shows the relationship between the parameter of a transmission signal, and the distance of FM ranging. It is explanatory drawing which shows the effect on the performance of the distance of FM ranging at the time of setting conditions to the parameter of a transmission signal. It is explanatory drawing of a 4-bit Barker code. FIG. 3 is an explanatory diagram showing improvement in detection performance of the radar device according to the first embodiment. It is explanatory drawing which shows the attention cell, guard cell, and sample cell regarding a CFAR process. It is explanatory drawing which shows the processing content when the cell which exceeds a CFAR threshold value gathers as a result of CFAR processing. It is explanatory drawing which shows the transmission frequency of the conventional radar apparatus, and has shown the case where 1CPI is divided into 2 as a case of 1 target, and it processes. It is a figure explaining the transmission frequency of the conventional radar apparatus. Here, as a case of a plurality of targets, a case where processing is performed by dividing 1 CPI into three is shown.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a configuration of a radar apparatus according to Embodiment 1 of the present invention.
The radar apparatus transmits the transmission RF (high frequency) signal and switches the antenna 1, the transmitter 2, the receiver 4, the transmitter 2, and the receiver 4 to receive the reflected RF signal of the transmission RF signal to connect to the antenna 1. A transmission / reception switch 3 that performs processing of a received beat signal obtained by the receiver 4, for example, a signal processor 5 that includes a computer, and a display 6 that displays a processing result of the signal processor 5.

  The transmitter 2 includes a local oscillator 21, a pulse modulator 22, an intra-pulse modulation signal generator 23, and a transmission unit 24. The signal processor 5 is composed of a computer having a CPU, a RAM, a ROM, an interface circuit, etc., and arithmetic processing is performed by the CPU in accordance with a program stored in the ROM. The processing result of the signal processor 5 is recorded in a memory such as a RAM. The signal processor 5 includes a correlation map 52 including a correlation processing unit 52 and an FM (Frequency Modulation) ranging processing unit 53, a distance map creation unit 51 after FM ranging, a target candidate detection unit 54, and a target. The relative distance calculation unit 55 is configured.

First, the operation until the reception beat signal is generated will be described with reference to FIGS. FIG. 2 is an explanatory diagram showing processing for 1 CPI (coherent pulse interval) of the radar apparatus according to the first embodiment. FIG. 3 is an explanatory diagram showing a relationship between a transmission signal and a reception signal subjected to frequency modulation and intra-pulse code modulation of the radar apparatus according to the first embodiment.
In FIG. 2, the number of repeated transmissions of P pulse signals is referred to as the CPI number. One CPI (P = 1) performs frequency modulation over a plurality of pulses and correlation processing, that is, pulse compression processing within the PRI (RGH: Range Gated High Pulse Repetition Frequency, hereinafter referred to as RGH processing). Thus, since only one process needs to be performed for one CPI, there is no need to perform a plurality of processes as in the prior art (see FIGS. 15 and 16), and the observation time for one process is long. Thus, the detection performance can be improved.

In FIG. 3, f ₀ is a transmission start frequency, T _L is a transmission signal frequency sweep time, B _L is a transmission signal bandwidth, T ₀ beat signal observation time, B ₀ is a transmission signal bandwidth at a time interval of T ₀ , T _p transmission pulse width, φ ₀ represents the initial phase of the transmission signal and the local oscillation signal, and c represents the speed of light. The frequency modulation within the transmission signal frequency sweep time _TL will be described as up-chirp modulation.

Next, a method for setting parameters relating to transmission signals in the transmitter 2 will be described with reference to FIGS.
Specifically, the target relative distance calculation unit 55 of the signal processor 5 at the subsequent stage uses the FM ranging distance shown in FIG. 4 and the distance in the PRI to use the ambiguity (in the PRI distance as shown in FIG. In order to solve the ambiguity (ambiguity) by the distance of the FM ranging and enable distance measurement with high resolution using the distance in the PRI, the parameter of the transmission signal is set to an optimum value.
In the following description, the case where the target relative speed is 0 and the case where the target relative speed is not 0 will be described separately.

(I) When Target Relative Speed is 0 Distance resolution after correlation processing rather than distance ambiguity of distance in PRI and distance resolution of distance calculated from beat frequency (hereinafter referred to as distance by FM ranging) Distance resolution ΔR ′ _FM and sampling interval ΔR _FM by FM ranging that satisfy the following conditions (1), (2), and (3) satisfying the following expressions (1), (2), and (3), and distance resolution ΔR ′ after correlation processing _PC, the parameters for calculating the aliasing distance _{R pri} of 1PRI (beat signal observation time _T 0, _T transmission signal bandwidth _{B 0} at time intervals of _0, the pulse repetition period _{T pri,} sampling frequency _{F samp)} is set. Further, the distance resolution ΔR ′ _FM of the distance by FM ranging is the following expression (4), the sampling interval ΔR _FM of the distance by FM ranging is the following expression (5), and the return distance R _{pri in} PRI is the following expression (6). The distance resolution ΔR ′ _PC after the correlation processing is calculated by the following equation (7). Here, H represents the number of FFT points for FM ranging.
When the target relative speed can be limited to 0, the transmitter 2 operates based on the parameters set as described above.

(Ii) When the target relative speed is not 0 The FM ranging distance can be calculated from the beat frequency obtained by the FM ranging. The target beat frequency fb of the relative distance R ₀ and the relative speed v is expressed by the following formula (8).

  In equation (8), the distance term (first term on the right side) and the velocity term (second term on the right side) are mixed. In Non-Patent Document 1, in order to calculate the distance from the beat frequency, it is necessary to delete the speed term using the speed information obtained in advance (speed compensation). There has been a problem that the observation time of the processing is shortened and the detection performance is deteriorated. However, the radar apparatus according to the first embodiment can solve the distance ambiguity of the PRI internal distance without obtaining speed information in advance. Determine possible FM ranging distance conditions. Thereby, it is not necessary to obtain speed information in advance, it is possible to maintain the observation time of the RGH process for a long time, and the detection performance can be improved.

The distance R ′ _FM after FM ranging without speed compensation for the beat frequency fb is expressed by the following equation (9). As shown in Equation (9), due to the influence of the velocity term, the distance after the FM ranging is shifted and a deviation occurs, an error occurs in the number of PRI distance return, and the target relative distance cannot be calculated correctly ( (See FIG. 6).

Therefore, in the radar apparatus of the first embodiment, in order to calculate the target relative distance of the assumed maximum target relative distance R _{tgt, max} and the maximum target relative speed v _{tgt, max} , the above-described equations (1), (2 In addition to (3) and (3), the transmission signal parameters are configured to satisfy the two constraints at the same time, so that the distance is measured with high resolution without speed compensation.

As shown in FIG. 6, when speed compensation is not performed, the amount of movement of the distance becomes large due to the speed term, the number of return distances in the PRI is incorrect, and the distance cannot be accurately measured with high resolution. A parameter that satisfies the condition for solving the ambiguity of the target PRI distance within the relative speed v _{tgt, max} is set. First, the condition of the distance movement amount R _{v, move} by the speed term expressed by the following equation (10) for solving the distance ambiguity of the distance within the PRI of the target having the assumed maximum target relative speed v _{tgt, max} Set. Here, the ratio Duty of the pulse width T _p and the pulse repetition period T _pri is expressed by Expression (11).

Furthermore, in order to make it possible to measure the assumed maximum target relative distance R _{tgt, max} without ambiguity, conditions for the distance R _{FM, amb} after FM ranging without ambiguity expressed by the following equation (12) are set ( (See FIG. 8).

式（１３）が示すように、相対距離０からＲ_{ｔｇｔ，ｍａｘ}と相対速度−ｖ_{ｔｇｔ，ｍａｘ}からｖ_{ｔｇｔ，ｍａｘ}の範囲内の目標を高分解能に距離を算出することができる。 The transmitter 2 operates based on parameters of a transmission signal that simultaneously satisfy Expression (10) and Expression (12) represented by Expression (13) shown below.

As shown in Expression (13), it is possible to calculate a distance with high resolution for a target within the range of the relative distance 0 to R _{tgt, max} and the relative speed −v _{tgt, max} to v _{tgt, max} .

  With this configuration, even when there is a relative speed, it is possible to calculate the number of PRI distance wraps correctly, and the distance can be calculated with high resolution by using the PRI distance. In addition, since it is not necessary to obtain speed information in advance, it is not necessary to combine the speed of pulse Doppler processing and the beat frequency by FM ranging, and it is possible to calculate a high-resolution distance of multiple targets using all 1 CPI as RGH processing. it can.

In addition, an example of the effect of parameter setting when there is a relative speed is shown.
FIG. 9 is an explanatory diagram showing the relationship between the parameter of the transmission signal and the distance of FM ranging at different transmission frequencies.
FIG. 9A shows a case where the transmission frequency is f ₀ ′ (the range of the pulse repetition period T _pri of FIG. 9) and does not satisfy the equation (13). FIG. This is a case where the transmission frequency is f ₀ (the range of the pulse repetition period T _{pri in} FIG. 9) and satisfies the equation (13). In FIG. 9A and FIG. 9B, an example of the set parameter is indicated by ◯ ● as an example.

  FIG. 10 is an explanatory diagram showing a distance measurement result in the case of FIGS. 9A and 9B. When Expression (13) is not satisfied as shown in FIG. 9A, the influence of the speed term becomes large as shown by the parameter ◯, and the number of PRI distance wrapping is incorrect, and the distance cannot be measured correctly. On the other hand, when Expression (13) is satisfied as shown in FIG. 9B, it is possible to measure the distance with high accuracy without making an error in the number of PRI inward foldings as indicated by the parameter ●. Since the transmitter 2 of the radar apparatus according to the first embodiment is configured so that the parameter of the transmission signal satisfies the equation (13), the distance can be accurately measured as indicated by the parameter ● in FIG. . Further, it is not necessary to perform processing for obtaining speed information, the observation time of RGH processing is lengthened, and detection performance can be improved.

The local oscillator 21 generates a local oscillation signal L ₀ (t) frequency-modulated with the transmission signal frequency sweep time T _L and the transmission signal bandwidth B _L and outputs the local oscillation signal L ₀ (t) to the pulse modulator 22 and the receiver 4. The pulse modulator 22 performs pulse modulation on the local oscillation signal L ₀ (t) input from the local oscillator 21 and outputs the pulse-modulated local oscillation signal L ′ ₀ (t) to the transmission unit 24. The intra-pulse modulation signal generator 23 generates the 4-bit Barker code shown in FIG. 11 as the intra-pulse modulation signal φ (t) and outputs it to the transmission unit 24. Another bit Barker code may be used as the intra-pulse modulation signal. Further, other code modulation or frequency modulation may be used as the intra-pulse modulation signal. The transmitter 24 uses the intra-pulse modulation signal φ (t) input from the intra-pulse modulation signal generator 23 in response to the pulse-modulated local oscillation signal L ′ ₀ (t) input from the pulse modulator 22. In-pulse modulation is used to output the second transmission RF signal Tx (t) to the transmission / reception switch 3.

  The transmission / reception switch 3 outputs the transmission RF signal input from the transmission unit 24 to the antenna 1. Then, the transmission RF signal is radiated from the antenna 1 into the air. The transmission RF signal radiated into the air is reflected by the target and enters the antenna 1 as a reflected RF signal. Therefore, the antenna 1 receives the incident reflected RF signal and outputs it to the transmission / reception switch 3 as a received RF signal. The transmission / reception switch 3 outputs the reception RF signal input from the antenna 1 to the receiver 4.

The receiver 4 down-converts the second received RF signal Rx _tgt (n, t) input from the transmission / reception switch 3 using the local oscillation signal L ₀ (t) input from the local oscillator 21. Thereafter, amplification and phase detection are performed, and the result is output to the signal processor 5 as a received beat signal S (n, m) represented by the following equation (14).

なお、式（１４）において、Ａ_Ｓは受信ビート信号の振幅、ｎはビート信号観測時間Ｔ_０内のパルス番号、Ｎはビート信号観測時間Ｔ_０内の受信パルス数、ｍを１ＰＲＩ内のサンプリング番号、Ｍを１ＰＲＩ内のサンプリング点数、Δｔを１ＰＲＩ内のサンプリング時間、Ｔ_{ｏｆｆｓｅｔ}は時刻２Ｒ_{ｔｇｔ，ｍａｘ}／ｃ以上で初めての送信パルス送信開始時刻、Ｒ（ｔ）は時刻ｔの目標相対距離を表わしている。また、式（１４）における

は受信ビート信号の速度項、

は受信ビート信号の距離項、

は変調符号を表している。

In the equation (14), _{A S} is the amplitude of the received beat signal, n represents the pulse number in ₀ beat signal observation time _T, N is the sampling in 1PRI the received pulse number, m in the ₀ beat signal observation time _T No., M is the number of sampling points in 1 PRI, Δt is the sampling time in 1 PRI, T _offset is the first transmission pulse transmission start time at time 2R _{tgt, max} / c or more, and R (t) is the target relative distance at time t It represents. Moreover, in Formula (14)

Is the speed term of the received beat signal,

Is the distance term of the received beat signal,

Represents a modulation code.

Next, the processing operation of each component for the received beat signal will be described.
The distance map creation unit 51 after the distance-FM ranging in the PRI is composed of a correlation processing unit 52 and an FM ranging processing unit 53, performs correlation processing and FM ranging on the received beat signal, and calculates a relative distance from the target. A distance map within the PRI-FM range for calculation is created.

The correlation processing unit 52 performs correlation processing between the received beat signal S (n, m) and the reference signal Ex (m _τ ) expressed by the equation (14), that is, pulse compression. Here, correlation processing in the frequency domain will be described.
The reference signal Ex (m _τ ) after A / D conversion, which is the same as the intra-pulse modulation component of the transmission RF signal, is expressed by the following equation (15).

In the formula (15), m _tau sampling number, M _tau is 1PRI sampling points (see the following equation _{(16)), F samp} is the sampling frequency, floor (X) represents the maximum integer not exceeding the variable X .

The correlation processing unit 52 performs fast Fourier transform (FFT) on the received beat signal S (n, m) and the reference signal Ex (m _τ ) according to the following equations (17) and (18), respectively. , Multiply (see the following equation (19)). Here, * represents a complex conjugate, l represents a sampling number in PRI, and L ′ represents an FFT score for correlation processing. However, when L ′> M, 0 is substituted for S (n, m), and when L ′> M _τ , 0 is substituted for Ex (m _τ ).

In addition, when the correlation processing unit 52 samples the signal after the correlation processing with higher accuracy than the sampling interval of the received beat signal, the correlation processing unit 52 sets 0 according to the following equation (20). Here, L is an inverse fast Fourier transform (IFFT) point of correlation processing, and is expressed by the following equation (21). However, q is an integer greater than or equal to 0. When q = 0, the sampling interval is the same as the sampling interval of the received beat signal.

Finally, the correlation processing unit 52 performs fast Fourier inverse transform (IFFT) on the multiplication result F _{V · Ex} (n, k _r ) based on the following equation (22), and results of the correlation processing, that is, the pulse The compressed signal R _{V · Ex} (n, l) is output. Further, the relative distance R _PC (l) in PRI corresponding to the sampling number 1 of the signal R _{V · Ex} (n, l) after pulse compression is expressed by the following equation (23).

The FM ranging processing unit 53 performs IFFT on the signal R _{V · Ex} (n, l) after pulse compression by the following formula (24) at the H point in the PRI direction, and the distance map after the FM ranging. R _FM R _PC (k _h , l) is output. However, when H> N, R _{V · Ex} (n, l) is zero-padded. Sampling can be performed with high accuracy by executing IFFT with more IFFT points than the number of received pulses. Here, _{k h} represents a sampling number after FM ranging. Further, the relative distance R _FM (k _h ) between PRIs corresponding to the sampling number after FM ranging is expressed by the following equation (25).

  FIG. 16 is a diagram illustrating a transmission frequency of a conventional radar apparatus. The configuration of FIG. 16 shows a case where the FM ranging method using pulse Doppler processing and two different frequency modulations in 1 CPI is performed (1 CPI is divided into three equal parts). FIG. 12 shows a comparison result between the case where all 1 CPI of the radar apparatus of the first embodiment shown in FIG. 2 is RGH processed and the conventional configuration of FIG. 16, and after FM ranging as shown in FIG. The power of the target signal is improved and the detection performance can be improved.

  In addition, before IFFT between PRIs, for example, by multiplying a hamming window in the PRI direction, side lobes in the beat frequency direction of the clutter are suppressed, and buried in the clutter side lobes are suppressed, and detection performance is improved. be able to. A filter (FIR (Finite Impulse Response) filter or IIR (Infinite Impulse Response) filter) process that suppresses clutter in the PRI direction based on the relationship between the radar and the clutter may be used. When frequency modulation is used as an intra-pulse modulation signal, the side lobes in the PRI inner distance direction are suppressed by multiplying the reference signal by a Hamming window even during correlation processing, thereby suppressing the buried in the clutter side lobe. In addition, the detection performance can be improved.

  As described above, the distance map creation unit 51 after the distance in the PRI-FM ranging calculates the relative distance from the target by performing the intra-PRI pulse compression as the correlation process and the IFRI between the PRIs as the FM ranging. A distance map (see FIG. 4) after distance-FM ranging in PRI is output to the target candidate detection unit 54.

式（２６）で示すように、「注目セルの振幅値＞サンプルセルの振幅の平均値×ＣＦＡＲ係数」との条件を満たす場合、注目説が目標候補として検出される。 Referring to FIG. 13, the distance in the PRI - beat frequency map _{R FM R FM (k h,} l) the processing content of the target candidate detection by CFAR (Constant False Alarm Rate) processing for explaining. FIG. 13 is an explanatory diagram showing a cell of interest, a guard cell, and a sample cell related to the CFAR process.
Target candidate detection unit 54, the distance in the PRI obtained from the distance map generator 51 after the distance -FM ranging in PRI - beat frequency map _{R FM R PC (k h,} l) to the formula shown below ( 26), the target candidate is detected, and the distance R _FM (k _h ) obtained by FM ranging of the target candidate and the distance R _PC (l) in the PRI are output to the target candidate combination target relative distance calculation unit 55. . _Here, R _{FM R PC,} represents CFAR _(k h, l) is the target candidate detection result by the CFAR process, the target candidate 0 is set.

As shown in Expression (26), when the condition “amplitude value of target cell> average value of amplitude of sample cell × CFAR coefficient” is satisfied, the target theory is detected as a target candidate.

式（２７）において、ＣＦＡＲ＿ｃｏｒはＣＦＡＲ係数、Ｓａｍｐ＿ｃｅｌｌ （ｋ_ｈ，ｌ）はサンプルセル、ａｖｅ （Ｚ（ｐ））は配列Ｚ（ｐ）の平均値を表す。
ただし、図１４のようにＣＦＡＲ閾値ＣＦＡＲ＿ｔｈ（ｋ_ｈ，ｌ）を越えるセルが集合した場合は、集合のなかで振幅の最大値を示すセルを目標候補として検出する。図１４では、ＣＦＡＲ閾値ＣＦＡＲ＿ｔｈ（ｋ_ｈ，ｌ）を越えたセルを斜線領域で示している。 The CFAR threshold value CFAR_th (k _h , l) is calculated by the following equation (27).

In the formula (27), CFAR_cor is CFAR factor, Samp_cell _(k h, l) is the sample cell, ave (Z (p)) represents the average value of the sequence Z (p).
However, if you set the cell exceeds the CFAR threshold CFAR_th _(k h, l) as shown in FIG. 14, to detect the cells showing the maximum value of the amplitude among the set as a target candidate. In FIG. 14, cells that exceed the CFAR threshold value CFAR_th (k _h , l) are indicated by hatched areas.

The target relative distance calculation unit 55 calculates the distance ambiguity of the relative distance R _PC (l) within the PRI for the target candidate input from the target candidate detection unit 54 using the inter-PRI relative distance R _FM (k _h ). _Solved by the equation (28) shown below, the distance folding number N _{R, rtn} within PRI is calculated.

表示器６は、ＰＲＩ内の距離−ＦＭレンジング後の距離マップと、目標候補がある場合、目標情報として目標相対距離を画面上に表示する。 Finally, the target relative distance calculation unit 55 calculates the target relative distance R _{FM, PC} by the following equation (29) using the PRI inner distance folding number N _{R, rtn} and the PRI inner relative distance R _PC (l). Calculate and output to the display 6. Here, int (X) is the maximum integer that does not exceed the variable X.

The display 6 displays the target relative distance on the screen as target information when there is a distance map in the PRI-distance map after FM ranging and a target candidate.

  As described above, according to the first embodiment, parameters are set so that a target relative distance having a relative distance and a relative speed within an assumed range can be calculated, and frequency modulation and intra-pulse pulses for FM ranging are performed. Transmits and receives transmission RF signals that have been subjected to intra-pulse modulation for compression, and creates a distance map within the PRI-distance-FM range by performing pulse compression within the PRI and FM ranging between the PRIs for the received beat signal Then, the target candidate is calculated by the CFAR process for the distance map in the PRI-distance map after FM ranging, and the target ambiguity in the PRI of the target candidate is solved using the relative distance between the PRIs so as to calculate the target relative distance. Configured.

  Thereby, the target relative distance can be calculated without obtaining speed information in advance, and only one RGH process needs to be performed for one CPI, and the detection performance of the radar apparatus can be improved. Furthermore, a radar apparatus with high distance resolution without distance ambiguity can be obtained by solving the relative distance in PRI having distance ambiguity while maintaining high distance resolution using the relative distance between PRIs after FM ranging. Further, it is possible to obtain a radar apparatus capable of dealing with a plurality of targets and calculating a target relative distance without performing a combination of a speed by pulse Doppler processing and a beat frequency by FM ranging.

  In the present invention, any constituent element of the embodiment can be modified or any constituent element of the embodiment can be omitted within the scope of the invention.

  1 antenna, 2 transmitter, 3 transmission / reception switch, 4 receiver, 5 signal processor, 6 display, 21 local oscillator, 22 pulse modulator, 23 intra-pulse modulation signal generator, 24 transmitter, 51 in PRI A distance map creation unit after distance-FM ranging, 52 correlation processing unit, 53 FM ranging processing unit, 54 target candidate detection unit, 55 target relative distance calculation unit.

Claims (7)

In the radar device that calculates the relative distance to the target and performs target detection,
The target has a relative speed and a relative distance within a preset range, the first condition for solving the ambiguity of the target PRI distance having the relative speed, and the target PRI distance having the relative distance A parameter having a second condition in which the resolution is higher than the distance resolution after FM ranging is set, and a carrier signal that is frequency-modulated over a plurality of PRIs based on the set parameter is set in PRI. A transmitter that emits an intra-pulse modulated transmission signal;
A receiver that receives the transmission signal reflected back from the target as a reception signal, downconverts the reception signal using the carrier signal obtained from the transmitter, and converts it into a reception beat signal;
FM ranging is performed on the received beat signal obtained from the receiver, and a distance in the PRI for calculating a relative distance from the target-a distance map after the FM ranging-a distance in the PRI-a distance after the FM ranging A map creator,
A target candidate detection unit that detects a target candidate based on signal strength with respect to a distance map in the PRI-distance map after the FM ranging obtained from the distance map generation unit after the FM ranging in the PRI;
A target relative distance calculation unit that eliminates the distance ambiguity of the distance in the PRI and calculates the relative distance to the target with high accuracy by using the distance after FM ranging of the target candidate obtained from the target candidate detection unit; Radar apparatus characterized by the above.   2. The radar apparatus according to claim 1, wherein the distance map creation unit after distance-FM ranging in the PRI performs a filtering process for suppressing clutter in the PRI direction based on a relationship between the radar apparatus and the clutter. .   The radar apparatus according to claim 1, wherein the distance map creation unit after distance-FM ranging in the PRI performs window function processing in the PRI direction.   The distance map creation unit after distance-FM ranging in the PRI performs FM ranging on the received beat signal with a number of points larger than the number of received pulses of the received beat signal. Radar equipment.   The distance map creation unit after distance-FM ranging in the PRI includes a correlation processing unit that performs correlation processing that is intra-pulse modulation on a reference signal based on the received beat signal and a pulse modulation component of the transmission signal. The radar apparatus according to any one of claims 1 to 4, wherein the radar apparatus is characterized in that:   6. The radar apparatus according to claim 5, wherein the correlation processing unit performs window function processing on the reference signal after performing correlation processing in the frequency domain as the intra-pulse modulation.   The correlation processing unit performs a correlation process in the frequency domain as the intra-pulse modulation, and then performs a process of converting the signal after the correlation process into a time domain with a score larger than the sampling interval of the received beat signal The radar apparatus according to claim 5.

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