JP2015230286A - Pulse compression radar apparatus and radar signal processing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pulse compression radar apparatus capable of outputting a high-resolution range in pulse compression processing.SOLUTION: A pulse compression radar apparatus repeatedly transmitting and receiving a plurality of pulses converts reception signals of a temporal (range) axis acquired by transmitting and receiving the plurality of pulses into signals of a frequency axis, generates a pulse compressing reference signal and converts the pulse compressing reference signal into a signal of the frequency axis, generates reception signals obtained by multiplying reception signals of the frequency axis by the reference signal of the frequency axis and applying pulse compression thereto, generates a correlation matrix of the frequency axis by extracting signals of a plurality of points from the reception signal before the pulse compression, slides the correlation matrix by a plurality of cells, adds and averages the correlation matrix slid by an oblivious coefficient and generates an average correlation matrix, applies high-resolution processing to frequency axis signals applied with the pulse compression by using the average correlation matrix, and separates a target from the frequency axis signals applied with the high-resolution processing and detects the target on the temporal axis.

Description

  The present embodiment relates to a pulse compression radar apparatus that calculates a range by pulse compression and a radar signal processing method thereof.

  In the conventional pulse compression radar, the FFT result of the input signal is multiplied by the FFT result of the reference signal, and after weight multiplication, a signal exceeding a predetermined threshold is extracted and the range is output. In this case, since the range resolution is determined by the detected range cell, there is a problem that the range cannot be calculated with a resolution less than the range sample of the range axis (the range resolution determined by the frequency band of pulse compression).

Pulse compression, Yoshida, 'Revised radar technology', IEICE, pp.274-280 (1996) Pulse compression (frequency axis), Ouchi, 'Basics of Synthetic Aperture Radar for Remote Sensing', Tokyo Denki University Press, pp.131-149 (2003) Taylor distribution, Yoshida, 'Revised radar technology', IEICE, pp.134-135 (1996) CFAR (Constant False Alarm Rate) processing, Yoshida, "Revised Radar Technology", IEICE, pp.87-89 (1996) MUSIC, Kikuma, 'Adaptive Antenna Technology', Ohmsha, pp.137-164 (2003) Angle measurement method (monopulse), Yoshida, 'Revised radar technology', IEICE, pp. 260-264 (1996)

  As described above, the conventional pulse compression radar apparatus has a problem that it cannot be output with a resolution less than the range sample of the range axis (range resolution determined by the frequency band of pulse compression).

  The present embodiment has been made in view of the above problems, and an object thereof is to provide a pulse compression radar apparatus capable of outputting a range with high resolution and a radar signal processing method thereof in pulse compression processing.

  In order to solve the above-described problem, in the pulse compression radar apparatus that repeatedly transmits and receives a plurality of pulses, the present embodiment uses a time (range) axis received signal obtained by transmitting and receiving the plurality of pulses as a frequency axis signal. Converting, generating a reference signal for pulse compression, converting it to a frequency axis signal, multiplying the frequency axis reception signal by the frequency axis reference signal to generate a pulse compressed reception signal, and generating the pulse Extract a signal of multiple points from the received signal before compression to generate a correlation matrix on the frequency axis, slide the correlation matrix for each cell, and add and average with a forgetting factor to generate an average correlation matrix, and the average correlation Using the matrix, the pulse-compressed frequency-axis received signal is subjected to high-resolution processing, and the high-resolution processed frequency-axis received signal is used as a target on the time (range) axis. Separated to detect the range.

The block diagram which shows the structure of the pulse compression radar apparatus which concerns on 1st Embodiment. 2 is a flowchart showing a flow of signal processing in the radar apparatus shown in FIG. The figure for demonstrating a MUSIC spectrum process in the radar apparatus shown in FIG. The block diagram which shows the structure of the pulse compression radar apparatus which concerns on 2nd Embodiment. 5 is a flowchart showing a flow of signal processing in the radar apparatus shown in FIG. The figure for demonstrating the process of the radar apparatus shown in FIG. The block diagram which shows the structure of the pulse compression radar apparatus which concerns on 3rd Embodiment. 8 is a flowchart showing the flow of signal processing in the radar apparatus shown in FIG. The figure for demonstrating the process of the radar apparatus shown in FIG. The block diagram which shows the structure of the pulse compression radar apparatus which concerns on 4th Embodiment. 11 is a flowchart showing a flow of signal processing in the radar apparatus shown in FIG. The figure for demonstrating the process of the radar apparatus shown in FIG. The block diagram which shows the structure of the pulse compression radar apparatus which concerns on 5th Embodiment. 14 is a flowchart showing a flow of signal processing in the radar apparatus shown in FIG. The figure for demonstrating the process of the radar apparatus shown in FIG. The block diagram which shows the structure of the pulse compression radar apparatus which concerns on 6th Embodiment. 17 is a flowchart showing a signal processing flow in the radar apparatus shown in FIG. The figure for demonstrating the process of the radar apparatus shown in FIG. The block diagram which shows the structure of the pulse compression radar apparatus which concerns on 7th Embodiment. 20 is a flowchart showing a flow of signal processing in the radar apparatus shown in FIG.

  Hereinafter, embodiments will be described with reference to the drawings. In the description of each embodiment, the same portions are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment)
Hereinafter, the pulse compression radar apparatus according to the first embodiment will be described with reference to FIGS. 1 to 3.

  FIG. 1 is a block diagram showing a system configuration of the radar apparatus, FIG. 2 is a flowchart showing a specific processing flow thereof, and FIG. 3 is a diagram for explaining MUSIC spectrum processing applied to the radar apparatus.

  In the radar apparatus shown in FIG. 1, the antenna 1 is a phased array antenna in which a plurality of antenna elements are arranged to form a large aperture array, and a transmission pulse having a specific frequency that is repeatedly supplied from the transmitter / receiver 21 of the transmitter / receiver 2. A signal (hereinafter referred to as a PRF (Pulse Repetition Frequency) signal) is transmitted in a designated direction and the reflected wave is received. In the transmitter / receiver 2, the transmitter / receiver 21 forms a received beam in an arbitrary direction by performing phase control on the signals respectively received by the plurality of antenna elements of the antenna 1 according to instructions from the beam controller 22 and combining them. The PRF received signal is acquired, and the frequency is converted to the baseband (FIG. 2: step S11). The PRF reception signal thus obtained is sent to the signal processor 3.

  The signal processor 3 includes an AD (Analog-Digital) converter 31, a range axis FFT (Fast Fourier Transformation) processor 32, a multiplier 33, a reference signal generator 34, a reference signal FFT processor 35, and an average correlation matrix calculation. A unit 36, a MUSIC (Multiple Signal Classification) processing unit 37, a CFAR detection unit 38, and a range calculation unit 39.

  In the signal processor 3, the reception signal frequency-converted by the transmission / reception unit 21 is converted into a digital signal by the AD conversion unit 31 (FIG. 2: step S12). The AD-converted signal is subjected to FFT processing on the range axis by the range axis FFT processing unit 32 (FIG. 2: step S13) and sent to the multiplication unit 33. On the other hand, the reference signal generator 34 generates a reference signal for pulse compression (FIG. 2: step S14), and this reference signal is subjected to FFT processing in the FFT processor 35 (FIG. 2: step S15). It is sent to the multiplier 33. The multiplier 33 multiplies the frequency domain signal obtained by the range axis FFT processing of the received signal by the frequency domain signal obtained by the FFT processing of the reference signal (FIG. 2: step S16), and the frequency subjected to pulse compression. Convert to a band signal. This pulse compression signal is sent to the average correlation matrix calculator 36.

  The average correlation matrix calculation unit 36 extracts a frequency cell from the pulse compression signal (FIG. 2: step S17), and calculates an average correlation matrix due to frequency cell movement (FIG. 2: steps S18 and S19). The average correlation matrix obtained here suppresses mutual correlation components of a plurality of target signals by MUSIC processing (FIG. 2: step S20). The result is sent to the CFAR detection unit 38, and after the maximum value ωt of the signal exceeding the threshold is detected by the CFAR process (FIG. 2: step S21), the target range (distance information) Rt is calculated by the range calculation unit 39. (FIG. 2: Step S22).

  In the above configuration, the operation will be described with reference to FIG.

  First, the signal transmitted / received by the antenna 1 is directed to the target direction by the beam control unit 22, and the received signal of the beam is input to the signal processor 3. In the signal processor 3, after the beam reception signal is converted into a digital signal by the AD conversion unit 31, the range axis FFT processing unit 32 performs FFT processing on the range axis and performs pulse compression. Further, a reference signal for pulse compression is generated by the reference signal generation unit 34, the reference signal is subjected to FFT processing by the FFT processing unit 35, and this signal and the input signal FFT result are multiplied by the multiplication unit 33. The above processing can be expressed by mathematical formulas as follows.

First, the input signal sig (t) is subjected to FFT processing.

Next, when a reference signal (in the case of a linear chirp signal) is expressed, the following expression is obtained.

Needless to say, the reference signal may be another modulation method such as a non-linear chirp signal or code modulation (see Non-Patent Documents 1 and 2). The sample length of the reference signal Sref (t) is replaced with a zero-padded signal in accordance with the input signal.

This is FFTed to obtain a frequency domain signal of the reference signal.

Thereby, the signal after multiplication in the frequency domain is expressed by the following equation.

Next, a weight for reducing the range side lobe after pulse compression is calculated. For the weight, a uniform weight, a Taylor weight (see Non-Patent Document 3), or the like may be selected according to the setting of the range side lobe.

Next, using this Sw (ω) (corresponding to signal X, frequency axis), MUSIC processing is performed (see Non-Patent Document 4). Since multiple target signals by radar transmission / reception are correlated with each other, Nr cells are sequentially extracted from the Sw signal length in order to suppress the correlation component of the Sw correlation matrix Rxx, and Rxx is calculated each time. I do.

Next, Rxx (n, ω) is calculated by an average process using a forgetting factor.

  Note that Rxx (n, w) is calculated by clearing each CPI (Coherent Pulse Interval: n hit processing, 1 hit in the first embodiment) and without clearing Rxx of the previous CPI. Needless to say, the calculation of the equation (8) may be continued as it is. The effect of continuing is that since the time is long, the phase changes due to the change in the relative position due to the acceleration difference between the targets, and the correlation is easily suppressed.

A MUSIC spectrum is calculated using this Rxx (n, w) (see Non-Patent Document 5).

An explanation of the above processing is shown in FIG. 3, (a) is the input signal, (b) is the range FFT result, (c) is the reference signal, (d) is the range FFT result, (e) is the multiplication result of (b) and (d). , (F) shows the MUSIC spectrum calculation result Smusic by the average value of Rxx in (e). In this spectrum Smusic, for example, the maximum value ωt of the signal exceeding the threshold is extracted by CFAR processing (see Non-Patent Document 4), and the target range Rt is calculated by conversion of the following equation.

  As described above, the pulse compression radar apparatus according to the first embodiment performs FFT processing on the acquired range axis signal, generates a reference signal for pulse compression, performs FFT processing, and multiplies both. By extracting the Nr point signal with respect to the previous frequency axis signal to generate a frequency axis correlation matrix Rxx, sliding it by Mr cells, and using Rxx obtained by adding and averaging with the forgetting factor, The target is separated and detected by the range axis. According to this configuration, a range can be output with a resolution equal to or lower than the range sample even with a target signal having a correlation between radar transmission and reception signals by MUSIC processing using a correlation matrix based on a moving average of the frequency axis.

(Second Embodiment)
The second embodiment will be described with reference to FIGS. 4 to 6.
In the first embodiment, the method for improving the range resolution by the MUSIC method using the signal vector (Nr dimension) of multiplication of the signal before pulse compression and the reference signal has been described. In this case, if Nr is large, there is a problem that the number of dimensions of the correlation matrix is large and the calculation scale increases. In order to solve the problem, the second embodiment is a method of processing by reducing the number of target range cells.

  FIG. 4 is a block diagram showing the system configuration of the pulse compression radar apparatus according to the second embodiment, FIG. 5 is a flowchart showing the specific processing flow, and FIG. 6 is a diagram for explaining the signal processing. .

  4 and 5, the difference from the first embodiment is that the output of the multiplication unit 33 is IFFT processed for the range axis by the range axis IFFT processing unit 3A (FIG. 5: step S23), thereby generating a time domain signal. Then, the CFAR detection unit 3B performs CFAR processing (FIG. 5: step S24), detects the maximum value of the signal exceeding the threshold, and the range cell extraction unit 3C extracts the range cell corresponding to the maximum value (FIG. 5: In step S25), the range axis FFT processing unit 3D returns the signal to the frequency domain signal by the range axis FFT processing (FIG. 5: step S26) and inputs the signal to the above-described average correlation matrix calculation unit 36.

In this embodiment, Equations (1) to (6) are the same as those in the first embodiment, and Sw (ω) can be calculated. Next, this is inverse FFTed to obtain the following equation.

The relationship between the time axis t and the range axis R is given by the following equation. When ranges and times are notated in the following, they are converted according to the relationship of the equation (12).

  CFAR processing is performed on this time (range) axis signal S (t) (expressed in time), and a time Tsel (p) (p is a target number) at which detection has been completed is extracted. Using the ± Pr cells around this extraction cell, the input signal Sinw (number of cells 2 × Pr + 1) obtained by performing the range axis FFT to the frequency axis is used to detect the target by the same processing as in the first embodiment. Detect time (range) cells. When there are a plurality of detection times Tsel (p), the process may be performed for each time (range) cell range corresponding to the number. The state of this processing is shown in FIG. 6A shows the range selection result after pulse compression, FIG. 6B shows the range axis FFT processing result of the range selection result, and FIG. 6C shows the frequency domain signal subjected to the range axis FFT processing. FIG. 6D shows a state in which a multi-target MUSIC spectrum is obtained by MUSIC based on the average value of Rxx for the MUSIC processing result.

  As described above, in the pulse compression radar apparatus according to the second embodiment, after pulse compression (range axis), P targets are detected by CFAR processing, and ± Pr ranges centered on the P range cells. The signal corresponding to is subjected to FFT processing and converted to the frequency axis, and the Nr point signal is extracted to generate the frequency axis correlation matrix Rxx, and it is slid for each Mr cell, and Rxx obtained by averaging by the forgetting factor is obtained. The target is separated and detected on the range axis by the MUSIC process to be used. In this case, the target scale having the correlation of the radar transmission / reception signal is reduced by the MUSIC process using the correlation matrix based on the moving average of the frequency axis with respect to the range in the vicinity where the target exists. The range can be output with a resolution of.

(Third embodiment)
A third embodiment will be described with reference to FIGS.
In the first embodiment, the method for improving the range (time) resolution by performing the MUSIC process on the frequency axis signal before the pulse compression has been described. When the SN (signal to noise ratio) of the target signal is low, the MUSIC spectrum may be blurred and the target cannot be separated. In order to solve this problem, the third embodiment describes a technique for improving SN by integration using a PRI-axis FFT.

  FIG. 7 is a block diagram showing the system configuration of the pulse compression radar apparatus according to the third embodiment, FIG. 8 is a flowchart showing the specific processing flow, and FIG. 9 is a diagram for explaining the signal processing. .

  7 and 8, the difference from the first embodiment is that the time domain signal is obtained by subjecting the output of the AD conversion unit 31 to FFT processing for the PRI axis by the PRI axis FFT processing unit 3E (FIG. 8: step S27). The CFAR detection unit 3F performs CFAR processing (FIG. 8: step S28), detects the maximum value of the signal exceeding the threshold, and selects the bank corresponding to the maximum value in the bank selection unit 3G (see FIG. 8: Step S29) and input to the above-described range axis FFT processing unit 32.

That is, in the third embodiment, first, the input signal sig (n, t) (PRI number, time) is subjected to FFT processing on the PRI axis.

CFAR processing is performed for each bank, and a bank in which a signal is detected is set to nd.

  By applying the third embodiment using this sig (t) as an input and performing FFT processing on the PRI axis, a MUSIC spectrum can be calculated from a signal having a high SN.

  As described above, in the third embodiment, in the pulse compression radar apparatus that transmits and receives N pulses, as shown in FIG. 9A, FFT processing is performed on the received signal of N pulses in the PRI axis direction, and FIG. ), A frequency bank having an extreme value is selected by CFAR processing, a range axis signal for the bank is extracted and FFT processed, and a reference signal for pulse compression is generated and FFT processed. The frequency axis correlation matrix Rxx is generated by extracting the Nr point signal from the frequency axis signal before pulse compression multiplied by, and Rxx is generated by sliding it on the Mr cell basis, and added by the forgetting factor. The target is separated and detected by the range axis by MUSIC processing using the averaged Rxx. That is, SN (Signal to Noise ratio) is increased by PRI axis FFT, and MUSIC processing is performed using a correlation matrix based on a moving average of the frequency axis. Therefore, a target having a small amplitude having a correlation between radar transmission and reception signals. Even a signal can output a range with a resolution less than the range sample.

(Fourth embodiment)
The fourth embodiment will be described with reference to FIGS. 10 to 12.
The fourth embodiment is a method of extracting range cells by adopting the method of the second embodiment in order to reduce the processing scale in the third embodiment. FIG. 10 is a block diagram showing a system configuration of a pulse compression radar apparatus according to the fourth embodiment, FIG. 11 is a flowchart showing a specific processing flow, and FIG. 12 is a diagram for explaining the signal processing. .

  10 and 11 is characterized in that the output of the AD conversion unit 31 is subjected to FFT processing for the PRI axis by the PRI axis FFT processing unit 3E with respect to the configuration of the first embodiment (FIG. 11: Step S27). ) To convert to a time domain signal, and CFAR processing is performed by the CFAR detection unit 3F (FIG. 11: Step S28). The maximum value of the signal exceeding the threshold is detected, and the bank corresponding to the maximum value is detected by the bank selection unit 3G. Is selected (FIG. 11: step S29) and input to the above-described range axis FFT processing unit 32, and the output of the multiplication unit 33 is IFFT processed for the range axis by the range axis IFFT processing unit 3A (FIG. 11: In step S23), the signal is converted into a time domain signal, and the CFAR detection unit 3B performs CFAR processing (FIG. 11: step S24). The maximum value of the signal exceeding the threshold value The range cell corresponding to the maximum value is detected by the range cell extracting unit 3C (FIG. 11: Step S25), and the frequency domain signal is obtained by the range axis FFT processing (FIG. 11: Step S26) by the range axis FFT processing unit 3D. In other words, the average correlation matrix calculation unit 36 inputs the information.

  That is, in the pulse compression radar apparatus according to the fourth embodiment, N pulses are transmitted / received as shown in FIG. 12A, FFT processing is performed in the PRI axis direction of the N pulses as shown in FIG. Further, a frequency bank having P extreme values is selected by CFAR processing using the signal after pulse compression as shown in FIG. 12 (c), and the range for each frequency bank is shown in FIG. 12 (d). Of the axis signals, the signals corresponding to ± Pr ranges centered on P range cells are FFT processed and converted to the frequency domain, and Nr point signals are extracted to generate the frequency axis correlation matrix Rxx. Then, it is slid by Mr cells, and as shown in FIG. 12E, the target is separated and detected by the range axis by the MUSIC process using Rxx obtained by averaging with the forgetting factor. Thus, the SN is improved by FFT processing, the bank is extracted by CFAR processing, the range range is selected from the range axis signals of the bank, and the frequency axis is obtained by performing FFT on the range axis signal. The method of the third embodiment is applied to this frequency axis signal. In the present embodiment, since the bank corresponding to the maximum value is selected, the frequency cell extraction process in step S17 shown in FIG. 8 is not necessary.

  As described above, in the fourth embodiment, the SN (Signal to Noise ratio) is increased by the FFT processing of the PRI axis, the range cell in the vicinity where the target exists is extracted, and the correlation matrix by the moving average of the frequency axis Since the MUSIC processing using the signal is performed, even with a target signal having a small amplitude and having a correlation between radar transmission and reception signals, the processing scale can be reduced and the range can be output with a resolution equal to or lower than the range sample.

(Fifth embodiment)
The fifth embodiment will be described with reference to FIGS. 13 to 15.
The fifth embodiment is a method of extracting range cells by adopting the method of the second embodiment in order to reduce the processing scale in the third embodiment. FIG. 13 is a block diagram showing a system configuration of a pulse compression radar apparatus according to the fifth embodiment, FIG. 14 is a flowchart showing a specific processing flow, and FIG. 15 is a diagram for explaining the signal processing. .

  13 and FIG. 14 is characterized in that the range axis FFT processing unit 3D (step S26 in FIG. 12) shown in FIG. 10 is omitted, and the average correlation matrix calculation unit 36 calculates the average Rxx between the CPIs. (Step S30 in FIG. 14).

  That is, in the fifth embodiment, the MUSIC process is performed on the frequency axis signal before the pulse compression in the first to fourth embodiments, whereas the range axis signal after the pulse compression is performed. MUSIC processing. Thereby, since the MUSIC process can be performed using a signal in the vicinity of the range including the target signal, the processing scale can be reduced.

  FIG. 13 describes a method corresponding to the fourth embodiment as a method using a signal before pulse compression. As described above, as compared with FIG. 10 of the fourth embodiment, the part where the range axis FFT processing unit 3D subsequent to the range cell extracting unit 3C is not provided is different. In this method, the point of MUSIC processing using the signal after pulse compression is the point, so that portion will be described below. The range cell extraction portion and the PRI axis FFT processing portion are shown in FIG. The description will be omitted as shown in FIG.

First, the signal before pulse compression is the same as that in the equations (1) to (6), and the equation (6) is re-displayed as the equation (15).

Next, a signal after pulse compression is obtained by performing inverse FFT on this.

  Next, the MUSIC process is performed using the Swr (t) (corresponding to the signal X). In the processing of the first embodiment, the processing is performed on the frequency axis, and in the frequency axis, the range of each target is replaced with a phase gradient. Therefore, in order to suppress the correlation between the radar targets, the elements of Swr are sequentially arranged in the Nr cell. Sliding was extracted one by one and the correlation was suppressed by the average value. On the other hand, in the present embodiment, the processing is performed on the range axis, and the target exists only in each range, so the method of sliding the range axis is meaningless. For this reason, the decorrelation between radar targets is based on an average process between CPIs.

In addition, in this embodiment, there is an advantage that the processing scale can be reduced by limiting the range cells. Therefore, the cells extracted by the CFAR detection unit 3B and the range cell extraction unit 3C are defined as P (P is a plurality), and ± Pr cell extraction is performed. This is defined as Swr (t) (Nr dimension Nr = 2 * Pr + 1).

Next, Rxx (n, t) is calculated by an average process using a forgetting factor (FIG. 15 (d)).

This Rxx (n, t) is replaced with Rxx (Nr × Nr dimension) to calculate a MUSIC spectrum.

  In this spectrum Smusic, for example, as shown in FIG. 15E, if the maximum value t of the signal exceeding the threshold is extracted by the CFAR process, the range can be output according to the relationship of the expression (12).

  As described above, in the pulse compression radar apparatus according to the fifth embodiment, the correlation matrix Rxx is generated using the signal after pulse compression, and the MUSIC process using Rxx obtained by averaging the CPIs with the forgetting factor, The target is detected separately on the range axis. For this reason, the range can be output with a resolution equal to or lower than the range sample even with the target signal having the correlation between the radar transmission and reception signals by the MUSIC processing using the correlation matrix based on the moving average of the range axis.

  Further, in the fifth embodiment, P target is detected by performing CFAR processing after pulse compression, and Rxx is used by using signals after pulse compression corresponding to ± Pr ranges around the P range cells. And the target is separated and detected on the range axis by MUSIC processing using Rxx obtained by averaging between CPIs using the forgetting factor. For this reason, the processing scale of the target signal having the correlation of the radar transmission / reception signal is reduced by the MUSIC processing using the correlation matrix based on the moving average of the range axis not performing FFT on the nearby range where the target exists. A range can be output with a resolution less than the range sample.

  Further, in the fifth embodiment, in a pulse compression radar apparatus that transmits and receives N pulses, FFT processing is performed in the PRI axis direction of N pulses, a range axis signal for a frequency bank having extreme values is extracted by CFAR, and pulse compression is performed. Then, by generating a correlation matrix Rxx and performing MUSIC processing using Rxx obtained by averaging with a forgetting coefficient between CPIs, it is possible to detect the target separately on the range axis. Thereby, SN (Signal to Noise ratio) is increased by the FFT of the PRI axis, and the target signal having a small amplitude with the correlation of the radar transmission / reception signal is obtained by the MUSIC process using the correlation matrix by the moving average of the range axis without the FFT. However, it is possible to output a range with a resolution less than the range sample.

  Further, in the fifth embodiment, in a pulse compression radar apparatus that transmits and receives N pulses, a frequency having P extreme values by CFAR using a signal after FFT in the PRI axis direction of N pulses and further pulse compression. Of the range axis signals for the bank, a signal corresponding to ± Pr ranges centered on P range cells is extracted to generate a frequency axis correlation matrix Rxx, and Rxx is obtained by averaging the CPI with the forgetting factor By MUSIC processing using, the target is separated and detected on the range axis. Radar transmission / reception signal by MUSIC processing using a correlation matrix based on moving average of range axis without FFT, extracting SN cell with high signal-to-noise ratio (SN) by PRI axis FFT Even with a target signal having a small amplitude and a correlation, the processing scale can be reduced and the range can be output with a resolution equal to or lower than the range sample.

(Sixth embodiment)
The sixth embodiment will be described with reference to FIGS. 16 to 18.
The sixth embodiment is a method for measuring angles of Az and EL. FIG. 16 is a block diagram showing a system configuration of a pulse compression radar apparatus according to the sixth embodiment, FIG. 17 is a flowchart showing a specific processing flow, and FIG. 18 is an explanatory diagram thereof.

  16 and FIG. 17 is characterized in that a phase monopulse signal (Σ, Δ: see Non-Patent Document 6) is used in the transmission / reception unit 21 for angle measurement, and each of the Σ and Δ signals is converted into an AD conversion unit 31. Then, the Σh generator 3H generates a first signal Σh1 and a second signal Σh2 that are divided into two apertures, and distributes and outputs them to the two systems (FIG. 17: step S31), and a Σ1 formation unit 3I1 The Σ1 beam and the Σ2 beam having different directivity directions are formed by the Σ2 forming unit 3I2 (FIG. 17: steps S32 and S32 ′), and the PRI axis FFT processing units 3E1 and 3E2 respectively perform FFT processing in the PRI axis direction (FIG. 17). : Steps S33, S33 ').

  Thereafter, the FFT processing in the range axis direction of the range axis FFT processing units 3E1 and 3E2 (FIG. 17: Steps S13 and S13 ′), the multiplication with the reference signal FFT processing signal of the multiplication units 331 and 332, the range axis IFFT processing unit 3A1, 3A2 inverse FFT processing in the range axis direction (FIG. 17: steps S23, S23 ′), maximum detection processing of CFAR detectors 3B1, 3B2 (FIG. 17: steps S24, S24 ′), maximum value of range cell extraction units 3C1, 3C2 Cell detection processing (FIG. 17: steps S25, S25 ′), FFT processing in the range axis direction of the range axis FFT processing units 3D1, 3D2 (FIG. 17: steps S26, S26 ′), average correlation matrix calculation unit 361 , 362 (FIG. 17: steps S18 to S19, S18 ′ to S19 ′), MUSIC processing unit 371, 72 (FIG. 17: Steps S20 and S20 ′), CFAR detectors 381 and 382 (FIG. 17: Steps S21 and S21 ′), and range calculators 391 and 392 (FIG. 17: Step S22) are sequentially executed. The angle measurement value calculation unit 3J performs angle measurement (FIG. 17: step S34).

That is, in the sixth embodiment, phase monopulse signals (Σ, Δ: Non-Patent Document 6) are used for angle measurement.

Therefore, when the phase monopulse output signals are Σ and Δ, S1 and S2 can be calculated by the following equations.

If a phase that determines the beam directing direction is set in S1 and S2, a Σ1 beam and a Σ2 beam having different directing directions can be formed.

Using the signals of b1 and b2 as input signals sig1 and sig2, the range r is calculated from the extreme values of each MUSIC spectrum by the method of the first embodiment, and by this r, the power (b1, b2 S1 and S2) are calculated corresponding to (see Non-Patent Document 5).

The received power (P1 and P2) for the pth target is obtained from the pth diagonal component of the matrix S (S1 and S2), and the received amplitude (E1 and E2) is obtained by the square root. Using this, the error voltage is calculated by the following equation.

  As for the error voltage and the angle, as shown in FIGS. 18A and 18B, the error voltage with respect to the angle is tabulated in advance based on the relationship of Σ1 and Σ2, and an error voltage table is created. The angle θ is calculated using a table from ε calculated by the equation (24).

In the case of a three-dimensional radar, it goes without saying that the above-described method may be used for the Az plane and the EL plane, respectively.
Although the present invention has been described with respect to the MUSIC technique, it goes without saying that a ROOT-MUSIC or ESPRIT (see Non-Patent Document 5) method, which is a known technique, may be used to reduce the processing scale.

(Seventh embodiment)
The seventh embodiment will be described with reference to FIGS. 19 to 20.
The seventh embodiment is also a method for measuring angles of Az and EL. FIG. 19 is a block diagram showing a system configuration of a pulse compression radar apparatus according to the seventh embodiment, and FIG. 20 is a flowchart showing a specific processing flow thereof.

  19 and 20 are different from FIGS. 16 and 17 in that the range axis FFT processing units 3D1 and 3D2 subsequent to the range cell extraction units 3C1 and 3C2 are not employed. That is, similarly to the fifth embodiment, the range cell is extracted by adopting the method of the second embodiment in order to reduce the processing scale.

  In the sixth and seventh embodiments, in the pulse compression radar apparatus that divides the antenna aperture into two and transmits / receives pulses using the sum (Σ) and difference (ΔAz or ΔEL) beams, the left and right (up and down) sides of the Σ and Δ signals. An aperture signal is generated, a phase for directing the beam in a predetermined direction is given by the signal to form two Σ beams (Σ1 and Σ2), and the processing of the first to fifth embodiments is performed by Σ1 and Σ2. Then, the corresponding range cell of the MUSIC spectrum is extracted, and the angle is measured using the error voltage due to the amplitude ratio of the MUSIC spectrum of Σ1 and Σ2.

  In other words, by MUSIC processing using a correlation matrix based on a moving average of the range axis, a target signal having a correlation between radar transmission and reception signals is output with a resolution equal to or lower than the range sample, and two beams using Σ and Δ monopulse outputs. The angle can be measured by the output of.

  Note that the present embodiment is not limited to the above-described embodiment as it is, and can be embodied by modifying constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  DESCRIPTION OF SYMBOLS 1 ... Phased array antenna, 2 ... Transmitter / receiver, 21 ... Transmitter / receiver, 22 ... Beam controller, 3 ... Signal processor, 31 ... AD (Analog-Digital) converter, 32 ... Range axis FFT (Fast Fourier Transformation) processing 33: Multiplier, 34 ... Reference signal generator, 35 ... Reference signal FFT processor, 36 ... Average correlation matrix calculator, 37 ... MUSIC (Multiple Signal Classification) processor, 38 ... CFAR detector, 39 ... Range Calculation unit, 3A ... range axis IFFT processing unit, 3B ... CFAR detection unit, 3C ... range cell extraction unit, 3D ... range axis FFT processing unit, 3E ... PRI axis FFT processing unit, 3F ... CFAR detection unit, 3G ... bank selection unit 3H ... Σh generator, 3I1 ... Σ1 formation unit, 3I2 ... Σ2 formation unit, 3E1, 3E2 ... PRI axis FFT processing unit, 3E1, 3E2 ... range axis FFT processing unit, 33 332: Multiplier 3A1, 3A2 Range axis IFFT processor 3B1, 3B2 CFAR detector 3C1, 3C2 Range cell extractor 3D1, 3D2 Range axis FFT processor 361, 362 Average correlation matrix calculation , 371, 372... MUSIC processing unit, 381, 382... CFAR detection unit, 391, 392... Range calculation unit, 3J.

Claims (20)

In a pulse compression radar device that repeatedly transmits and receives a plurality of pulses,
Means for converting a reception signal on the time (range) axis acquired by transmission and reception of the plurality of pulses into a signal on the frequency axis;
Means for generating a reference signal for pulse compression and converting it to a frequency axis signal;
Means for multiplying the frequency axis received signal by the frequency axis reference signal to generate a pulse-compressed received signal;
A signal of a plurality of points is extracted from the received signal before the pulse compression to generate a frequency axis correlation matrix, the correlation matrix is slid by a plurality of cells, and an average correlation matrix is generated by averaging with a forgetting factor. Means,
Means for high-resolution processing of the pulse-compressed frequency axis received signal using the average correlation matrix;
A pulse compression radar apparatus comprising: means for separating a target on the time (range) axis from the received signal on the frequency axis subjected to the high resolution processing and detecting the range.   The means for generating the average correlation matrix detects a prescribed number of targets by converting the pulse-compressed received signal into a time (range) axis signal and performing CFAR (Constant False Alarm Rate) processing, A frequency axis correlation matrix is generated by extracting a signal of the plurality of points by converting a signal corresponding to an arbitrary number of ranges before and after the target range cell of the number into a received signal of the frequency axis and extracting the signals of the plurality of points. Item 2. The pulse compression radar apparatus according to Item 1. In a pulse compression radar device that repeatedly transmits and receives a plurality of pulses,
Means for converting the received signal of the time (range) axis acquired by transmission and reception of the plurality of pulses into a frequency axis signal in the axial direction of the repetition period of the plurality of pulses;
Means for performing CFAR (Constant False Alarm Rate) processing on the received signal converted to the frequency axis, extracting a time (range) axis received signal for a frequency bank having an extreme value, and converting the received signal to a frequency axis signal;
Means for generating a reference signal for pulse compression and converting it to a frequency axis signal;
Means for generating a pulse-compressed received signal by multiplying the frequency-axis received signal for the frequency bank having the extreme value by the frequency-axis reference signal;
A signal of a plurality of points is extracted from the received signal before the pulse compression to generate a frequency axis correlation matrix, the correlation matrix is slid by a plurality of cells, and an average correlation matrix is generated by averaging with a forgetting factor. Means,
Means for high-resolution processing of the received signal on the frequency axis for the frequency bank having the extreme value, the pulse compression using the average correlation matrix;
A pulse compression radar apparatus comprising: means for separating a target on the time (range) axis from the received signal on the frequency axis subjected to the high resolution processing and detecting the range.   The means for generating the average correlation matrix detects a prescribed number of targets by converting the pulse-compressed received signal into a time (range) axis signal and performing CFAR (Constant False Alarm Rate) processing, A frequency axis correlation matrix is generated by extracting a signal of the plurality of points by converting a signal corresponding to an arbitrary number of ranges before and after the target range cell of the number into a received signal of the frequency axis and extracting the signals of the plurality of points. Item 4. The pulse compression radar apparatus according to Item 3. In a pulse compression radar device that repeatedly transmits and receives a plurality of pulses,
Means for converting a reception signal on the time (range) axis acquired by transmission and reception of the plurality of pulses into a signal on the frequency axis;
Means for generating a reference signal for pulse compression and converting it to a frequency axis signal;
Means for multiplying the frequency axis received signal by the frequency axis reference signal to generate a pulse-compressed received signal;
Means for generating a correlation matrix from the pulse-compressed received signal and generating an average correlation matrix by averaging between CPIs (Coherent Pulse Intervals) using a forgetting factor;
Means for high-resolution processing of the pulse-compressed received signal using the average correlation matrix;
A pulse compression radar apparatus comprising: means for separating a target on the time (range) axis from the received signal subjected to the high resolution processing and detecting the range.   The means for generating the average correlation matrix detects a prescribed number of targets by converting the pulse-compressed received signal into a time (range) axis signal and performing CFAR (Constant False Alarm Rate) processing, 6. The pulse compression radar apparatus according to claim 5, wherein a signal corresponding to an arbitrary number of ranges before and after the number of target range cells is extracted to generate a correlation matrix of the time (range) axis. In a pulse compression radar device that repeatedly transmits and receives a plurality of pulses,
Means for converting the received signal of the time (range) axis acquired by transmission and reception of the plurality of pulses into a frequency axis signal in the axial direction of the repetition period of the plurality of pulses;
Means for performing CFAR (Constant False Alarm Rate) processing on the received signal converted to the frequency axis, extracting a time (range) axis received signal for a frequency bank having an extreme value, and converting the received signal to a frequency axis signal;
Means for generating a reference signal for pulse compression and converting it to a frequency axis signal;
Means for generating a pulse-compressed received signal by multiplying the frequency-axis received signal for the frequency bank having the extreme value by the frequency-axis reference signal;
Means for generating a correlation matrix from the pulse-compressed received signal and generating an average correlation matrix by averaging between CPIs (Coherent Pulse Intervals) using a forgetting factor;
Means for high-resolution processing of the received signal on the time (range) axis for the frequency bank having the extreme value, which is pulse-compressed using the average correlation matrix;
A pulse compression radar apparatus comprising: means for separating a target on the time (range) axis from the received signal on the time (range) axis subjected to the high resolution processing and detecting the range.   The means for generating the average correlation matrix detects a prescribed number of targets by converting the pulse-compressed received signal into a time (range) axis signal and performing CFAR (Constant False Alarm Rate) processing, 8. The pulse compression radar apparatus according to claim 7, wherein a signal corresponding to an arbitrary number of ranges before and after the number of target range cells is extracted to generate a correlation matrix of the time (range) axis. In a pulse compression radar device that divides an antenna aperture into two and repeatedly transmits and receives a plurality of pulses by a sum (Σ) beam and a difference (ΔAZ or ΔEL) beam,
Means for generating a pair of aperture signals from a Σ signal by the sum (Σ) beam and a Δ signal by the difference (ΔAZ or ΔEL) beam;
Means for providing a phase for directing a beam in a predetermined direction by the Σ signal and the Δ signal to form two sum beams, and generating a Σ1, Σ2 signal from the received signals of each beam;
Means for calculating an error voltage based on an amplitude ratio of both signals by performing the high resolution processing on the frequency axis by performing the processing according to any one of claims 1 to 4 on the Σ1 and Σ2 signals;
A pulse compression radar apparatus comprising: means for obtaining an angle measurement value from the error voltage. In a pulse compression radar device that divides an antenna aperture into two and repeatedly transmits and receives a plurality of pulses by a sum (Σ) beam and a difference (ΔAZ or ΔEL) beam,
Means for generating a pair of aperture signals from a Σ signal by the sum (Σ) beam and a Δ signal by the difference (ΔAZ or ΔEL) beam;
Means for providing a phase for directing a beam in a predetermined direction by the Σ signal and the Δ signal to form two sum beams, and generating a Σ1, Σ2 signal from the received signals of each beam;
Means for calculating an error voltage based on an amplitude ratio of both signals by performing the processing according to any one of claims 5 to 8 on the Σ1 and Σ2 signals and performing high-resolution processing on a time axis;
A pulse compression radar apparatus comprising: means for obtaining an angle measurement value from the error voltage. In a signal processing method of a pulse compression radar apparatus that repeatedly transmits and receives a plurality of pulses,
The time (range) axis received signal obtained by transmitting and receiving the plurality of pulses is converted into a frequency axis signal,
Generate a reference signal for pulse compression and convert it to a frequency axis signal.
Multiplying the frequency axis reception signal by the frequency axis reference signal to generate a pulse-compressed reception signal;
A signal of a plurality of points is extracted from the received signal before the pulse compression to generate a frequency axis correlation matrix, the correlation matrix is slid by a plurality of cells, and an average correlation matrix is generated by averaging with a forgetting factor. ,
Using the average correlation matrix, the pulse-compressed frequency axis received signal is processed with high resolution,
A signal processing method for a pulse compression radar apparatus, in which a target is separated on a time (range) axis from a received signal on a frequency axis that has been subjected to high resolution processing, and the range is detected.   The average correlation matrix is generated by detecting a predetermined number of targets by converting the pulse-compressed received signal into a time (range) axis signal and performing CFAR (Constant False Alarm Rate) processing. 12. A signal including signals corresponding to an arbitrary number of ranges before and after a target range cell is converted into a frequency axis reception signal, and the plurality of points are extracted to generate a correlation matrix of the frequency axis. A signal processing method for the pulse compression radar apparatus according to the description. In a signal processing method of a pulse compression radar apparatus that repeatedly transmits and receives a plurality of pulses,
The time (range) axis received signal obtained by transmitting and receiving the plurality of pulses is converted into a frequency axis signal in the axial direction of the repetition period of the plurality of pulses,
The received signal converted into the frequency axis is subjected to CFAR (Constant False Alarm Rate) processing to extract a time (range) axis received signal for a frequency bank having an extreme value, and converted into a frequency axis signal;
Generate a reference signal for pulse compression and convert it to a frequency axis signal.
Multiplying the frequency axis reception signal for the frequency bank having the extreme value by the frequency axis reference signal to generate a pulse-compressed reception signal;
A signal of a plurality of points is extracted from the received signal before the pulse compression to generate a frequency axis correlation matrix, the correlation matrix is slid by a plurality of cells, and an average correlation matrix is generated by averaging with a forgetting factor. ,
High-resolution processing of the received signal on the frequency axis with respect to the frequency bank having the extreme value, which is pulse-compressed using the average correlation matrix,
A signal processing method for a pulse compression radar apparatus, in which a target is separated on a time (range) axis from a received signal on a frequency axis that has been subjected to high resolution processing, and the range is detected.   The average correlation matrix is generated by detecting a predetermined number of targets by converting the pulse-compressed received signal into a time (range) axis signal and performing CFAR (Constant False Alarm Rate) processing. 14. A signal including signals corresponding to an arbitrary number of ranges before and after a target range cell is converted into a frequency axis reception signal, the signals at the plurality of points are extracted, and a correlation matrix of the frequency axis is generated. A signal processing method for the pulse compression radar apparatus according to the description. In a signal processing method of a pulse compression radar apparatus that repeatedly transmits and receives a plurality of pulses,
The time (range) axis received signal obtained by transmitting and receiving the plurality of pulses is converted into a frequency axis signal,
Generate a reference signal for pulse compression and convert it to a frequency axis signal.
Multiplying the frequency axis reception signal by the frequency axis reference signal to generate a pulse-compressed reception signal;
A correlation matrix is generated from the pulse-compressed received signal, and an average correlation matrix is generated by averaging the CPI (Coherent Pulse Interval) with a forgetting factor,
High-resolution processing of the pulse-compressed received signal using the average correlation matrix;
A signal processing method of a pulse compression radar apparatus, wherein a target is separated from a received signal subjected to high resolution processing on a time (range) axis and the range is detected.   The average correlation matrix is generated by detecting a predetermined number of targets by converting the pulse-compressed received signal into a time (range) axis signal and performing CFAR (Constant False Alarm Rate) processing. 16. The signal processing method of the pulse compression radar apparatus according to claim 15, wherein a signal corresponding to an arbitrary number of ranges before and after the target range cell is extracted to generate a correlation matrix of the time (range) axis. In a signal processing method of a pulse compression radar apparatus that repeatedly transmits and receives a plurality of pulses,
The time (range) axis received signal obtained by transmitting and receiving the plurality of pulses is converted into a frequency axis signal in the axial direction of the repetition period of the plurality of pulses,
The received signal converted into the frequency axis is subjected to CFAR (Constant False Alarm Rate) processing to extract a time (range) axis received signal for a frequency bank having an extreme value, and converted into a frequency axis signal;
Generate a reference signal for pulse compression and convert it to a frequency axis signal.
Multiplying the frequency axis reception signal for the frequency bank having the extreme value by the frequency axis reference signal to generate a pulse-compressed reception signal;
A correlation matrix is generated from the pulse-compressed received signal, and an average correlation matrix is generated by averaging the CPI (Coherent Pulse Interval) with a forgetting factor,
High-resolution processing of the received signal on the time (range) axis with respect to the frequency bank having the extreme value, which is pulse-compressed using the average correlation matrix,
A signal processing method of a pulse compression radar apparatus that separates a target on the time (range) axis from the received signal on the time (range) axis subjected to the high resolution processing and detects the range.   The average correlation matrix is generated by detecting a predetermined number of targets by converting the pulse-compressed received signal into a time (range) axis signal and performing CFAR (Constant False Alarm Rate) processing. 18. The signal processing method of the pulse compression radar apparatus according to claim 17, wherein a signal corresponding to an arbitrary number of ranges before and after the target range cell is extracted to generate a correlation matrix of the time (range) axis. In a signal processing method of a pulse compression radar apparatus that divides an antenna aperture into two and repeatedly transmits and receives a plurality of pulses by a sum (Σ) beam and a difference (ΔAZ or ΔEL) beam,
A pair of aperture signals is generated from the Σ signal by the sum (Σ) beam and the Δ signal by the difference (ΔAZ or ΔEL) beam,
A phase for directing the beam in a predetermined direction is given by the Σ signal and the Δ signal to form two sum beams, and Σ 1 and Σ 2 signals are generated from the received signals of each beam,
An error voltage based on an amplitude ratio of both signals is calculated by performing the high resolution processing on the frequency axis by performing the processing according to any one of claims 11 to 14 on the Σ1 and Σ2 signals,
A signal processing method of a pulse compression radar apparatus that acquires an angle measurement value from the error voltage. In a signal processing method of a pulse compression radar apparatus that divides an antenna aperture into two and repeatedly transmits and receives a plurality of pulses by a sum (Σ) beam and a difference (ΔAZ or ΔEL) beam,
A pair of aperture signals is generated from the Σ signal by the sum (Σ) beam and the Δ signal by the difference (ΔAZ or ΔEL) beam,
A phase for directing the beam in a predetermined direction is given by the Σ signal and the Δ signal to form two sum beams, and Σ 1 and Σ 2 signals are generated from the received signals of each beam,
An error voltage due to an amplitude ratio of both signals is calculated by performing the processing according to any one of claims 15 to 18 on the Σ1 and Σ2 signals and performing high resolution processing on a time axis,
A signal processing method of a pulse compression radar apparatus that acquires an angle measurement value from the error voltage.

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