JP4655759B2 - Data compression apparatus, reproduction method and pulse compression radar apparatus for pulse compression radar - Google Patents

Description

  The present invention relates to a data compression apparatus for pulse compression radar, a reproduction method, and a pulse compression radar apparatus, and more particularly to a data reproduction apparatus and reproduction applied to data reproduction for a real-type pulse compression radar apparatus that performs IQ separation after A / D conversion. The present invention relates to a method and a pulse compression radar apparatus.

  Pulse compression radar equipment, including SAR (Synthetic Aperture Radar) mounted on artificial satellites for earth exploration, has come to be widely used as a radar system that acquires high-resolution remote sensing performance. Yes. In this pulse compression radar apparatus, as shown in FIG. 6, the pulse power is suppressed with respect to the received data of the reflected wave reflected from the target by suppressing the peak power using a transmission wave having a long pulse width subjected to frequency modulation. By performing the processing, a reception wave having a narrow pulse width is obtained equivalently to achieve high resolution. FIG. 6 is a pulse waveform diagram for explaining the basic operation principle of a general data compression apparatus for pulse compression radar.

  When performing pulse compression on the received data, the received signal is sampled by A / D conversion. As shown in FIG. 7, the signal is separated into an I signal and a Q signal, respectively. There are an IQ system that performs A / D conversion on the above signals and a real system that performs A / D conversion without separating the signals into IQ, as shown in FIG. FIG. 7 is a block diagram showing the configuration of a conventional pulse compression radar data reproducing apparatus using the IQ method, and FIG. 8 is a block diagram showing the structure of a conventional pulse compressing radar data reproducing device using the real method. It is a block diagram.

  In the case of the former IQ-system pulse compression radar data reproducing device shown in FIG. 7, the received wave received from the antenna 51 as disclosed in JP 2002-82162 A “pulse compression radar device” shown in Patent Document 1, The frequency conversion circuit 521 of the receiver 52 performs frequency conversion with the Local signal, and generates a virtual image signal at the position of the center frequency −fc having the opposite sign of the reception signal of the center frequency fc and the center frequency fc, and IQ separation. Input to the circuit 53. In the IQ separation circuit 53, the phase detection of the Q signal is performed by phase-shifting the COHO signal (Coherent Oscillator) for phase detection of the I signal and the COHO signal by 90 degrees by the phase shifter 531. After being detected by each signal, only desired signal components are output as I and Q signals via filters 533a and 533b, and are sampled by clock signals (CLK) by A / D converters 54a and 54b, respectively. Processing is performed and output to pulse compression processing.

  On the other hand, unlike the case of the IQ method, the latter real method pulse compression radar data reproducing apparatus shown in FIG. 8 does not include an IQ separation circuit for IQ separation in the preceding stage of the A / D converter 64. The received wave received from the antenna 61 is frequency-converted by the local signal in the frequency conversion circuit 621 of the receiver 62 to generate a real signal having the center frequency fc and a virtual image signal having the opposite center frequency −fc. The A / D converter 64 performs sampling processing with the clock signal (CLK) without separating the I signal and Q signal via the filter 63, and outputs the result to the pulse compression processing.

  Therefore, in the case of a real-type pulse compression radar data reproducing apparatus, in order to make the sampling rate variable according to the bandwidth of the transmission wave, as shown in FIG. After the (A / D conversion process), a process for digitally performing IQ separation is required. FIG. 9 is a block diagram showing a realistic configuration of a conventional real-type pulse compression radar data reproducing apparatus. As shown in FIG. 9, a signal sampled by a clock signal (CLK: frequency 4 · fc) four times the center frequency fc by the A / D converter 64 is input to the digital IQ separation circuit 65 and I The signal and Q signal are separated, and further, each signal is thinned out to (1 / n) according to the signal bandwidth by the thinning processing circuit 66 (n: positive integer of 1 or more), and pulse compression is performed. It is necessary to output to processing. Thus, for the first time, the sampling frequency can be made variable according to the bandwidth of the transmission wave.

JP 2002-82162 A (page 4, FIG. 1)

  However, in the case of a real-type pulse compression radar data reproduction device, the center frequency of the received signal is shifted from fc to 0 Hz in the IQ separation process of the digital IQ separation circuit 65. At this time, a virtual image signal (what is a real signal? The same frequency (from -fc to -2 fcHz) is also shifted with respect to the signal having the opposite negative frequency -fc. Therefore, the digital IQ separation circuit 65 needs to use a digital filter in order to erase this virtual image signal, and there is a problem that the circuit scale increases. A detailed configuration of the conventional digital IQ separation circuit 65 is shown in FIG.

  FIG. 10 is a block configuration diagram showing an internal configuration of the digital IQ separation circuit 65 of the data compression apparatus for pulse compression radar shown in FIG. As shown in FIG. 10, the received signal (the real signal of the center frequency fc and the virtual image signal of the center frequency −fc) input to the digital IQ separation circuit 65 is a demultiplexer of 4ch (a band four times the center frequency fc). (DMUX) 651 separates the I signal and the Q signal, and the sign inversion circuits 652a and 652b invert the signs of the respective signals in order to provide 2ch (double the center frequency fc) multiplexers. (MUX) Output to digital filters 654a and 654b via 653a and 653b.

  Since the I and Q signals input to the digital filters 654a and 654b are accompanied by virtual image signals having frequencies of 2fc and -2fc in addition to the real signal shifted to 0 Hz, the digital filters 654a and 654b A virtual image signal having a frequency of 2fc and -2fc is filtered, and only an I signal and a Q signal shifted to 0 Hz are output.

  Thus, in the process of performing IQ separation after A / D conversion, it is necessary to use a digital filter, and an increase in circuit scale is inevitable. In other words, as shown in FIG. 10, the conventional real data compression apparatus for pulse compression radar requires digital filters 654a and 654b after digitally separating the I and Q signals, resulting in a large circuit scale. There was a problem of becoming. Accordingly, an object of the present invention is to make it possible to reduce the circuit scale by devising a method that does not use a digital filter in a real-type pulse compression radar data recovery device.

  In order to solve the above-described problems, the data compression apparatus, the reproduction method, and the pulse compression radar apparatus according to the present invention employ the following characteristic configuration.

(1) Real-type pulse compression radar data that is digitally separated into an I signal and a Q signal after A / D conversion is performed on a radar reception signal indicating a received pulse-compressed radar transmission signal. In the playback device,
After digital IQ separation processing, a data processing unit including at least a thinning processing unit that performs digital thinning processing according to the bandwidth of the radar transmission signal, and zero padding that means no data in the thinned data portion A pulse including at least a zero padding processing unit that performs processing and a correlation processing unit that performs pulse compression of a signal component from which a virtual image signal has been removed by correlation processing using a reference function on a frequency axis after FFT (Fast Fourier Transform) processing A data compression apparatus for pulse compression radar comprising a compression processing unit.
(2) The pulse compression radar data reproducing apparatus according to (1), wherein the thinning processing unit decreases the thinning rate as the bandwidth of the radar transmission signal increases.
(3) The above-described zero padding processing unit further performs a zero padding process that means that no data is provided to a vacant data portion by alternately shifting the I signal and the Q signal in time. (2) A data reproducing apparatus for pulse compression radar.
(4) In digital IQ separation processing, sample data after A / D conversion is separated into an I signal and a Q signal while inverting the plus, minus sign and minus, plus sign in order. The data reproduction apparatus for pulse compression radar according to any one of (1) to (3), wherein the processing is repeated in units of a magnification of the sampling rate of A / D conversion with respect to the center frequency of the received signal.
(5) The data reproduction apparatus for pulse compression radar according to (4), wherein the reference function used in the correlation processing unit is composed of a component having a frequency characteristic opposite to the signal component.
(6) In digital IQ separation processing, sample data after A / D conversion is separated into an I signal and a Q signal while inverting the minus and plus signs and the plus and minus signs respectively. The data reproduction apparatus for pulse compression radar according to any one of (1) to (3), wherein the processing is repeated in units of a magnification of the sampling rate of A / D conversion with respect to the center frequency of the received signal.
(7) The data reproducing apparatus for pulse compression radar according to (6), wherein the reference function used in the correlation processing unit is composed of a component having the same frequency characteristic as a signal component.
(8) The pulse compression radar data reproducing apparatus according to any one of (1) to (7), wherein the processing performed by the pulse compression processing unit is realized as program logic executable by a computer.
(9) In a pulse compression radar apparatus including a transmission unit that transmits a frequency-modulated pulse signal toward a target, and a reception unit that performs reception processing by performing pulse compression processing on the radar reception signal. A pulse compression radar device using the pulse compression radar data reproduction device according to any one of (1) to (8) above.
(10) In a pulse compression radar apparatus having a transmission unit that transmits a frequency-modulated pulse signal toward a target and a reception unit that performs reception processing of the radar reception signal, the pulse compression processing unit as the data reproduction device At least the data processing unit of any one of the above (1) to (8) is mounted as the receiving unit by inputting the received sampling data, and the thinning process of the data processing unit A pulse compression radar device that transmits data thinned out from a part as sampling data for pulse compression processing to the outside.
(11) Among the data processing unit and the pulse compression processing unit, at least the pulse compression processing unit is mounted, and data thinned out from the thinning processing unit input to the pulse compression processing unit is converted to an external pulse The pulse compression radar apparatus according to any one of (1) to (8), which can be received from the compression radar apparatus.
(12) Digital IQ separation in a real-type pulse compression radar data reproduction method for digitally separating an I signal and a Q signal after A / D conversion is performed on the received radar received signal After processing, digital thinning processing according to the bandwidth of the signal and zero padding processing that means no data is performed on the thinned data portion, and referred to on the frequency axis after FFT (Fast Fourier Transform) processing A data compression method for pulse compression radar that performs pulse compression of a signal component from which a virtual image signal is removed by correlation processing using a function.
(13) In the zero padding process, the pulse of the above (9) is further applied to the empty data portion by shifting the I signal and the Q signal alternately in time, which means that there is no data. Data reproduction method for compression radar.
(14) In digital IQ separation processing, the sample data after A / D conversion is separated into an I signal and a Q signal while inverting the plus, minus sign and minus, plus sign in order. The data reproduction method for pulse compression radar as described in (12) or (13) above, wherein the processing is repeated in units of the magnification of the sampling rate of A / D conversion with respect to the center frequency of the received signal.
(15) The data reproduction method for pulse compression radar according to (14), wherein the reference function used in the correlation processing includes a component having a frequency characteristic opposite to a signal component.
(16) In digital IQ separation processing, sample data after A / D conversion is separated into an I signal and a Q signal while inverting the minus and plus signs and the plus and minus signs respectively. The data compression method for pulse compression radar as described in (12) or (13) above, wherein the processing is repeated in units of the magnification of the sampling rate of A / D conversion with respect to the center frequency of the received signal.
(17) The data compression method for pulse compression radar according to (16), wherein the reference function used in the correlation processing is composed of a component having the same frequency characteristic as a signal component.

  According to the data compression apparatus, the reproduction method, and the pulse compression radar apparatus according to the present invention, it is not necessary to use a digital filter even when used for a real type pulse compression radar. There is an effect.

  In general, in the case of a data compression apparatus for a pulse compression radar of a real system, it is necessary to perform IQ separation after A / D conversion in order to make the sampling rate variable according to the bandwidth of the transmission wave. In the conventional configuration, it is necessary to use a digital filter in order to erase the virtual image signal. However, the pulse compression radar data reproduction device, the pulse compression radar data reproduction method, and the pulse compression radar device according to the present invention are configured to eliminate the need for a digital filter in the process of IQ separation. The size and weight can be reduced, and the sampling rate can be varied according to the bandwidth of the target signal, so that the amount of output data can be easily reduced.

  The reason is that in the present invention, since a digital filter is not used in the process of IQ separation, a virtual image signal remains in the signal after IQ separation, and the signal after IQ separation is subjected to thinning processing as it is. The real signal and the virtual image signal overlap on the frequency axis. In the stage of the pulse compression process, by performing zero padding processing, the real signal and the virtual image signal are separated on the frequency axis, and FFT ( This is because the correlation processing using the reference function is performed on the frequency axis after the Fast Fourier Transform) process, the virtual image signal is removed by the matched filter, and the pulse compression is performed only on the signal component.

  Preferred embodiments of a pulse compression radar data reproduction apparatus, a pulse compression radar data reproduction method, and a pulse compression radar apparatus according to the present invention will be described below with reference to the accompanying drawings.

  The present invention relates to a real-type pulse compression radar data reproduction device, a pulse compression radar data reproduction method, and a pulse compression radar device that digitally perform IQ separation after A / D conversion is performed on a received wave. Thus, it is possible to reduce the size and weight of the circuit without using a digital filter after IQ separation, and easily reduce the sampling rate (data amount) according to the bandwidth of the target signal. A pulse compression radar data reproduction device, a pulse compression radar data reproduction method, and a pulse compression radar device are provided.

(Configuration of Example)
FIG. 1 is a block diagram showing an example of a schematic configuration of a data compression apparatus for pulse compression radar according to the present invention. A data compression apparatus 10 for pulse compression radar shown in FIG. 1 includes at least an antenna 1, a receiver 2, a data processing unit 3, and a pulse compression processing unit 4.

  The antenna 1 and the receiver 2 have a general configuration in the reception system of the pulse compression radar apparatus, and are exactly the same as the conventional configuration shown in FIGS. The received wave received from the antenna 1 is frequency-converted by the local signal in the frequency conversion circuit 21 of the receiver 2, and the received signal of the center frequency fc and the center frequency fc are at the position of the center frequency −fc of the opposite sign. A virtual image signal is generated and input to the data processing unit 3.

  In the data processing unit 3, A / D conversion in the A / D converter 32, IQ separation in the digital IQ separation circuit 33, thinning out in the thinning processing circuit 34, and the like are performed, and sampling data 34A is input to the pulse compression processing unit 4. Is output. The sampling data 34A is processed by the pulse compression processing unit 4 with zero padding in the zero padding processing block 41, FFT (Fast Fourier Transform) processing in the FFT block 42, virtual image signal removal and pulse compression processing in the correlation processing block 43, and inverse FFT block 44. At least processing such as inverse FFT conversion is performed and reproduced as a pulse compression result 44A.

  Here, the data processing unit 3 applies band limitation to the analog signal having the center frequency fc input from the receiver 2 and outputs the filtering signal 31A, and the band-limited filtering signal 31A. A / D converter 32 that performs A / D conversion by sampling at a CLK signal of 4 times the center frequency fc (4 · fc), and separates the A / D converted data into an I signal and a Q signal The digital IQ separation circuit 33 that is output as the IQ separation signal 33A, and the sampling rate is made variable in accordance with the bandwidth of the transmission signal, so that (1 / n) data (n: positive integer of 1 or more) is thinned out. And at least a decimation processing circuit 34 that outputs the sampling data 34A for pulse compression processing. Although the filter 31 is included in the data processing unit 3, the filter 31 may be included on the receiver 2 side.

  Among these, the digital IQ separation circuit 33 includes at least a DMUX 331, sign inversion circuits 332a and 332b, MUX 333a and 333b, as shown in FIG. 2, and the conventional digital IQ separation circuit 65 shown in FIG. In this configuration, the digital filters 654a and 654b are deleted. FIG. 2 is a block configuration diagram showing an example of the internal configuration of the digital IQ separation circuit 33 of the data compression apparatus 10 for pulse compression radar shown in FIG.

  In the digital IQ separation circuit 33, each sample s0, s1, s2, s3, s4, s5, s6,... Of the sample signal 32A which is A / D converted at a four times speed and output from the A / D converter 32 is obtained. The DMUX 331 sets four samples as one unit, the first sample s0 is the first I signal from the MUX 333a, and the second sample s1 is subjected to the sign inversion by the sign inversion circuit 332b, and the QUX signal from the MUX 333b As the first, the third sample s2 is subjected to the sign inversion by the sign inversion circuit 332a, the second I signal from the MUX 333a, the fourth sample s3 as the second Q signal from the MUX 333b, and so on. The processing is repeated to perform demultiplexing processing, and the I signals s0, -s2, s4, -s6, s8, ... and the Q signals -s1, s3,- are separated into s5, s7, -s9,... and output as an IQ separation signal 33A to the thinning processing circuit.

  The pulse compression processing unit 4 includes at least a zero padding processing block 41, an FFT block 42, a correlation processing block 43, and an inverse FFT block 44. In the pulse compression processing unit 4, the sampling data 34 </ b> A thinned out to (1 / n) according to the bandwidth by the thinning processing circuit 34 in the data processing unit 3 is padded with zeros in the zero padding processing block 41. The zero padded data 41A is output to the FFT block 42.

  Further, the result obtained by performing the FFT process in the FFT block 42 and converting it to the data on the frequency axis is multiplied by the reference wave (reference function) 43B from the reference function block 432 in the correlation processing block 43. By performing this in the unit 431, pulse compression processing is performed only on the signal component from which the virtual image signal component has been removed, and the correlation processing data 43A is output to the inverse FFT block 44. By performing inverse FFT processing in the inverse FFT block 44, the data on the frequency axis is returned to the original data on the time axis, and output as a pulse compression result 44A. The correlation processing block 43 functions as a matched filter by the reference wave (reference function) 43B from the reference function block 432, and the reference wave (reference function) 43B has a signal band component having a frequency characteristic opposite to that of the signal. Is a signal wave.

  The pulse compression processing unit 4 may be realized by a program logic executable by a computer as software processing by an on-board real-time processing device. Furthermore, the pulse compression processing unit 4 may be configured as a device separate from the data processing unit 3 instead of being integrated with the data processing unit 3 as the data compression device 10 for pulse compression radar. For example, a pulse compression radar device mounted on an artificial satellite or an aircraft is configured not to include the pulse compression processing unit 4 but to include at least the data processing unit 3, and outputs from the thinning processing circuit 34 of the data processing unit 3. The pulse compression radar configured to include at least the pulse compression processing unit 4 by transmitting the thinned data, that is, the sampling data 34A to the outside (for example, toward the ground) as the sampling data for pulse compression processing by some means. The data reproduction apparatus 10 may receive the pulse compression processing sampling data transmitted and input the pulse compression processing unit 4 to calculate and output the pulse compression result 44. In this case, the pulse compression radar data reproduction device 10 is realized by a ground processing device separate from the equipment on which the data processing unit 3 is mounted.

  Although FIG. 1 omits the description of the configuration of the radar signal transmission system, it may be integrated with the transmission system and configured as a pulse compression radar device, or may be configured separately. It does not matter either. When configured as a pulse compression radar device integrated with a transmission system, a transmission unit that transmits a pulse signal frequency-modulated based on a chirp signal coefficient toward a target as a transmission signal, and a reception wave that is a reflected pulse thereof And a reception unit that performs reception processing by performing pulse compression processing based on a pulse compression coefficient, and a data recovery device for pulse compression radar as shown in this embodiment is used for the reception unit. It ’s fine.

(Description of operation of the embodiment)
Next, an example of the operation of the data compression apparatus 10 for pulse compression radar according to the present embodiment shown in FIGS. 1 and 2 will be described with reference to FIGS. As described above, the reflected wave of the transmission signal transmitted from the pulse compression radar device toward the target is received by the antenna 1, down-converted by the frequency conversion circuit 21 of the receiver 2, and converted to the center frequency fc. Is done. The operation so far is exactly the same as that of the conventional pulse compression radar data reproducing apparatus shown in FIGS.

  The output signal from the receiver 2 is input to the data processing unit 3, the band is limited only to the bandwidth required as the bandwidth of the received signal by the analog filter 31, and is output as the filtered signal 31 </ b> A. When switching the band of the transmission signal, by switching the filtering coefficient of the filter 31, only the signal in the desired band after the switching is passed, and the passage restriction is performed on the signal outside the band. Thereby, the filtering signal 31A output from the filter 31 is limited to a signal having a bandwidth centered on the center frequency fc. However, at this stage, as shown in the spectrum of FIG. There is a virtual image signal centered on a negative frequency −fc of the opposite sign.

  Thereafter, the filtering signal 31A output from the filter 31 is sampled into digital data at an A / D conversion speed four times the center frequency fc in the A / D converter 32, and is output as a sample signal 32A. The spectrum of the sample signal 32A is folded back as a signal in the frequency range of (-2fc to + 2fc) as shown in FIG. Here, the frequency of the real signal of the sample signal 32A has a bandwidth centered on + fc, while the virtual image signal has a bandwidth centered on -fc.

  The sample signal 32A output from the A / D converter 32 is subsequently input to the digital IQ separation circuit 33. As described above, the sample signal 32A input to the digital IQ separation circuit 33 is sequentially separated into an I signal and a Q signal with 4 samples as one unit.

  In the digital IQ separation circuit 33, the first sample s0 of the input sample signal 32A is directly subjected to the sign inversion of the first and second samples s1 of the I signal, and the first and third samples s2 of the Q signal are obtained. The sign is inverted, and the second and fourth samples s3 of the I signal are output as they are as the second signal of the Q signal. That is, if the data string of the input sample signal 32A is s0, s1, s2, s3, s4, s5, s6, as shown in FIG. 2, the output on the I signal side is s0, -s2, s4. , −s6, s8,..., And the output on the Q signal side is an IQ separation signal 33A composed of data strings of −s1, s3, −s5, s7, −s9,.

  The sign inversion here is sign inversion corresponding to the voltage of the signal. As shown in FIG. 2, the spectrum of the IQ separation signal 33A is frequency-converted to the minus side by fc and has a band centered on 0 Hz. On the other hand, the virtual image signal is similarly frequency-converted to the minus side by fc. However, since it is a folded spectrum in the range of (−2fc to + 2fc), half of the virtual image signal appears on the −2fc side and the other half appears on the + 2fc side.

  The IQ separation signal 33A output from the digital IQ separation circuit 33 is subsequently input to the thinning processing circuit 34 in order to make the sampling rate variable according to the bandwidth. In the thinning processing circuit 34, as shown in FIG. 3, the I signal and the Q signal are combined into one set, and thinning is performed to 1 / n (n is a positive integer of 1 or more that gives a thinning rate). FIG. 3 is a schematic diagram showing an example of the thinning process 34 of the pulse compression radar data reproducing apparatus 10 shown in FIG. 1 and the zero padding process of the zero padding processing block 41.

  In FIG. 3, for example, when the thinning rate n is 2 (that is, in the case of 1/2 thinning), the sampling data 34A output after the thinning is the first s0 of the I signal and the first -s1 of the Q signal. Then, the second -s2 of the I signal and the second s3 of the Q signal are thinned out, the third s4 of the I signal and the third -s5 of the Q signal are output, and the third s4 of the I signal. Next to the third -s5 of the Q signal, the fourth -s6 of the I signal and the fourth s7 of the Q signal are thinned out, and the fifth s8 of the I signal and the fifth -s9 of the Q signal are output. Is done.

  Further, when the thinning rate n is 3 (that is, in the case of 1/3 thinning), the sampling data 34A output after the thinning is as follows after the first s0 of the I signal and the first -s1 of the Q signal: The second -s2 and third s4 of the I signal and the second s3 and third -s5 of the Q signal are thinned out, and the fourth -s6 of the I signal and the fourth s7 of the Q signal are output. In addition, when the thinning rate n is 4 (that is, in the case of 1/4 thinning), the sampling data 34A output after the thinning is as follows after the first s0 of the I signal and the first -s1 of the Q signal: The second s2, the third s4 and the fourth s6 of the I signal and the second s3, the third s5 and the fourth s7 of the Q signal are thinned out, and the fifth s8 of the I signal and the fifth of the Q signal -S9 is output.

Here, the thinning-out rate n of the thinning-out processing circuit 34 is represented by the sampling theorem when the signal bandwidth is B and the A / D conversion speed is fs (= 4fc).
n <fs / B
To satisfy. As shown in FIG. 3, the sampling data 34A output from the thinning-out processing circuit 34 is spectrally viewed when the thinning-out rate n is 2 or more (−2fc) when the thinning-out rate n is 2 or more. ˜ + 2fc) to the following bands. That is, when the thinning rate n is 2, (−fc to + fc), when the thinning rate n is 3, (−2fc / 3 to + 2fc / 3), when the thinning rate n is 4, (−fc) / 2 to + fc / 2), and as a result, the signal band and the virtual image signal band in the frequency 0 region except for the case of no thinning (thinning rate n = 1). Will overlap.

  Subsequently, output data of the thinning processing circuit 34, that is, sampling data 34 </ b> A is input to the pulse compression processing unit 4. In the pulse compression processing unit 4, first, the zero padding processing block 41 performs zero padding of the sampling data 34 </ b> A thinned out by the thinning processing circuit 34. In the zero padding processing block 41, first, as shown in FIG. 3, zeros are padded to blank portions generated by alternately shifting the I signal and the Q signal, and subsequently, the sample portion thinned out by the thinning processing circuit 34 is added. Also stuffs zero.

  For example, when the thinning rate n is 1 (that is, 1/1 thinning without thinning), the first output data of the I signal is the first s0 of the input data of the I signal, the second is padded with 0, and the third Is the second -s2 of the input data, the fourth is zero-padded, the fifth is the third s4 of the input data, the sixth is zero-padded, and so on, while the first output data of the Q signal is zero-padded, second Is the 1st -s1, the 3rd is 0 padded, the 4th is the 2nd s3 of the input data, the 5th is the 0 padded, the 6th is the 3rd -s5 of the input data, and so on. Data 41A is output.

  When the thinning rate n is 2 (that is, 1/2 thinning), the first output data of the I signal is the first s0 of the input data of the I signal, the second to fourth are padded with zeros, and the fifth is the input. The third s4, 6-8th of the data is zero-padded, the ninth is the fifth s8 of the input data, the 10-12th is zero-padded,..., While the first of the output data of the Q signal is zero-padded, 2 The first is the first -s1 of the input data of the Q signal, the third to fifth are zero-padded, the sixth is the third -s5 of the input data, the seventh to ninth are zero-padded, and the tenth is the fifth of the input data-s9. ,... Are output as zero padded data 41A.

  The same applies to the case where the thinning rate n is 3 or more. When the thinning rate n is 3 (that is, in the case of 1/3 thinning), the first output data of the I signal is the first s0 of the input data of the I signal. 2nd to 6th are 0 padded, 7th is input data 4th-s6, 8th to 12th are padded to 0, 13th is input data 7th s12, 14th to 18th are padded to 0, etc. The first output data of the Q signal is zero-padded, the second is the first -s1 of the Q-signal input data, the third to seventh are zero-padded, the eighth is the fourth s7 of the input data, and the ninth to thirteenth are Zero-padded, 14th-input data 7A-s13,... 0-padded data 41A is output.

  When the thinning rate n is 4 (that is, 1/4 thinning), the first output data of the I signal is the first s0 of the input data of the I signal, the second to eighth are padded with 0, and the ninth is the input. The fifth s8, 10th to 16th of the data are 0-padded, the 17th is the 9th s16 of the input data, the 18th to 24th are 0-padded,..., While the first output data of the Q signal is 0-padded, 2 The first is the first -s1 of the input data of the Q signal, the third to ninth are 0-padded, the fifth is the fifth -s9 of the input data, the 11th to 17th are zero-padded, and the 18th is the ninth of the input data-s17. ,... Are output as zero padded data 41A.

  Here, “0” in the zero padding process does not necessarily mean 0 as a code value, but means that there is no data in which the signal amplitude is 0 V level, that is, the ± middle point. Thus, in terms of spectrum, as shown in FIG. 3, the sampling data 34A output from the thinning processing circuit 34 has a frequency of 0 as described above, except when there is no thinning (thinning rate n = 1). In the area, the signal band and the virtual image signal band overlap, but the zero-padded data 41A output from the zero-padded processing block 41 subjected to the zero padding process has no thinning even when the thinning rate n is 2 or more ( As in the case of the thinning rate n = 1), the bandwidth returns to (-2fc to + 2fc), and the signal band and the virtual image signal band are completely separated.

  The zero-padded data 41A output from the zero-padded processing block 41 is subjected to FFT processing in the FFT block 42, and data on the time axis is converted into data on the frequency axis. Thereafter, in the correlation processing block 43, the multiplier 431 performs multiplication processing with the reference wave 43B from the reference function block 432. Here, the reference wave 43B is a signal wave represented by a reference function having a frequency characteristic opposite to that of a signal transmitted for radar and having only a signal band component.

  As a result, the matched filter processing by the reference function is performed, the pulse compression is performed, and at the same time, the virtual image signal is removed as shown in the spectrum of the correlation processing data 43A in FIG. Thereafter, by performing inverse FFT processing in the inverse FFT block 44, the data on the frequency axis is returned to the data on the time axis, and is output as a pulse compression result 44A as shown in the compressed pulse waveform of FIG. The

  In addition, the example which illustrated the above process with another expression method is shown in FIG. FIG. 4 is a schematic diagram showing an example of expression different from FIG. 3 of the thinning process 34 of the pulse compression radar data reproducing apparatus 10 shown in FIG. 1 and the zero padding process of the zero padding processing block 41. Data (sample signal 32A) sampled at a speed 4fc that is four times the center frequency fc in the A / D converter 32 is a signal (I signal: 1, 0, -1, 0) of the frequency fc in the digital IQ separation circuit 33a. , 1, 0, −1, 0,..., Q signals: 0, −1, 0, 1, 0, −1, 0, 1,. Is done.

  Thereafter, in the thinning processing circuit 34a, the frequency is mixed with the thinned signal 34B of 0, ± fc (2 / n), ± fc (4 / n),..., ± fc (2 (n−1) / n). Thus, a thinning process is performed and output as sampling data 34A. Note that in the sampling data 34A shown in FIG. 4, both the blank data portion generated by alternately shifting the I signal and the Q signal in time and the thinned sample data portion are filled with “0”. However, the actual data output to the subsequent zero padding processing block 41a is only the data of the shaded portion that is not expressed as “0”. After the thinning process in the thinning processing circuit 34a, the zero padding process block 41a performs the zero padding process on the portion displayed as “0” in the sampling data 34A of FIG. 4 and outputs it as the zero padding data 41A. The

  The subsequent processing is the same as in FIG. 3, and the virtual image signal is removed by performing the FFT processing in the FFT block 42, the correlation processing with the reference function in the correlation processing block 43, and the inverse FFT processing in the inverse FFT block 44. And the signal component are subjected to pulse compression processing and output as a pulse compression result 44A.

(Explanation of effect)
In the case of a real-type pulse compression radar data recovery device, IQ separation needs to be performed after A / D conversion in order to make the sampling rate variable according to the bandwidth of the transmission wave. In the IQ separation process, it was necessary to use a digital filter to erase the virtual image signal. However, since the data reproduction method of the present invention does not require a digital filter in the IQ separation process as described above, the circuit can be reduced in size and weight, and the sampling speed (data amount) can be set to the target signal. The effect that it can reduce easily according to the bandwidth of this can be produced.

(Another embodiment of the present invention)
In the embodiment of the data compression apparatus 10 for pulse compression radar shown in FIG. 1, the data processing function after the thinning processing circuit 34 is omitted in the data processing unit 3 of FIG. An additional circuit may be attached.

  Further, the digital IQ separation circuit 33 shown in the embodiment of FIG. 2 is changed in its configuration as shown in the digital IQ separation circuit 33b of FIG. 5, and the insertion positions of the sign inversion circuits 332a and 332b into the DMUX 331 are changed. They may be changed from the third to the first and from the second to the fourth, respectively. FIG. 5 is a block diagram showing a processing example different from that in FIG. 1 of the IQ separation processing circuit of the data compression apparatus for pulse compression radar according to the present invention.

  In the case of the digital IQ separation circuit 33b in FIG. 5, the order of sign inversion is changed from that of the IQ separation signal 33A in the digital IQ separation circuit 33 in FIG. 2, and s0, -s2, s4, -s6, s8,. To -s0, s2, -s4, s6, -s8, ..., and for the Q signal, -s1, s3, -s5, s7, -s9, ... to s1, -s3, s5, -s7, s9, ... Since they are interchanged, it is the same even if the virtual image signal is treated as a signal instead of the original signal. In this case, since the frequency characteristics are inverted, the reference function in the correlation processing block 43 in the subsequent stage is different from the reference wave 43B shown in FIG. It is necessary to change so as to have the same frequency characteristic as that of the signal.

  In the embodiment of FIG. 1, the output signal of the receiver 2 has fc as the center frequency, but is set to (fc + 4fc × integer multiple) in consideration of aliasing due to sampling in the A / D converter 32. Is basically the same. When the virtual image signal is handled as a signal, it is basically the same if the center frequency is set to (fc + 2fc + 4fc × integer multiple) instead of (fc + 2fc) by shifting by 2fc.

  Further, the pulse compression processing unit 4 of the embodiment of FIG. 1 is the same even if additional processing such as look division processing is further added in order to obtain higher performance resolution. It is also possible to add a synthetic aperture processing or the like after the pulse compression processing and apply it as a synthetic aperture radar device.

  In the embodiment of FIG. 1, thinning is performed after the IQ separation processing circuit 33. However, if the output data is the same, the same is true even if the order of both circuits is reversed. is there. Further, the same is true if IQ separation is performed not by the data processing unit 3 but by the pulse compression processing unit 4.

  As will be described repeatedly, in the pulse compression radar data reproduction apparatus, the pulse compression radar data reproduction method, and the pulse compression radar apparatus according to the present invention, as illustrated in FIG. 1, a digital IQ separation circuit that does not use a digital filter. 33 is used, the virtual image signal remains in the IQ separation signal 33A output from the digital IQ separation circuit 33. If the IQ separation signal 33A after the IQ separation is directly subjected to the thinning process according to the signal bandwidth, the signal and the virtual image signal overlap each other on the frequency axis as shown as sampling data 34A. For this reason, by performing zero padding processing at the stage of pulse compression processing, it becomes possible to separate the signal and the virtual image signal on the frequency axis as shown as zero padding data 41A. Thereafter, after FFT processing, correlation processing using a reference function on the frequency axis is performed, whereby the virtual image signal can be removed by the matched filter and pulse compression of only the signal component can be performed.

  The configuration of the preferred embodiment of the present invention has been described above. However, it should be noted that such examples are merely illustrative of the invention and do not limit the invention in any way. Those skilled in the art will readily understand that various modifications and changes can be made according to a specific application without departing from the gist of the present invention.

It is a block block diagram which shows an example of schematic structure of the data reproduction apparatus for pulse compression radar by this invention. FIG. 2 is a block configuration diagram illustrating an example of an internal configuration of a digital IQ separation circuit of the pulse compression radar data reproduction device illustrated in FIG. 1. FIG. 3 is a schematic diagram illustrating an example of a thinning process circuit of the pulse compression radar data reproduction device illustrated in FIG. 1 and a zero padding process of a zero padding process circuit. FIG. 4 is a schematic diagram illustrating an expression example different from FIG. 3 of the thinning-out processing circuit of the pulse compression radar data reproducing device illustrated in FIG. 1 and the zero-packing processing of the zero-packing processing circuit. It is the block block diagram which showed the process example different from FIG. 1 of the IQ isolation | separation processing circuit of the data reproduction apparatus for pulse compression radar by this invention. It is a pulse waveform diagram for demonstrating the basic operation | movement principle of the data reproduction apparatus for general pulse compression radars. It is a block block diagram which shows the structure of the data reproduction apparatus for pulse compression radars by the conventional IQ system. It is a block block diagram which shows the structure of the data reproduction apparatus for pulse compression radars by the conventional real system. It is a block block diagram which shows the realistic structure in the conventional data reproduction apparatus for pulse compression radars of a real system. It is a block block diagram which shows the internal structure of the digital IQ separation circuit of the data reproduction apparatus for pulse compression radar shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna 10 Data reproduction | regeneration apparatus for pulse compression radar 2 Receiver 21 Frequency conversion circuit 3 Data processing part 31 Filter 31A Filtering signal 32 A / D converter 32A Sample signal 33 Digital IQ separation circuit 331 DMUX
332a, 332b Sign inversion circuit 333a, 333b MUX
33A IQ separation signals 33a, 33b Digital IQ separation circuit 34 Thinning processing circuit 34A Sampling data 34a Thinning processing circuit 4 Pulse compression processing unit 41 0 padding processing block 41A 0 padding data 41a 0 padding processing block 42 FFT block 43 Correlation processing block 431 Multiplication 432 Reference function block 43A Correlation processing data 43B Reference wave 44 Inverse FFT block 44A Pulse compression result 51 Antenna 52 Receiver 521 Frequency conversion circuit 53 IQ separation circuit 531 Phase shifters 532a and 532b Detectors 533a and 533b Filters 54a and 54b A / D converter 61 Antenna 62 Receiver 621 Frequency conversion circuit 63 Filter 64 A / D converter 65 Digital IQ separation circuit 651 Demultiplexer (DMUX)
652a, 652b Sign inversion circuit 653a, 653b Multiplexer (MUX)
654a, 654b digital filter 66 thinning processing circuit

Claims (16)

Down-converts the received radar signal indicating the pulse-compressed radar transmission signal, converts the frequency to the center frequency, and filters the received frequency-converted radar reception signal to obtain a bandwidth signal centered on the center frequency. And the frequency of the filtered signal is A / D converted at an A / D conversion speed four times the center frequency, and then separated into an I signal and a Q signal. In the data recovery device for pulse compression radar,
After I Q separation, n <fs / B (where thinning rate n, the bandwidth B, and the A / D conversion speed and fs) so as to satisfy the, to the IQ separation processing signals A data processing unit including at least a thinning-out processing unit that performs a thinning-out processing, a zero-packing processing unit that performs zero-padding processing that indicates no data for the thinned-out data portion, and data that has been subjected to zero-padding processing is represented by FFT (Fast A pulse compression process including at least a correlation processing unit that performs pulse compression of a signal component obtained by removing a virtual image signal by a correlation process using a reference function with respect to a result obtained by performing a Fourier transform process and converting the data into a frequency axis data A data compression apparatus for pulse compression radar, characterized by comprising a unit. The zero padding processing unit performs zero padding processing that means that there is no data even for the empty data portion by alternately shifting the output order of the I signal and Q signal subjected to the thinning processing in time. The data reproduction apparatus for pulse compression radar according to claim 1. In I Q separation process, the sample data after A / D conversion, plus, minus and minus, while reversing the plus sign and the each in turn, the process of separating the I and Q signals, the A 3. The data compression apparatus for pulse compression radar according to claim 1, wherein the repetition is performed based on a magnification of the center frequency that determines a / D conversion speed .   4. The data compression apparatus for pulse compression radar according to claim 3, wherein the reference function used in the correlation processing unit is composed of a component having a frequency characteristic opposite to a signal component. In I Q separation process, the sample data after A / D conversion, negative, positive sign and the plus, while reversing the minus sign and the each in turn, the process of separating the I and Q signals, the A 3. The data compression apparatus for pulse compression radar according to claim 1, wherein the repetition is performed based on a magnification of the center frequency that determines a / D conversion speed .   6. The data compression apparatus for pulse compression radar according to claim 5, wherein the reference function used in the correlation processing unit is composed of a component having the same frequency characteristic as a signal component. In a pulse compression radar apparatus having a transmission unit that transmits a frequency-modulated pulse signal toward a target, and a reception unit that performs reception processing by applying pulse compression processing to the radar reception signal,
The receiving unit, pulse compression radar apparatus comprising: a pulse compression radar data reproducing apparatus according to any one of claims 1 to 6. The first receiving unit having the data processing unit according to any one of claims 1 to 6, and the second receiving unit having the pulse compression processing unit according to any one of claims 1 to 6. And comprising
8. The pulse compression radar apparatus according to claim 7 , wherein the first reception unit transmits the thinned data as sampling data for pulse compression processing to the second reception unit . 9. The pulse compression radar apparatus according to claim 8, wherein the thinned data is received from a first reception unit of another pulse compression radar apparatus. Down-converts the received radar signal indicating the pulse-compressed radar transmission signal, converts the frequency to the center frequency, and filters the received frequency-converted radar reception signal to obtain a bandwidth signal centered on the center frequency. And the frequency of the filtered signal is A / D converted at an A / D conversion speed four times the center frequency, and then separated into an I signal and a Q signal. In the data recovery method for pulse compression radar,
After I Q separation, n <fs / B (where thinning rate n, the bandwidth B, and the A / D conversion speed and fs) so as to satisfy the, to the IQ separation processing signals A process of thinning ,
And facilities to process the zero-filled process which means that there is no data to thinned data portion,
For the result of FFT (Fast Fourier Transform) processing and zero-padded data conversion to frequency axis data, pulse compression of the signal component from which the virtual image signal is removed by correlation processing using a reference function A process of performing ;
A data reproduction method for pulse compression radar, comprising: In the step of performing the zero padding process, a zero padding process that means that there is no data for the empty data portion by alternately shifting the output order of the I signal and Q signal subjected to the thinning process in time. The data reproduction method for pulse compression radar according to claim 10, wherein the method is applied. In the step of performing I Q separation process, the sample data after A / D conversion, plus, minus and minus, while reversing the plus sign and the each in turn, the process of separating the I and Q signals The data reproduction method for pulse compression radar according to claim 10, wherein the method is repeated based on a magnification of the center frequency that defines the A / D conversion speed .   13. The data reproduction method for pulse compression radar according to claim 12, wherein the reference function used in the correlation processing is composed of a component having a frequency characteristic opposite to a signal component. In the step of performing the IQ separation process , the sample data after A / D conversion is separated into the I signal and the Q signal while inverting the minus and plus signs and the plus and minus signs respectively. The data reproduction method for pulse compression radar according to claim 10, wherein the method is repeated based on a magnification of the center frequency that defines the A / D conversion speed .   15. The data reproduction method for pulse compression radar according to claim 14, wherein the reference function used in the correlation processing unit includes a component having the same frequency characteristic as a signal component.   Down-converts the received radar signal indicating the pulse-compressed radar transmission signal, converts the frequency to the center frequency, and filters the received frequency-converted radar reception signal to obtain a bandwidth signal centered on the center frequency. And the frequency of the filtered signal is A / D converted at an A / D conversion speed four times the center frequency, and then separated into an I signal and a Q signal. In the program for executing the data recovery method for pulse compression radar,
  On the computer,
  After IQ separation processing, the signals subjected to the IQ separation processing are thinned so as to satisfy n <fs / B (where the thinning rate is n, the bandwidth is B, and the A / D conversion speed is fs). Processing to perform processing,
  A process of performing zero padding processing that means no data for the thinned data portion;
  For the result of FFT (Fast Fourier Transform) processing and zero-padded data conversion to frequency axis data, pulse compression of the signal component from which the virtual image signal is removed by correlation processing using a reference function What to do,
A program characterized by having executed.

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