WO2022085044A1 - Radar signal processing device and radar signal processing method - Google Patents

Radar signal processing device and radar signal processing method Download PDF

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Publication number
WO2022085044A1
WO2022085044A1 PCT/JP2020/039224 JP2020039224W WO2022085044A1 WO 2022085044 A1 WO2022085044 A1 WO 2022085044A1 JP 2020039224 W JP2020039224 W JP 2020039224W WO 2022085044 A1 WO2022085044 A1 WO 2022085044A1
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unit
channel signals
imbalance correction
channel
band
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PCT/JP2020/039224
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French (fr)
Japanese (ja)
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智也 山岡
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三菱電機株式会社
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Priority to JP2022556832A priority Critical patent/JP7214061B2/en
Priority to PCT/JP2020/039224 priority patent/WO2022085044A1/en
Publication of WO2022085044A1 publication Critical patent/WO2022085044A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
    • G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques

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  • This disclosure relates to a radar signal processing device.
  • the multi-channel synthetic aperture radar (hereinafter referred to as multi-channel SAR) is provided with a plurality of receiving antennas, so that a plurality of signals (hereinafter referred to as a plurality of channel signals) are received via a plurality of channels.
  • the multi-channel synthetic aperture radar generates a SAR image by performing a restoration process based on a plurality of received channel signals.
  • the multi-channel synthetic aperture radar corrects the amount of deviation between channel signals (hereinafter referred to as imbalance) caused by the difference in channels (for example, Non-Patent Document 1).
  • the azimuth ambiguity is multiplexed, and the above-mentioned is performed with sufficient accuracy. There is a problem that it becomes difficult to correct the imbalance between the channel signals of.
  • the present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to provide a technique for improving the accuracy of imbalance correction between channel signals.
  • the hit region band limiting unit and the hit region band limiting unit that limit the bandwidth in the hit region hit a plurality of channel signals obtained by observation by the multi-channel SAR, respectively. It includes an imbalance correction unit that performs imbalance correction between channel signals based on a plurality of channel signals for which band limitation has been performed in a region.
  • the accuracy of imbalance correction between channel signals can be improved.
  • FIG. 4A is a block diagram showing a hardware configuration that realizes the functions of the radar signal processing device according to the first embodiment.
  • FIG. 4B is a block diagram showing a hardware configuration for executing software that realizes the functions of the radar signal processing device according to the first embodiment.
  • FIG. 1 is a block diagram showing a configuration of a radar signal processing device 100 according to the first embodiment.
  • the radar signal processing device 100 includes a power imbalance correction unit 1, a fast Fourier transform unit 2, a Doppler frequency domain band limiting unit 3, an inverse fast Fourier transform unit 4, a hit region band limiting unit 5, and an in. It includes a balance correction unit 6, a sub-aperture division unit 9, a restoration algorithm unit 10, an image reproduction unit 11, and a sub-aperture coupling unit 12.
  • the power imbalance correction unit 1 corrects the power imbalance for a plurality of channel signals (raw data) obtained by observation by the multi-channel SAR.
  • the power imbalance correction unit 1 outputs a plurality of channel signals that have undergone power imbalance correction to the fast Fourier transform unit 2.
  • the "plurality of channel signals” means signals obtained from the corresponding channels among the plurality of channels in the multi-channel SAR, respectively.
  • power imbalance correction means to correct the amount of power deviation between channel signals caused by a channel difference.
  • the observation by the multi-channel SAR is a sliding spot observation.
  • the configuration in which the observation by the multi-channel SAR is the sliding spot observation will be described, but the observation by the multi-channel SAR may be, for example, a full spotlight observation or the like.
  • the fast Fourier transform unit 2 performs Doppler frequency conversion for each of a plurality of channel signals obtained by observation by the multi-channel SAR.
  • the fast Fourier transform unit 2 converts a plurality of channel signals obtained by observation by the multi-channel SAR into signals in the Doppler frequency domain by performing a fast Fourier transform. do.
  • the fast Fourier transform unit 2 performs Doppler frequency conversion for each of the plurality of channel signals for which the power imbalance correction unit 1 has performed the power imbalance correction.
  • the fast Fourier transform unit 2 outputs a plurality of channel signals that have undergone Doppler frequency conversion to the Doppler frequency domain band limiting unit 3.
  • the Doppler frequency domain band limiting unit 3 limits the band in the Doppler frequency domain for each of the plurality of channel signals for which the fast Fourier transform unit 2 has undergone the Doppler frequency conversion. More specifically, in the first embodiment, the Doppler frequency domain band limiting unit 3 extracts a channel signal in a band centered on the Doppler center frequency by band limiting in the Doppler frequency domain. The Doppler frequency domain band limiting unit 3 outputs a plurality of channel signals band-limited in the Doppler frequency domain to the inverse fast Fourier transform unit 4.
  • the inverse fast Fourier transform unit 4 (inverse Doppler frequency converter) performs inverse Doppler frequency conversion for each of a plurality of channel signals for which the Doppler frequency domain band limiting unit 3 has band-limited in the Doppler frequency domain.
  • the inverse fast Fourier transform unit 4 performs an inverse fast Fourier transform on each of a plurality of channel signals for which the Doppler frequency domain band limiting unit 3 has band-limited in the Doppler frequency domain, thereby performing a fast Fourier transform.
  • the transforming unit 2 converts the signal into the signal in the original time domain before performing the fast Fourier transform.
  • the inverse fast Fourier transform unit 4 outputs a plurality of channel signals subjected to the inverse Doppler frequency conversion to the hit region band limiting unit 5.
  • the hit area band limiting unit 5 limits the band in the hit area for each of the plurality of channel signals obtained by the observation by the multi-channel SAR. More specifically, in the first embodiment, the hit region band limiting unit 5 limits the bandwidth in the hit region for each of the plurality of channel signals subjected to the inverse Doppler frequency conversion by the inverse fast Fourier transform unit 4. .. More specifically, in the first embodiment, the hit region band limiting unit 5 extracts a channel signal in a band centered on the hit center by band limiting in the hit region. The hit area band limiting unit 5 outputs a plurality of channel signals for which the band is limited in the hit area to the imbalance correction unit 6.
  • the imbalance correction unit 6 performs imbalance correction between channel signals based on a plurality of channel signals for which the hit region band limiting unit 5 has band-limited in the hit region. More specifically, in the first embodiment, the imbalance correction unit 6 corrects the phase imbalance as the imbalance correction between the channel signals. The imbalance correction unit 6 outputs a plurality of channel signals for which imbalance correction has been performed to the sub-aperture division unit 9.
  • phase imbalance means the amount of phase shift between channel signals caused by the difference in channels.
  • the imbalance correction unit 6 corrects the phase imbalance as the imbalance correction will be described, but the imbalance correction unit 6 corrects the range sample deviation as the imbalance correction between the channel signals. May be done.
  • the imbalance correction unit 6 includes a Doppler center frequency estimation unit 7 and a phase imbalance correction unit 8.
  • the Doppler center frequency estimation unit 7 estimates the Doppler center frequencies of a plurality of channel signals for which the hit region band limiting unit 5 has band-limited in the hit region.
  • the Doppler center frequency estimation unit 7 outputs the estimated Doppler center frequency to the phase imbalance correction unit 8.
  • the phase imbalance correction unit 8 is based on the Doppler center frequency estimated by the Doppler center frequency estimation unit 7, and is based on a plurality of channel signals for which the hit region band limiting unit 5 has band-limited in the hit region. The phase imbalance of is corrected.
  • the phase imbalance correction unit 8 outputs a plurality of channel signals for which the phase imbalance has been corrected to the sub-aperture division unit 9.
  • the sub-aperture division unit 9 performs sub-aperture division for a plurality of channel signals for which the imbalance correction unit 6 has performed imbalance correction. More specifically, in the first embodiment, the sub-aperture division unit 9 divides the sub-aperture into a plurality of channel signals for which the phase imbalance correction unit 8 of the imbalance correction unit 6 has corrected the phase imbalance. I do. The sub-aperture division unit 9 outputs a plurality of channel signals obtained by sub-aperture division to the restoration algorithm unit 10.
  • the restoration algorithm unit 10 performs a restoration algorithm on a plurality of channel signals for which the sub-aperture division unit 9 has performed sub-aperture division.
  • the restoration algorithm unit 10 outputs a plurality of channel signals subjected to the restoration algorithm to the image reproduction unit 11.
  • the image reproduction unit 11 reproduces an image on a plurality of channel signals for which the restoration algorithm unit 10 has performed the restoration algorithm.
  • the image reproduction unit 11 outputs a plurality of channel signals for which image reproduction has been performed to the sub-aperture coupling unit 12.
  • the sub-aperture coupling unit 12 generates a SAR image by performing sub-aperture coupling on a plurality of channel signals for which the image reproduction unit 11 has reproduced an image. For example, the SAR image generated by the sub-aperture coupling portion 12 is displayed by a display (not shown).
  • FIG. 2 is a flowchart showing a radar signal processing method by the radar signal processing device 100 according to the first embodiment. Before each step described below, it is assumed that the radar signal processing device 100 has acquired a plurality of channel signals obtained by observation by the multi-channel SAR.
  • the power imbalance correction unit 1 performs power imbalance correction on a plurality of channel signals obtained by observation by the multi-channel SAR (step ST1).
  • the power imbalance correction unit 1 outputs a plurality of channel signals that have undergone power imbalance correction to the fast Fourier transform unit 2.
  • the fast Fourier transform unit 2 performs Doppler frequency conversion for each of the plurality of channel signals for which the power imbalance correction unit 1 has performed the power imbalance correction (step ST2).
  • the fast Fourier transform unit 2 outputs a plurality of channel signals that have undergone Doppler frequency conversion to the Doppler frequency domain band limiting unit 3.
  • the Doppler frequency domain band limiting unit 3 limits the band in the Doppler frequency domain for each of the plurality of channel signals subjected to the Doppler frequency conversion by the fast Fourier transform unit 2 (step ST3).
  • the Doppler frequency domain band limiting unit 3 outputs a plurality of channel signals band-limited in the Doppler frequency domain to the inverse fast Fourier transform unit 4.
  • the inverse fast Fourier transform unit 4 performs inverse Doppler frequency conversion for each of the plurality of channel signals for which the Doppler frequency domain band limiting unit 3 has band-limited in the Doppler frequency domain (step ST4).
  • the inverse fast Fourier transform unit 4 outputs a plurality of channel signals subjected to the inverse Doppler frequency conversion to the hit region band limiting unit 5.
  • the hit region band limiting unit 5 limits the bandwidth in the hit region for each of the plurality of channel signals for which the inverse fast Fourier transform unit 4 has undergone the inverse Doppler frequency conversion (step ST5).
  • the hit area band limiting unit 5 outputs a plurality of channel signals for which the band is limited in the hit area to the imbalance correction unit 6.
  • the Doppler center frequency estimation unit 7 of the imbalance correction unit 6 estimates the Doppler center frequency of a plurality of channel signals for which the hit region band limiting unit 5 has band-limited in the hit region (step ST6).
  • the Doppler center frequency estimation unit 7 outputs the estimated Doppler center frequency to the phase imbalance correction unit 8.
  • the phase imbalance correction unit 8 of the imbalance correction unit 6 corrects the phase imbalance between the channel signals based on the Doppler center frequency estimated by the Doppler center frequency estimation unit 7 (step ST7).
  • the phase imbalance correction unit 8 outputs a plurality of channel signals for which the phase imbalance has been corrected to the sub-aperture division unit 9.
  • the sub-aperture division unit 9 performs sub-aperture division for a plurality of channel signals for which the imbalance correction unit 6 has corrected the phase imbalance (step ST8).
  • the sub-aperture division unit 9 outputs a plurality of channel signals obtained by sub-aperture division to the restoration algorithm unit 10.
  • the restoration algorithm unit 10 performs a restoration algorithm on a plurality of channel signals for which the sub-aperture division unit 9 has undergone sub-aperture division (step ST9).
  • the restoration algorithm unit 10 outputs a plurality of channel signals subjected to the restoration algorithm to the image reproduction unit 11.
  • the image reproduction unit 11 reproduces an image on a plurality of channel signals for which the restoration algorithm unit 10 has performed the restoration algorithm (step ST10).
  • the image reproduction unit 11 outputs a plurality of channel signals for which image reproduction has been performed to the sub-aperture coupling unit 12.
  • the sub-aperture coupling unit 12 generates a SAR image by performing sub-aperture coupling on a plurality of channel signals for which the image reproduction unit 11 has reproduced an image (step ST11). For example, the SAR image generated by the sub-aperture coupling unit 12 in step ST11 is displayed by a display (not shown).
  • FIG. 3 is a diagram showing the progress of a channel signal processed by the radar signal processing method by the radar signal processing device 100 according to the first embodiment.
  • the plurality of channel signals obtained by the observation by the multi-channel SAR are the signals obtained by the two-channel sliding spotlight observation.
  • the first channel signal (channel 0 signal) before being processed by the radar signal processing device 100 is s 0 ( ⁇ , ⁇ ), and the second channel signal (channel 1 signal) is s 1 ( ⁇ , ⁇ ). ).
  • ⁇ is the range time and ⁇ is a hit.
  • the first channel signal will be used as a reference channel.
  • the power imbalance correction unit 1 has the following with respect to the first channel signal s 0 ( ⁇ , ⁇ ) and the second channel signal s 1 ( ⁇ , ⁇ ). Power imbalance correction is performed according to the method described in (For example, Non-Patent Document J. H. Kim, M. Younis, P. P. Iraola, M. Gebele, and G. Krieger, “First spaceborne demonstration of digital beamforming for azimuth ambiguity suppression”, IEEE. See Trans. Geosci. Remote Sens., Vol.51, no.1, pp.579-590, Jan., 2013).
  • the power imbalance correction unit 1 uses the first channel signal s 0 ( ⁇ , ⁇ ) and the second channel signal s 1 ( ⁇ , ⁇ ) to correct the power imbalance in the range frequency region. On the other hand, range frequency conversion is performed. As a result, the power imbalance correction unit 1 obtains S 0 ( fr , ⁇ ) and S 1 ( fr , ⁇ ) with the range frequency as fr .
  • the power imbalance correction unit 1 sets the noise power generated by the first channel signal as ⁇ 0 2 , and the noise power generated by the second channel signal as ⁇ 1 2 , according to the following equation (1).
  • the correction coefficient ⁇ ( fr ) of the power (amplitude) imbalance is calculated.
  • 2 ) indicates the average of
  • 2 ) indicates the average of
  • the power imbalance correction unit 1 corrects the amplitude of S 1 ( fr , ⁇ ) according to the following equation (2) based on the calculated correction coefficient ⁇ (fr).
  • the power imbalance correction unit 1 corrects the power imbalance by performing range time conversion on S 1 '( fr , ⁇ ) obtained by the equation (2).
  • the power imbalance correction unit 1 may use a method other than the method of the specific example as a method of correcting the power imbalance.
  • FIG. 3A shows a graph of the first channel signal s 0 ( ⁇ , ⁇ ) after the processing of step ST1.
  • the vertical axis in A indicates a hit
  • the horizontal axis indicates a range.
  • the raw data of the seven point images are multiplexed in the hit-range space.
  • the fast Fourier transform unit 2 has a Doppler frequency with respect to the first channel signal s 0 ( ⁇ , ⁇ ) and the second channel signal s 1 '( ⁇ , ⁇ ), respectively.
  • FIG. 3B shows a graph of the first channel signal after the processing of step ST2.
  • the vertical axis in B indicates the Doppler frequency
  • the horizontal axis indicates the range.
  • the first channel signal s 0 ( ⁇ , ⁇ ) is multiplexed with azimuth ambiguity.
  • the azimuth ambiguity is similarly multiplexed for the second channel signal s 1 '( ⁇ , ⁇ ).
  • FIG. 3C shows a graph of the first channel signal after the processing of step ST3.
  • the vertical axis in C in FIG. 3 indicates the Doppler frequency, and the horizontal axis indicates the range.
  • a signal near the Doppler center frequency is extracted by the process of step ST3.
  • a signal near the Doppler center frequency is similarly extracted by the process of step ST3.
  • step ST4 the inverse fast Fourier transform unit 4 performs inverse Doppler frequency conversion on the first channel signal and the second channel signal obtained by the processing of step ST3.
  • FIG. 3D shows a graph of the first channel signal after the processing of step ST4.
  • the vertical axis in D in FIG. 3 indicates a hit, and the horizontal axis indicates a range.
  • D in FIG. 3 in the first channel signal s 0 ( ⁇ , ⁇ ) after the processing of step ST4, the signals are discretely dispersed.
  • the signals of the second channel signal s 1 '( ⁇ , ⁇ ) after the processing of step ST4 are also discretely dispersed.
  • the hit region band limiting unit 5 has a hit region for each hit-range component of the first channel signal and the second channel signal obtained by the processing of step ST4.
  • FIG. 3E shows a graph of the first channel signal after the processing of step ST5.
  • the vertical axis in E in FIG. 3 indicates a hit, and the horizontal axis indicates a range.
  • E in FIG. 3 by suppressing the azimuth ambiguity, a signal from which the azimuth ambiguity is separated is obtained.
  • a signal from which the azimuth ambiguity is separated can be obtained similarly for the second channel signal s 1 '( ⁇ , ⁇ ).
  • the first channel signal obtained by the process of step ST5 is s 0 ( ⁇ , ⁇ )
  • the second channel signal is s 1 '( ⁇ , ⁇ ).
  • the imbalance correction unit 6 performs the first channel signal s 0 ( ⁇ , ⁇ ) and the second channel signal s 1 '( ⁇ ) obtained by the processing of step ST5. , ⁇ ), and corrects the phase imbalance between the channel signals according to the method described below (eg, H. Fan, Z. Zhang, and R. Wang, “phase mismatch calibration for multichannel sliding spotlight SAR). imaging with extended azimuth cross correlation ”, see IGARSS 2019).
  • step ST6 the Doppler center frequency estimation unit 7 of the imbalance correction unit 6 is based on the first channel signal s 0 ( ⁇ , ⁇ ) and the second channel signal s 1 '( ⁇ , ⁇ ). Then, two interference data C 1,0 ( ⁇ ) and C 0,1 ( ⁇ ) are calculated according to the following equations (3) and (4).
  • the PRF is the pulse repetition frequency and corresponds to one sample shift in the azimuth direction in the channel signal.
  • E ⁇ () indicates the average of the equations in parentheses in the hit direction, as described above.
  • the Doppler center frequency estimation unit 7 calculates the product C 1,0 ( ⁇ ) C 0,1 ( ⁇ ) of both the interference data C 1,0 ( ⁇ ) and C 0,1 ( ⁇ ). Therefore, the phase imbalance contained in s 1 '( ⁇ , ⁇ ) is offset. Assuming that the Doppler center frequency is f dc ( ⁇ ), the relationship of the following equation (5) is obtained.
  • the Doppler center frequency estimation unit 7 calculates the Doppler center frequency f dc ( ⁇ ) based on the calculated C 1,0 ( ⁇ ) C 0,1 ( ⁇ ) according to the following equation (6).
  • the phase imbalance correction unit 8 of the imbalance correction unit 6 has the following equation (7) based on the Doppler center frequency f dc ( ⁇ ) calculated by the Doppler center frequency estimation unit 7.
  • the phase imbalance ⁇ ( ⁇ ) is calculated according to the above.
  • vs represents the platform speed
  • d represents the distance between the reception phase centers of the two channels.
  • the phase imbalance correction unit 8 generates a weight for the obtained phase imbalance ⁇ ( ⁇ ) and performs a weighted averaging process so as to take an expected value in the hit direction. This process reduces the error in the estimated value. More specifically, first, the phase imbalance correction unit 8 calculates the average of
  • the phase imbalance correction unit 8 takes a weighted average according to the following equation (9) and calculates the phase imbalance ⁇ .
  • E ⁇ ⁇ indicates the average of the equations in parentheses in the range time direction.
  • the phase imbalance correction unit 8 corrects the phase imbalance between the channel signals according to the following equation (10) based on the calculated phase imbalance ⁇ . More specifically, in the specific example, the phase imbalance correction unit 8 has the second channel signal s after the power imbalance correction described above according to the following equation (10) based on the calculated phase imbalance ⁇ . Correct the phase imbalance for 1 '( ⁇ , ⁇ ).
  • the imbalance correction unit 6 may use a method other than the method of the specific example as a method of correcting the phase imbalance.
  • the sub-aperture dividing unit 9 has the second channel signal s 1 '' ( ⁇ , ⁇ ) and the first channel signal s 0 ( ⁇ , ⁇ ) after the processing of step ST7.
  • the method of sub-aperture division for example, the non-patent document J. Mittermayer, R. Lord, and E. B ⁇ oner, “Sliding spotlight SAR processing for TerraSAR-X using a new” fomulation of the extended chirp scaling algorithm, ”IGARSS2003, vol.3, p.1462-1464, 2003.).
  • the restoration algorithm unit 10 performs a restoration algorithm on the first channel signal and the second channel signal to which the sub-aperture division unit 9 has performed the sub-aperture division (reconstruction algorithm).
  • a restoration algorithm for the method, see, for example, Non-Patent Document 1 described above).
  • the image reproduction unit 11 reproduces an image with respect to the first channel signal and the second channel signal to which the restoration algorithm unit 10 has performed the restoration algorithm.
  • the image reproduction method include extended chirp scaling (for example, the above-mentioned non-patent documents J. Mittermayer, R. Lord, and E. B ⁇ oner, “Sliding spotlight SAR processing for TerraSAR-X using a”. See new fomulation of the extended chirp scaling algorithm, ”IGARSS2003, vol.3, p.1462-1464, 2003.).
  • the sub-aperture coupling unit 12 obtains a SAR image by performing sub-aperture coupling to the first channel signal and the second channel signal for which the image reproduction unit 11 has reproduced the image. Generate.
  • the imbalance correction unit 6 only corrects the phase imbalance in the subsequent stage of the band limitation by the bandpass filter twice, but the imbalance correction unit 6 corrects the range sample deviation and the like. Other imbalance corrections may be made.
  • the band path filters of the Doppler frequency domain band limiting unit 3 and the hit region band limiting unit 5 performed the band limitation twice, the Doppler frequency domain band limiting unit 3 did not limit the band of the Doppler frequency region.
  • the hit area band limiting unit 5 may limit the band only in the hit area.
  • Each function of the frequency estimation unit 7, the phase imbalance correction unit 8, the sub-aperture division unit 9, the restoration algorithm unit 10, the image reproduction unit 11, and the sub-aperture coupling unit 12 is realized by a processing circuit. That is, the radar signal processing device 100 includes a processing circuit for executing the processing of each step shown in FIG. This processing circuit may be dedicated hardware, or may be a CPU (Central Processing Unit) that executes a program stored in the memory.
  • CPU Central Processing Unit
  • FIG. 4A is a block diagram showing a hardware configuration that realizes the functions of the radar signal processing device 100.
  • FIG. 4B is a block diagram showing a hardware configuration for executing software that realizes the functions of the radar signal processing device 100.
  • the processing circuit 20 may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, or an ASIC (Application Specific Integrated Circuitd). Circuit), FPGA (Field-Programmable Gate Array) or a combination thereof is applicable.
  • ASIC Application Specific Integrated Circuitd
  • FPGA Field-Programmable Gate Array
  • Doppler center of power imbalance correction unit 1 Doppler center of power imbalance correction unit 1, fast Fourier transform unit 2, Doppler frequency domain band limiting unit 3, inverse fast Fourier transform unit 4, hit region band limiting unit 5, and imbalance correction unit 6 in the radar signal processing device 100.
  • the functions of the frequency estimation unit 7, the phase imbalance correction unit 8, the sub-aperture division unit 9, the restoration algorithm unit 10, the image reproduction unit 11, and the sub-aperture coupling unit 12 may be realized by separate processing circuits, or these may be realized. The functions may be collectively realized by one processing circuit.
  • the power imbalance correction unit 1 When the processing circuit is the processor 21 shown in FIG. 4B, the power imbalance correction unit 1, the fast Fourier transform unit 2, the Doppler frequency domain band limiting unit 3, the inverse fast Fourier transform unit 4, and the hit in the radar signal processing device 100.
  • the software or firmware is described as a program and stored in the memory 22.
  • the processor 21 By reading and executing the program stored in the memory 22, the processor 21 reads and executes the power imbalance correction unit 1, the fast Fourier transform unit 2, the Doppler frequency domain band limiting unit 3, and the inverse high-speed Fourier in the radar signal processing device 100. Conversion unit 4, hit region band limiting unit 5, Doppler center frequency estimation unit 7 and phase imbalance correction unit 8 of imbalance correction unit 6, sub-aperture division unit 9, restoration algorithm unit 10, image reproduction unit 11, and sub-aperture coupling. Each function of the part 12 is realized. That is, the radar signal processing device 100 includes a memory 22 for storing a program in which the processing of each step shown in FIG. 2 is executed as a result when each of these functions is executed by the processor 21.
  • These programs include a power imbalance correction unit 1, a high-speed Fourier transform unit 2, a Doppler frequency domain band limiting unit 3, an inverse fast Fourier transform unit 4, a hit region band limiting unit 5, and an imbalance correction in the radar signal processing device 100.
  • the computer is made to execute each procedure or method of the Doppler center frequency estimation unit 7 of the unit 6, the phase imbalance correction unit 8, the sub-aperture division unit 9, the restoration algorithm unit 10, the image reproduction unit 11, and the sub-aperture coupling unit 12.
  • the memory 22 uses the computer as a power imbalance correction unit 1, a fast Fourier transform unit 2, a Doppler frequency domain band limiting unit 3, an inverse fast Fourier transform unit 4, a hit region band limiting unit 5, and an algorithm in the radar signal processing device 100.
  • a program for functioning as the Doppler center frequency estimation unit 7 of the balance correction unit 6, the phase imbalance correction unit 8, the sub-aperture division unit 9, the restoration algorithm unit 10, the image reproduction unit 11, and the sub-aperture coupling unit 12 is stored. It may be a computer-readable storage medium.
  • the processor 21 corresponds to, for example, a CPU (Central Processing Unit), a processing device, a computing device, a processor, a microprocessor, a microcomputer, a DSP (Digital Signal Processor), or the like.
  • the memory 22 may include, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), an EPROM (Electrically-volatile) semiconductor, or an EPROM (Electrically-EPROM).
  • a RAM Random Access Memory
  • ROM Read Only Memory
  • flash memory an EPROM (Erasable Programmable Read Only Memory)
  • EPROM Electrically-volatile semiconductor
  • EPROM Electrically-EPROM
  • Doppler center of power imbalance correction unit 1 Doppler center of power imbalance correction unit 1, fast Fourier transform unit 2, Doppler frequency domain band limiting unit 3, inverse fast Fourier transform unit 4, hit region band limiting unit 5, and imbalance correction unit 6 in the radar signal processing device 100.
  • Some of the functions of the frequency estimation unit 7, the phase imbalance correction unit 8, the sub-aperture division unit 9, the restoration algorithm unit 10, the image reproduction unit 11, and the sub-aperture coupling unit 12 are realized by dedicated hardware, and some of them are realized. May be realized by software or firmware.
  • each function of the power imbalance correction unit 1, the fast Fourier transform unit 2, the Doppler frequency domain band limiting unit 3, the inverse fast Fourier transform unit 4, and the hit region band limiting unit 5 is a processing circuit as dedicated hardware. Realize the function.
  • the processor 21 is stored in the memory 22. The function may be realized by reading and executing the stored program.
  • the processing circuit can realize each of the above functions by hardware, software, firmware or a combination thereof.
  • the radar signal processing device 100 has the hit area band limiting unit 5 that limits the band in the hit area for each of the plurality of channel signals obtained by the observation by the multi-channel SAR. And an imbalance correction unit 6 that performs imbalance correction between channel signals based on a plurality of channel signals for which the hit region band limiting unit 5 has band-limited in the hit region.
  • a signal in which the azimuth ambiguity is separated can be obtained due to the band limitation in the hit region.
  • the accuracy of imbalance correction between channel signals can be improved.
  • the hit region band limiting unit 5 in the radar signal processing device 100 extracts a channel signal in a band centered on the hit center by band limiting in the hit region. According to the above configuration, a signal in which the azimuth ambiguity is separated can be obtained by band limitation for extracting the channel signal in the band centered on the hit center. By performing imbalance correction on the signal obtained thereby, the accuracy of imbalance correction between channel signals can be improved.
  • the radar signal processing device 100 has a high-speed Fourier conversion unit 2 that performs Doppler frequency conversion on a plurality of channel signals, and a plurality of channels that the high-speed Fourier conversion unit 2 performs Doppler frequency conversion.
  • the Doppler frequency domain band limiting unit 3 that limits the band in the Doppler frequency domain and the plurality of channel signals that the Doppler frequency domain band limiting section 3 band limits in the Doppler frequency domain, respectively.
  • Inverse high-speed Fourier conversion unit 4 that performs inverse Doppler frequency conversion, and the hit region band limiting unit 5 for each of a plurality of channel signals that the inverse high-speed Fourier conversion unit 4 has performed inverse Doppler frequency conversion.
  • Band limitation in the hit area For each of the signals, the Doppler frequency domain band limiting unit 3 that limits the band in the Doppler frequency domain and the plurality of channel signals that the Doppler frequency domain band limiting section 3 band limits in the Doppler frequency domain.
  • a signal in which the azimuth ambiguity is separated can be obtained due to the band limitation in the hit region and the band limitation in the Doppler frequency region.
  • the Doppler frequency domain band limiting unit 3 in the radar signal processing device 100 extracts a channel signal in a band centered on the Doppler center frequency by band limiting in the Doppler frequency domain.
  • a signal in which the azimuth ambiguity is separated can be obtained by band limitation for extracting the channel signal in the band centered on the Doppler center frequency.
  • the imbalance correction unit 6 in the radar signal processing device 100 corrects the phase imbalance as the imbalance correction. According to the above configuration, the accuracy of the phase imbalance correction between the channel signals can be improved by performing the phase imbalance correction on the signal whose azimuth ambiguity is separated by the band limitation.
  • the imbalance correction unit 6 in the radar signal processing device 100 may correct the range sample deviation as the imbalance correction. According to the above configuration, it is possible to improve the correction accuracy of the range sample deviation between the channel signals by correcting the range sample deviation for the signal whose azimuth ambiguity is separated by the band limitation.
  • the observation by the multi-channel SAR in the radar signal processing apparatus 100 according to the first embodiment is a sliding spot observation or a full spotlight observation. According to the above configuration, when the azimuth ambiguity is multiplexed by sliding spot observation or full spotlight observation, the accuracy of imbalance correction between channel signals can be improved.
  • a hit area band limiting step and a hit area band limiting step for band limiting in the hit region are performed for a plurality of channel signals obtained by observation by the multi-channel SAR, respectively.
  • the radar processing device can be used in the multi-channel SAR technique because it can improve the accuracy of imbalance correction between channel signals.
  • 1 power imbalance correction unit 1 power imbalance correction unit, 2 high-speed Fourier transform unit, 3 Doppler frequency domain band limiting unit, 4 inverse fast Fourier transform unit, 5 hit region band limiting unit, 6 imbalance correction unit, 7 Doppler center frequency estimation unit, 8 phase Imbalance correction unit, 9 sub-aperture division unit, 10 restoration algorithm unit, 11 image reproduction unit, 12 sub-aperture coupling unit, 20 processing circuit, 21 processor, 22 memory, 100 radar signal processing device.

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Abstract

A radar signal processing device (100) comprises: a hit-region band limiting unit (5) for limiting a band in a hit region with respect to each of a plurality of channel signals obtained by observation using a multichannel SAR; and an imbalance correction unit (6) for correcting imbalance between channel signals on the basis of the plurality of channel signals that have been subjected to the band limitation in the hit region by the hit-region band limiting unit (5).

Description

レーダ信号処理装置、及びレーダ信号処理方法Radar signal processing device and radar signal processing method
　本開示は、レーダ信号処理装置に関する。 This disclosure relates to a radar signal processing device.
　マルチチャネル合成開口レーダ（以下、マルチチャネルＳＡＲと称する）は、複数の受信アンテナを備えていることにより、複数のチャネルを介して複数の信号（以下、複数のチャネル信号と称する）を受信する。マルチチャネル合成開口レーダは、受信した複数のチャネル信号に基づいて、復元処理を行うことによりＳＡＲ画像を生成する。その際、マルチチャネル合成開口レーダは、チャネルの相違に伴って生じるチャネル信号間のずれ量（以下、インバランスと称する）を補正する（例えば、非特許文献１）。 The multi-channel synthetic aperture radar (hereinafter referred to as multi-channel SAR) is provided with a plurality of receiving antennas, so that a plurality of signals (hereinafter referred to as a plurality of channel signals) are received via a plurality of channels. The multi-channel synthetic aperture radar generates a SAR image by performing a restoration process based on a plurality of received channel signals. At that time, the multi-channel synthetic aperture radar corrects the amount of deviation between channel signals (hereinafter referred to as imbalance) caused by the difference in channels (for example, Non-Patent Document 1).
　上述のマルチチャネル合成開口レーダにおいて、例えば、さらなるアジマス高分解能化を実現するためにスライディングスポットライト観測又はフルスポットライト観測等を行う場合、アジマスアンビギュイティが多重化してしまい、十分な精度で上述のチャネル信号間のインバランスを補正することが困難になるという問題がある。 In the above-mentioned multi-channel synthetic aperture radar, for example, when performing sliding spotlight observation or full spotlight observation in order to realize further high resolution of azimuth, the azimuth ambiguity is multiplexed, and the above-mentioned is performed with sufficient accuracy. There is a problem that it becomes difficult to correct the imbalance between the channel signals of.
　本開示は、上記のような問題点を解決するためになされたものであり、チャネル信号間のインバランス補正の精度を向上させる技術を提供することを目的とする。 The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to provide a technique for improving the accuracy of imbalance correction between channel signals.
　本開示に係るレーダ信号処理装置は、マルチチャネルＳＡＲによる観測によって得られた複数のチャネル信号に対して、それぞれ、ヒット領域における帯域制限を行うヒット領域帯域制限部と、ヒット領域帯域制限部がヒット領域における帯域制限を行った複数のチャネル信号に基づいて、チャネル信号間のインバランス補正を行うインバランス補正部と、を備えている。 In the radar signal processing apparatus according to the present disclosure, the hit region band limiting unit and the hit region band limiting unit that limit the bandwidth in the hit region hit a plurality of channel signals obtained by observation by the multi-channel SAR, respectively. It includes an imbalance correction unit that performs imbalance correction between channel signals based on a plurality of channel signals for which band limitation has been performed in a region.
　本開示によれば、チャネル信号間のインバランス補正の精度を向上させることができる。 According to the present disclosure, the accuracy of imbalance correction between channel signals can be improved.
実施の形態１に係るレーダ信号処理装置の構成を示すブロック図である。It is a block diagram which shows the structure of the radar signal processing apparatus which concerns on Embodiment 1. FIG. 実施の形態１に係るレーダ信号処理装置によるレーダ信号処理方法を示すフローチャートである。It is a flowchart which shows the radar signal processing method by the radar signal processing apparatus which concerns on Embodiment 1. 実施の形態１に係るレーダ信号処理装置によるレーダ信号処理方法によって処理されたチャネル信号の途中経過を示す図である。It is a figure which shows the progress of the channel signal processed by the radar signal processing method by the radar signal processing apparatus which concerns on Embodiment 1. FIG. 図４Ａは、実施の形態１に係るレーダ信号処理装置の機能を実現するハードウェア構成を示すブロック図である。図４Ｂは、実施の形態１に係るレーダ信号処理装置の機能を実現するソフトウェアを実行するハードウェア構成を示すブロック図である。FIG. 4A is a block diagram showing a hardware configuration that realizes the functions of the radar signal processing device according to the first embodiment. FIG. 4B is a block diagram showing a hardware configuration for executing software that realizes the functions of the radar signal processing device according to the first embodiment.
　以下、本開示をより詳細に説明するため、本開示を実施するための形態について、添付の図面に従って説明する。
実施の形態１．
　図１は、実施の形態１に係るレーダ信号処理装置１００の構成を示すブロック図である。図１が示すように、レーダ信号処理装置１００は、電力インバランス補正部１、高速フーリエ変換部２、ドップラー周波数領域帯域制限部３、逆高速フーリエ変換部４、ヒット領域帯域制限部５、インバランス補正部６、サブアパーチャー分割部９、復元アルゴリズム部１０、画像再生部１１、及びサブアパーチャー結合部１２を備えている。 Hereinafter, in order to explain the present disclosure in more detail, a mode for carrying out the present disclosure will be described with reference to the accompanying drawings.
Embodiment 1.
FIG. 1 is a block diagram showing a configuration of a radar signal processing device 100 according to the first embodiment. As shown in FIG. 1, the radar signal processing device 100 includes a power imbalance correction unit 1, a fast Fourier transform unit 2, a Doppler frequency domain band limiting unit 3, an inverse fast Fourier transform unit 4, a hit region band limiting unit 5, and an in. It includes a balance correction unit 6, a sub-aperture division unit 9, a restoration algorithm unit 10, an image reproduction unit 11, and a sub-aperture coupling unit 12.
　電力インバランス補正部１は、マルチチャネルＳＡＲによる観測によって得られた複数のチャネル信号（生データ）に対して、電力インバランス補正を行う。電力インバランス補正部１は、電力インバランス補正を行った複数のチャネル信号を高速フーリエ変換部２に出力する。 The power imbalance correction unit 1 corrects the power imbalance for a plurality of channel signals (raw data) obtained by observation by the multi-channel SAR. The power imbalance correction unit 1 outputs a plurality of channel signals that have undergone power imbalance correction to the fast Fourier transform unit 2.
　なお、本明細書において、「複数のチャネル信号」は、それぞれ、マルチチャネルＳＡＲにおける複数のチャネルのうちの対応するチャネルから得られた信号を意味する。また、本明細書において、「電力インバランス補正」は、チャネルの相違に伴って生じるチャネル信号間の電力のずれ量を補正することを意味する。実施の形態１では、マルチチャネルＳＡＲによる観測は、スライディングスポット観測である。なお、実施の形態１では、マルチチャネルＳＡＲによる観測がスライディングスポット観測である構成について説明するが、マルチチャネルＳＡＲによる観測は、例えば、フルスポットライト観測等であってもよい。 In the present specification, the "plurality of channel signals" means signals obtained from the corresponding channels among the plurality of channels in the multi-channel SAR, respectively. Further, in the present specification, "power imbalance correction" means to correct the amount of power deviation between channel signals caused by a channel difference. In the first embodiment, the observation by the multi-channel SAR is a sliding spot observation. In the first embodiment, the configuration in which the observation by the multi-channel SAR is the sliding spot observation will be described, but the observation by the multi-channel SAR may be, for example, a full spotlight observation or the like.
　高速フーリエ変換部２（ドップラー周波数変換部）は、マルチチャネルＳＡＲによる観測によって得られた複数のチャネル信号に対して、それぞれ、ドップラー周波数変換を行う。換言すれば、高速フーリエ変換部２（ドップラー周波数変換部）は、マルチチャネルＳＡＲによる観測によって得られた複数のチャネル信号に対して、それぞれ、高速フーリエ変換を行うことによりドップラー周波数領域の信号に変換する。より詳細には、実施の形態１では、高速フーリエ変換部２は、電力インバランス補正部１が電力インバランス補正を行った複数のチャネル信号に対して、それぞれ、ドップラー周波数変換を行う。高速フーリエ変換部２は、ドップラー周波数変換を行った複数のチャネル信号をドップラー周波数領域帯域制限部３に出力する。 The fast Fourier transform unit 2 (Doppler frequency conversion unit) performs Doppler frequency conversion for each of a plurality of channel signals obtained by observation by the multi-channel SAR. In other words, the fast Fourier transform unit 2 (Doppler frequency transform unit) converts a plurality of channel signals obtained by observation by the multi-channel SAR into signals in the Doppler frequency domain by performing a fast Fourier transform. do. More specifically, in the first embodiment, the fast Fourier transform unit 2 performs Doppler frequency conversion for each of the plurality of channel signals for which the power imbalance correction unit 1 has performed the power imbalance correction. The fast Fourier transform unit 2 outputs a plurality of channel signals that have undergone Doppler frequency conversion to the Doppler frequency domain band limiting unit 3.
　ドップラー周波数領域帯域制限部３（バンドパスフィルタ）は、高速フーリエ変換部２がドップラー周波数変換を行った複数のチャネル信号に対して、それぞれ、ドップラー周波数領域における帯域制限を行う。より詳細には、実施の形態１では、ドップラー周波数領域帯域制限部３は、ドップラー周波数領域における帯域制限によって、ドップラー中心周波数を中心とした帯域のチャネル信号を抽出する。ドップラー周波数領域帯域制限部３は、ドップラー周波数領域における帯域制限を行った複数のチャネル信号を逆高速フーリエ変換部４に出力する。 The Doppler frequency domain band limiting unit 3 (bandpass filter) limits the band in the Doppler frequency domain for each of the plurality of channel signals for which the fast Fourier transform unit 2 has undergone the Doppler frequency conversion. More specifically, in the first embodiment, the Doppler frequency domain band limiting unit 3 extracts a channel signal in a band centered on the Doppler center frequency by band limiting in the Doppler frequency domain. The Doppler frequency domain band limiting unit 3 outputs a plurality of channel signals band-limited in the Doppler frequency domain to the inverse fast Fourier transform unit 4.
　逆高速フーリエ変換部４（逆ドップラー周波数変換部）は、ドップラー周波数領域帯域制限部３がドップラー周波数領域における帯域制限を行った複数のチャネル信号に対して、それぞれ、逆ドップラー周波数変換を行う。換言すれば、逆高速フーリエ変換部４は、ドップラー周波数領域帯域制限部３がドップラー周波数領域における帯域制限を行った複数のチャネル信号に対して、それぞれ、逆高速フーリエ変換を行うことにより、高速フーリエ変換部２が高速フーリエ変換を行う前の元の時間領域の信号に変換する。逆高速フーリエ変換部４は、逆ドップラー周波数変換を行った複数のチャネル信号をヒット領域帯域制限部５に出力する。 The inverse fast Fourier transform unit 4 (inverse Doppler frequency converter) performs inverse Doppler frequency conversion for each of a plurality of channel signals for which the Doppler frequency domain band limiting unit 3 has band-limited in the Doppler frequency domain. In other words, the inverse fast Fourier transform unit 4 performs an inverse fast Fourier transform on each of a plurality of channel signals for which the Doppler frequency domain band limiting unit 3 has band-limited in the Doppler frequency domain, thereby performing a fast Fourier transform. The transforming unit 2 converts the signal into the signal in the original time domain before performing the fast Fourier transform. The inverse fast Fourier transform unit 4 outputs a plurality of channel signals subjected to the inverse Doppler frequency conversion to the hit region band limiting unit 5.
　ヒット領域帯域制限部５（バンドパスフィルタ）は、マルチチャネルＳＡＲによる観測によって得られた複数のチャネル信号に対して、それぞれ、ヒット領域における帯域制限を行う。より詳細には、実施の形態１では、ヒット領域帯域制限部５は、逆高速フーリエ変換部４が逆ドップラー周波数変換を行った複数のチャネル信号に対して、それぞれ、ヒット領域における帯域制限を行う。さらに詳細には、実施の形態１では、ヒット領域帯域制限部５は、ヒット領域における帯域制限によって、ヒット中心を中心とした帯域のチャネル信号を抽出する。ヒット領域帯域制限部５は、ヒット領域における帯域制限を行った複数のチャネル信号をインバランス補正部６に出力する。 The hit area band limiting unit 5 (bandpass filter) limits the band in the hit area for each of the plurality of channel signals obtained by the observation by the multi-channel SAR. More specifically, in the first embodiment, the hit region band limiting unit 5 limits the bandwidth in the hit region for each of the plurality of channel signals subjected to the inverse Doppler frequency conversion by the inverse fast Fourier transform unit 4. .. More specifically, in the first embodiment, the hit region band limiting unit 5 extracts a channel signal in a band centered on the hit center by band limiting in the hit region. The hit area band limiting unit 5 outputs a plurality of channel signals for which the band is limited in the hit area to the imbalance correction unit 6.
　インバランス補正部６は、ヒット領域帯域制限部５がヒット領域における帯域制限を行った複数のチャネル信号に基づいて、チャネル信号間のインバランス補正を行う。より詳細には、実施の形態１では、インバランス補正部６は、チャネル信号間のインバランス補正として、位相インバランスの補正を行う。インバランス補正部６は、インバランス補正を行った複数のチャネル信号をサブアパーチャー分割部９に出力する。 The imbalance correction unit 6 performs imbalance correction between channel signals based on a plurality of channel signals for which the hit region band limiting unit 5 has band-limited in the hit region. More specifically, in the first embodiment, the imbalance correction unit 6 corrects the phase imbalance as the imbalance correction between the channel signals. The imbalance correction unit 6 outputs a plurality of channel signals for which imbalance correction has been performed to the sub-aperture division unit 9.
　なお、本明細書において、「位相インバランス」は、チャネルの相違に伴って生じるチャネル信号間の位相のずれ量を意味する。実施の形態１では、インバランス補正部６がインバランス補正として位相インバランスの補正を行う構成について説明するが、インバランス補正部６は、チャネル信号間のインバランス補正として、レンジサンプルずれの補正を行ってもよい。 In the present specification, "phase imbalance" means the amount of phase shift between channel signals caused by the difference in channels. In the first embodiment, the configuration in which the imbalance correction unit 6 corrects the phase imbalance as the imbalance correction will be described, but the imbalance correction unit 6 corrects the range sample deviation as the imbalance correction between the channel signals. May be done.
　さらに詳細には、実施の形態１では、インバランス補正部６は、ドップラー中心周波数推定部７、及び位相インバランス補正部８を備えている。
　ドップラー中心周波数推定部７は、ヒット領域帯域制限部５がヒット領域における帯域制限を行った複数のチャネル信号のドップラー中心周波数を推定する。ドップラー中心周波数推定部７は、推定したドップラー中心周波数を位相インバランス補正部８に出力する。 More specifically, in the first embodiment, the imbalance correction unit 6 includes a Doppler center frequency estimation unit 7 and a phase imbalance correction unit 8.
The Doppler center frequency estimation unit 7 estimates the Doppler center frequencies of a plurality of channel signals for which the hit region band limiting unit 5 has band-limited in the hit region. The Doppler center frequency estimation unit 7 outputs the estimated Doppler center frequency to the phase imbalance correction unit 8.
　位相インバランス補正部８は、ドップラー中心周波数推定部７が推定したドップラー中心周波数に基づいて、ヒット領域帯域制限部５がヒット領域における帯域制限を行った複数のチャネル信号に基づいて、チャネル信号間の位相インバランスの補正を行う。位相インバランス補正部８は、位相インバランスの補正を行った複数のチャネル信号をサブアパーチャー分割部９に出力する。 The phase imbalance correction unit 8 is based on the Doppler center frequency estimated by the Doppler center frequency estimation unit 7, and is based on a plurality of channel signals for which the hit region band limiting unit 5 has band-limited in the hit region. The phase imbalance of is corrected. The phase imbalance correction unit 8 outputs a plurality of channel signals for which the phase imbalance has been corrected to the sub-aperture division unit 9.
　サブアパーチャー分割部９は、インバランス補正部６がインバランス補正を行った複数のチャネル信号に対して、サブアパーチャー分割を行う。より詳細には、実施の形態１では、サブアパーチャー分割部９は、インバランス補正部６の位相インバランス補正部８が位相インバランスの補正を行った複数のチャネル信号に対して、サブアパーチャー分割を行う。サブアパーチャー分割部９は、サブアパーチャー分割を行った複数のチャネル信号を復元アルゴリズム部１０に出力する。 The sub-aperture division unit 9 performs sub-aperture division for a plurality of channel signals for which the imbalance correction unit 6 has performed imbalance correction. More specifically, in the first embodiment, the sub-aperture division unit 9 divides the sub-aperture into a plurality of channel signals for which the phase imbalance correction unit 8 of the imbalance correction unit 6 has corrected the phase imbalance. I do. The sub-aperture division unit 9 outputs a plurality of channel signals obtained by sub-aperture division to the restoration algorithm unit 10.
　復元アルゴリズム部１０は、サブアパーチャー分割部９がサブアパーチャー分割を行った複数のチャネル信号に対して、復元アルゴリズムを行う。復元アルゴリズム部１０は、復元アルゴリズムを行った複数のチャネル信号を画像再生部１１に出力する。 The restoration algorithm unit 10 performs a restoration algorithm on a plurality of channel signals for which the sub-aperture division unit 9 has performed sub-aperture division. The restoration algorithm unit 10 outputs a plurality of channel signals subjected to the restoration algorithm to the image reproduction unit 11.
　画像再生部１１は、復元アルゴリズム部１０が復元アルゴリズムを行った複数のチャネル信号に対して、画像再生を行う。画像再生部１１は、画像再生を行った複数のチャネル信号をサブアパーチャー結合部１２に出力する。 The image reproduction unit 11 reproduces an image on a plurality of channel signals for which the restoration algorithm unit 10 has performed the restoration algorithm. The image reproduction unit 11 outputs a plurality of channel signals for which image reproduction has been performed to the sub-aperture coupling unit 12.
　サブアパーチャー結合部１２は、画像再生部１１が画像再生を行った複数のチャネル信号に対してサブアパーチャー結合を行うことによりＳＡＲ画像を生成する。例えば、サブアパーチャー結合部１２が生成したＳＡＲ画像は、図示しないディスプレイによって表示される。 The sub-aperture coupling unit 12 generates a SAR image by performing sub-aperture coupling on a plurality of channel signals for which the image reproduction unit 11 has reproduced an image. For example, the SAR image generated by the sub-aperture coupling portion 12 is displayed by a display (not shown).
　以下で、実施の形態１に係るレーダ信号処理装置１００の動作について図面を参照して説明する。図２は、実施の形態１に係るレーダ信号処理装置１００によるレーダ信号処理方法を示すフローチャートである。なお、以下で説明する各ステップの前に、レーダ信号処理装置１００は、マルチチャネルＳＡＲによる観測によって得られた複数のチャネル信号を取得したものとする。 Hereinafter, the operation of the radar signal processing device 100 according to the first embodiment will be described with reference to the drawings. FIG. 2 is a flowchart showing a radar signal processing method by the radar signal processing device 100 according to the first embodiment. Before each step described below, it is assumed that the radar signal processing device 100 has acquired a plurality of channel signals obtained by observation by the multi-channel SAR.
　図２が示すように、電力インバランス補正部１は、マルチチャネルＳＡＲによる観測によって得られた複数のチャネル信号に対して、電力インバランス補正を行う（ステップＳＴ１）。電力インバランス補正部１は、電力インバランス補正を行った複数のチャネル信号を高速フーリエ変換部２に出力する。 As shown in FIG. 2, the power imbalance correction unit 1 performs power imbalance correction on a plurality of channel signals obtained by observation by the multi-channel SAR (step ST1). The power imbalance correction unit 1 outputs a plurality of channel signals that have undergone power imbalance correction to the fast Fourier transform unit 2.
　次に、高速フーリエ変換部２は、電力インバランス補正部１が電力インバランス補正を行った複数のチャネル信号に対して、それぞれ、ドップラー周波数変換を行う（ステップＳＴ２）。高速フーリエ変換部２は、ドップラー周波数変換を行った複数のチャネル信号をドップラー周波数領域帯域制限部３に出力する。 Next, the fast Fourier transform unit 2 performs Doppler frequency conversion for each of the plurality of channel signals for which the power imbalance correction unit 1 has performed the power imbalance correction (step ST2). The fast Fourier transform unit 2 outputs a plurality of channel signals that have undergone Doppler frequency conversion to the Doppler frequency domain band limiting unit 3.
　次に、ドップラー周波数領域帯域制限部３は、高速フーリエ変換部２がドップラー周波数変換を行った複数のチャネル信号に対して、それぞれ、ドップラー周波数領域における帯域制限を行う（ステップＳＴ３）。ドップラー周波数領域帯域制限部３は、ドップラー周波数領域における帯域制限を行った複数のチャネル信号を逆高速フーリエ変換部４に出力する。 Next, the Doppler frequency domain band limiting unit 3 limits the band in the Doppler frequency domain for each of the plurality of channel signals subjected to the Doppler frequency conversion by the fast Fourier transform unit 2 (step ST3). The Doppler frequency domain band limiting unit 3 outputs a plurality of channel signals band-limited in the Doppler frequency domain to the inverse fast Fourier transform unit 4.
　次に、逆高速フーリエ変換部４は、ドップラー周波数領域帯域制限部３がドップラー周波数領域における帯域制限を行った複数のチャネル信号に対して、それぞれ、逆ドップラー周波数変換を行う（ステップＳＴ４）。逆高速フーリエ変換部４は、逆ドップラー周波数変換を行った複数のチャネル信号をヒット領域帯域制限部５に出力する。 Next, the inverse fast Fourier transform unit 4 performs inverse Doppler frequency conversion for each of the plurality of channel signals for which the Doppler frequency domain band limiting unit 3 has band-limited in the Doppler frequency domain (step ST4). The inverse fast Fourier transform unit 4 outputs a plurality of channel signals subjected to the inverse Doppler frequency conversion to the hit region band limiting unit 5.
　次に、ヒット領域帯域制限部５は、逆高速フーリエ変換部４が逆ドップラー周波数変換を行った複数のチャネル信号に対して、それぞれ、ヒット領域における帯域制限を行う（ステップＳＴ５）。ヒット領域帯域制限部５は、ヒット領域における帯域制限を行った複数のチャネル信号をインバランス補正部６に出力する。 Next, the hit region band limiting unit 5 limits the bandwidth in the hit region for each of the plurality of channel signals for which the inverse fast Fourier transform unit 4 has undergone the inverse Doppler frequency conversion (step ST5). The hit area band limiting unit 5 outputs a plurality of channel signals for which the band is limited in the hit area to the imbalance correction unit 6.
　次に、インバランス補正部６のドップラー中心周波数推定部７は、ヒット領域帯域制限部５がヒット領域における帯域制限を行った複数のチャネル信号のドップラー中心周波数を推定する（ステップＳＴ６）。ドップラー中心周波数推定部７は、推定したドップラー中心周波数を位相インバランス補正部８に出力する。 Next, the Doppler center frequency estimation unit 7 of the imbalance correction unit 6 estimates the Doppler center frequency of a plurality of channel signals for which the hit region band limiting unit 5 has band-limited in the hit region (step ST6). The Doppler center frequency estimation unit 7 outputs the estimated Doppler center frequency to the phase imbalance correction unit 8.
　次に、インバランス補正部６の位相インバランス補正部８は、ドップラー中心周波数推定部７が推定したドップラー中心周波数に基づいて、チャネル信号間の位相インバランスの補正を行う（ステップＳＴ７）。位相インバランス補正部８は、位相インバランスの補正を行った複数のチャネル信号をサブアパーチャー分割部９に出力する。 Next, the phase imbalance correction unit 8 of the imbalance correction unit 6 corrects the phase imbalance between the channel signals based on the Doppler center frequency estimated by the Doppler center frequency estimation unit 7 (step ST7). The phase imbalance correction unit 8 outputs a plurality of channel signals for which the phase imbalance has been corrected to the sub-aperture division unit 9.
　次に、サブアパーチャー分割部９は、インバランス補正部６が位相インバランスの補正を行った複数のチャネル信号に対して、サブアパーチャー分割を行う（ステップＳＴ８）。サブアパーチャー分割部９は、サブアパーチャー分割を行った複数のチャネル信号を復元アルゴリズム部１０に出力する。 Next, the sub-aperture division unit 9 performs sub-aperture division for a plurality of channel signals for which the imbalance correction unit 6 has corrected the phase imbalance (step ST8). The sub-aperture division unit 9 outputs a plurality of channel signals obtained by sub-aperture division to the restoration algorithm unit 10.
　次に、復元アルゴリズム部１０は、サブアパーチャー分割部９がサブアパーチャー分割を行った複数のチャネル信号に対して、復元アルゴリズムを行う（ステップＳＴ９）。復元アルゴリズム部１０は、復元アルゴリズムを行った複数のチャネル信号を画像再生部１１に出力する。 Next, the restoration algorithm unit 10 performs a restoration algorithm on a plurality of channel signals for which the sub-aperture division unit 9 has undergone sub-aperture division (step ST9). The restoration algorithm unit 10 outputs a plurality of channel signals subjected to the restoration algorithm to the image reproduction unit 11.
　次に、画像再生部１１は、復元アルゴリズム部１０が復元アルゴリズムを行った複数のチャネル信号に対して、画像再生を行う（ステップＳＴ１０）。画像再生部１１は、画像再生を行った複数のチャネル信号をサブアパーチャー結合部１２に出力する。 Next, the image reproduction unit 11 reproduces an image on a plurality of channel signals for which the restoration algorithm unit 10 has performed the restoration algorithm (step ST10). The image reproduction unit 11 outputs a plurality of channel signals for which image reproduction has been performed to the sub-aperture coupling unit 12.
　サブアパーチャー結合部１２は、画像再生部１１が画像再生を行った複数のチャネル信号に対してサブアパーチャー結合を行うことによりＳＡＲ画像を生成する（ステップＳＴ１１）。例えば、サブアパーチャー結合部１２がステップＳＴ１１で生成したＳＡＲ画像は、図示しないディスプレイによって表示される。 The sub-aperture coupling unit 12 generates a SAR image by performing sub-aperture coupling on a plurality of channel signals for which the image reproduction unit 11 has reproduced an image (step ST11). For example, the SAR image generated by the sub-aperture coupling unit 12 in step ST11 is displayed by a display (not shown).
　以下で、実施の形態１に係るレーダ信号処理装置１００によるレーダ信号処理方法の具体例について図面を参照して説明する。図３は、実施の形態１に係るレーダ信号処理装置１００によるレーダ信号処理方法によって処理されたチャネル信号の途中経過を示す図である。 Hereinafter, a specific example of the radar signal processing method by the radar signal processing device 100 according to the first embodiment will be described with reference to the drawings. FIG. 3 is a diagram showing the progress of a channel signal processed by the radar signal processing method by the radar signal processing device 100 according to the first embodiment.
　当該具体例では、マルチチャネルＳＡＲによる観測によって得られた複数のチャネル信号は、２チャネルのスライディングスポットライト観測で得られた信号である。レーダ信号処理装置１００によって処理される前の第１のチャネル信号（チャネル０の信号）をｓ０（τ，η）とし、第２のチャネル信号（チャネル１の信号）をｓ１（τ，η）とする。τは、レンジ時間であり、ηは、ヒットである。なお、以下では、第１のチャネル信号を基準チャネルとする。 In the specific example, the plurality of channel signals obtained by the observation by the multi-channel SAR are the signals obtained by the two-channel sliding spotlight observation. The first channel signal (channel 0 signal) before being processed by the radar signal processing device 100 is s 0 (τ, η), and the second channel signal (channel 1 signal) is s 1 (τ, η). ). τ is the range time and η is a hit. In the following, the first channel signal will be used as a reference channel.
　当該具体例では、上述のステップＳＴ１において、電力インバランス補正部１は、第１のチャネル信号ｓ０（τ，η）、及び第２のチャネル信号ｓ１（τ，η）に対して、以下で説明する方法に従って電力インバランス補正を行う（例えば、非特許文献J. H. Kim, M. Younis, P. P. Iraola, M. Gebele, and G. Krieger, “First spaceborne demonstration of digital beamforming for azimuth ambiguity suppression”, IEEE Trans. Geosci. Remote Sens., vol.51, no.1, pp.579-590, Jan., 2013を参照）。 In the specific example, in the above-mentioned step ST1, the power imbalance correction unit 1 has the following with respect to the first channel signal s 0 (τ, η) and the second channel signal s 1 (τ, η). Power imbalance correction is performed according to the method described in (For example, Non-Patent Document J. H. Kim, M. Younis, P. P. Iraola, M. Gebele, and G. Krieger, “First spaceborne demonstration of digital beamforming for azimuth ambiguity suppression”, IEEE. See Trans. Geosci. Remote Sens., Vol.51, no.1, pp.579-590, Jan., 2013).
　まず、電力インバランス補正部１は、レンジ周波数領域で電力インバランスの補正を行うために、第１のチャネル信号ｓ０（τ，η）及び第２のチャネル信号ｓ１（τ，η）に対してレンジ周波数変換を行う。これにより、電力インバランス補正部１は、レンジ周波数をｆｒとしてＳ０（ｆｒ，η）、及びＳ１（ｆｒ，η）を得る。 First, the power imbalance correction unit 1 uses the first channel signal s 0 (τ, η) and the second channel signal s 1 (τ, η) to correct the power imbalance in the range frequency region. On the other hand, range frequency conversion is performed. As a result, the power imbalance correction unit 1 obtains S 0 ( fr , η) and S 1 ( fr , η) with the range frequency as fr .
　次に、電力インバランス補正部１は、第１のチャネル信号で発生する雑音電力をσ０ ２とし、第２のチャネル信号で発生する雑音電力をσ１ ２として、以下の式（１）に従って、電力（振幅）インバランスの補正係数α（ｆｒ）を算出する。

Figure JPOXMLDOC01-appb-I000001
Next, the power imbalance correction unit 1 sets the noise power generated by the first channel signal as σ 0 2 , and the noise power generated by the second channel signal as σ 1 2 , according to the following equation (1). , The correction coefficient α ( fr ) of the power (amplitude) imbalance is calculated.

Figure JPOXMLDOC01-appb-I000001
　式（１）において、Ｅη（｜Ｓ０（ｆｒ，η）｜２）は、｜Ｓ０（ｆｒ，η）｜２のヒット方向の平均を示し、Ｅη（｜Ｓ１（ｆｒ，η）｜２）は、｜Ｓ１（ｆｒ，η）｜２のヒット方向の平均を示す。ただし、雑音電力が未知である場合には、σ０ ２＝σ１ ２＝０としてもよい。 In the equation (1), E η (| S 0 ( fr , η) | 2 ) indicates the average of | S 0 ( fr , η) | 2 in the hit direction, and E η (| S 1 (f)). r , η) | 2 ) indicates the average of | S 1 ( fr , η) | 2 in the hit direction. However, when the noise power is unknown, σ 0 2 = σ 1 2 = 0 may be set.
　次に、電力インバランス補正部１は、算出した補正係数α（ｆｒ）に基づいて、以下の式（２）に従って、Ｓ１（ｆｒ，η）の振幅を補正する。

Figure JPOXMLDOC01-appb-I000002
Next, the power imbalance correction unit 1 corrects the amplitude of S 1 ( fr , η ) according to the following equation (2) based on the calculated correction coefficient α (fr).

Figure JPOXMLDOC01-appb-I000002
　次に、電力インバランス補正部１は、式（２）により得られたＳ１’（ｆｒ，η）に対してレンジ時間変換を行うことにより、電力インバランスの補正が行われた第２のチャネル信号ｓ１’（τ，η）を得る。
　なお、電力インバランス補正部１は、電力インバランスを補正する方法として、当該具体例の方法以外の方法を用いてもよい。 Next, the power imbalance correction unit 1 corrects the power imbalance by performing range time conversion on S 1 '( fr , η) obtained by the equation (2). Channel signal s 1 '(τ, η) of.
The power imbalance correction unit 1 may use a method other than the method of the specific example as a method of correcting the power imbalance.
　図３のＡは、ステップＳＴ１の処理後の第１のチャネル信号ｓ０（τ，η）のグラフを示す。図３のＡにおける縦軸は、ヒットを示し、横軸は、レンジを示す。図３のＡが示すように、７点の点像の生データがヒット－レンジ空間に多重化されている。 FIG. 3A shows a graph of the first channel signal s 0 (τ, η) after the processing of step ST1. In FIG. 3, the vertical axis in A indicates a hit, and the horizontal axis indicates a range. As shown by A in FIG. 3, the raw data of the seven point images are multiplexed in the hit-range space.
　次に、上述のステップＳＴ２において、高速フーリエ変換部２は、第１のチャネル信号ｓ０（τ，η）及び第２のチャネル信号ｓ１’（τ，η）に対して、それぞれ、ドップラー周波数変換を行う。図３のＢは、ステップＳＴ２の処理後の第１のチャネル信号のグラフを示す。図３のＢにおける縦軸は、ドップラー周波数を示し、横軸は、レンジを示す。図３のＢが示すように、第１のチャネル信号ｓ０（τ，η）は、アジマスアンビギュイティが多重化している。なお、図示しないが、第２のチャネル信号ｓ１’（τ，η）についても同様に、アジマスアンビギュイティが多重化している。 Next, in step ST2 described above, the fast Fourier transform unit 2 has a Doppler frequency with respect to the first channel signal s 0 (τ, η) and the second channel signal s 1 '(τ, η), respectively. Perform the conversion. FIG. 3B shows a graph of the first channel signal after the processing of step ST2. In FIG. 3, the vertical axis in B indicates the Doppler frequency, and the horizontal axis indicates the range. As shown by B in FIG. 3, the first channel signal s 0 (τ, η) is multiplexed with azimuth ambiguity. Although not shown, the azimuth ambiguity is similarly multiplexed for the second channel signal s 1 '(τ, η).
　次に、上述のステップＳＴ３において、ドップラー周波数領域帯域制限部３は、ステップＳＴ２の処理によって得られた第１のチャネル信号及び第２のチャネル信号の各ドップラー周波数成分に対して、ドップラー周波数領域における帯域制限を行う。図３のＣは、ステップＳＴ３の処理後の第１のチャネル信号のグラフを示す。図３のＣにおける縦軸は、ドップラー周波数を示し、横軸は、レンジを示す。図３のＣが示すように、ステップＳＴ３の処理によりドップラー中心周波数付近の信号が抽出される。なお、図示しないが、第２のチャネル信号ｓ１’（τ，η）についても同様に、ステップＳＴ３の処理によりドップラー中心周波数付近の信号が抽出される。 Next, in step ST3 described above, the Doppler frequency domain band limiting unit 3 in the Doppler frequency domain for each Doppler frequency component of the first channel signal and the second channel signal obtained by the processing of step ST2. Bandwidth limitation. FIG. 3C shows a graph of the first channel signal after the processing of step ST3. The vertical axis in C in FIG. 3 indicates the Doppler frequency, and the horizontal axis indicates the range. As shown by C in FIG. 3, a signal near the Doppler center frequency is extracted by the process of step ST3. Although not shown, for the second channel signal s 1 '(τ, η), a signal near the Doppler center frequency is similarly extracted by the process of step ST3.
　次に、上述のステップＳＴ４において、逆高速フーリエ変換部４は、ステップＳＴ３の処理によって得られた第１のチャネル信号及び第２のチャネル信号に対して逆ドップラー周波数変換を行う。図３のＤは、ステップＳＴ４の処理後の第１のチャネル信号のグラフを示す。図３のＤにおける縦軸は、ヒットを示し、横軸は、レンジを示す。図３のＤが示すように、ステップＳＴ４の処理後の第１のチャネル信号ｓ０（τ，η）は、信号が離散的に分散されている。なお、図示しないが、ステップＳＴ４の処理後の第２のチャネル信号ｓ１’（τ，η）についても同様に、信号が離散的に分散されている。 Next, in step ST4 described above, the inverse fast Fourier transform unit 4 performs inverse Doppler frequency conversion on the first channel signal and the second channel signal obtained by the processing of step ST3. FIG. 3D shows a graph of the first channel signal after the processing of step ST4. The vertical axis in D in FIG. 3 indicates a hit, and the horizontal axis indicates a range. As shown by D in FIG. 3, in the first channel signal s 0 (τ, η) after the processing of step ST4, the signals are discretely dispersed. Although not shown, the signals of the second channel signal s 1 '(τ, η) after the processing of step ST4 are also discretely dispersed.
　次に、上述のステップＳＴ５において、ヒット領域帯域制限部５は、ステップＳＴ４の処理によって得られた第１のチャネル信号及び第２のチャネル信号の各ヒット－レンジ成分に対して、ヒット領域での帯域制限を行う。図３のＥは、ステップＳＴ５の処理後の第１のチャネル信号のグラフを示す。図３のＥにおける縦軸は、ヒットを示し、横軸は、レンジを示す。図３のＥが示すように、アジマスアンビギュイティを抑圧することによりアジマスアンビギュイティが分離された信号が得られる。なお、図示しないが、第２のチャネル信号ｓ１’（τ，η）についても同様に、アジマスアンビギュイティが分離された信号が得られる。以下では、ステップＳＴ５の処理によって得られた第１のチャネル信号を、ｓ ０（τ，η）とし、第２のチャネル信号をｓ １’（τ，η）とする。 Next, in step ST5 described above, the hit region band limiting unit 5 has a hit region for each hit-range component of the first channel signal and the second channel signal obtained by the processing of step ST4. Bandwidth limitation. FIG. 3E shows a graph of the first channel signal after the processing of step ST5. The vertical axis in E in FIG. 3 indicates a hit, and the horizontal axis indicates a range. As shown by E in FIG. 3, by suppressing the azimuth ambiguity, a signal from which the azimuth ambiguity is separated is obtained. Although not shown, a signal from which the azimuth ambiguity is separated can be obtained similarly for the second channel signal s 1 '(τ, η). In the following, the first channel signal obtained by the process of step ST5 is s 0 (τ, η), and the second channel signal is s 1 '(τ, η).
　次に、上述のステップＳＴ６及びステップＳＴ７において、インバランス補正部６は、ステップＳＴ５の処理によって得られた第１のチャネル信号ｓ ０（τ，η）及び第２のチャネル信号ｓ １’（τ，η）に基づいて、以下で説明する方法に従って、チャネル信号間の位相インバランスの補正を行う（例えば、H. Fan, Z. Zhang, and R. Wang, “phase mismatch calibration for multichannel sliding spotlight SAR imaging with extended azimuth cross correlation”, IGARSS 2019を参照）。 Next, in step ST6 and step ST7 described above, the imbalance correction unit 6 performs the first channel signal s 0 (τ, η) and the second channel signal s 1 '(τ) obtained by the processing of step ST5. , Η), and corrects the phase imbalance between the channel signals according to the method described below (eg, H. Fan, Z. Zhang, and R. Wang, “phase mismatch calibration for multichannel sliding spotlight SAR). imaging with extended azimuth cross correlation ”, see IGARSS 2019).
　まず、上述のステップＳＴ６において、インバランス補正部６のドップラー中心周波数推定部７は、第１のチャネル信号ｓ ０（τ，η）及び第２のチャネル信号ｓ １’（τ，η）に基づいて、以下の式（３）及び式（４）に従って、２つの干渉データＣ１，０（τ）及びＣ０，１（τ）を算出する。

Figure JPOXMLDOC01-appb-I000003

Figure JPOXMLDOC01-appb-I000004
First, in step ST6 described above, the Doppler center frequency estimation unit 7 of the imbalance correction unit 6 is based on the first channel signal s 0 (τ, η) and the second channel signal s 1 '(τ, η). Then, two interference data C 1,0 (τ) and C 0,1 (τ) are calculated according to the following equations (3) and (4).

Figure JPOXMLDOC01-appb-I000003

Figure JPOXMLDOC01-appb-I000004
　式（４）において、ＰＲＦは、パルス繰り返し周波数であり、チャネル信号内のアジマス方向の１サンプルずれに相当する。式（３）及び式（４）において、Ｅη（　）は、上述の通り、括弧内の数式のヒット方向の平均を示す。 In equation (4), the PRF is the pulse repetition frequency and corresponds to one sample shift in the azimuth direction in the channel signal. In equations (3) and (4), E η () indicates the average of the equations in parentheses in the hit direction, as described above.
　次に、ドップラー中心周波数推定部７は、干渉データＣ１，０（τ）及びＣ０，１（τ）の両者の積Ｃ１，０（τ）Ｃ０，１（τ）を算出することにより、ｓ １’（τ，η）に含まれる位相インバランスを相殺する。ドップラー中心周波数をｆｄｃ（τ）とすると，以下の式（５）の関係が得られる。

Figure JPOXMLDOC01-appb-I000005
Next, the Doppler center frequency estimation unit 7 calculates the product C 1,0 (τ) C 0,1 (τ) of both the interference data C 1,0 (τ) and C 0,1 (τ). Therefore, the phase imbalance contained in s 1 '(τ, η) is offset. Assuming that the Doppler center frequency is f dc (τ), the relationship of the following equation (5) is obtained.

Figure JPOXMLDOC01-appb-I000005
　ドップラー中心周波数推定部７は、算出したＣ１，０（τ）Ｃ０，１（τ）に基づいて、以下の式（６）に従って、ドップラー中心周波数ｆｄｃ（τ）を算出する。

Figure JPOXMLDOC01-appb-I000006
The Doppler center frequency estimation unit 7 calculates the Doppler center frequency f dc (τ) based on the calculated C 1,0 (τ) C 0,1 (τ) according to the following equation (6).

Figure JPOXMLDOC01-appb-I000006
　次に、上述のステップＳＴ７において、インバランス補正部６の位相インバランス補正部８は、ドップラー中心周波数推定部７が算出したドップラー中心周波数ｆｄｃ（τ）に基づいて、以下の式（７）に従って、位相インバランスφ（τ）を算出する。

Figure JPOXMLDOC01-appb-I000007
　式（７）において、ｖｓは、プラットフォーム速度を示し、ｄは、２チャネルの受信位相中心間距離を示す。 Next, in step ST7 described above, the phase imbalance correction unit 8 of the imbalance correction unit 6 has the following equation (7) based on the Doppler center frequency f dc (τ) calculated by the Doppler center frequency estimation unit 7. The phase imbalance φ (τ) is calculated according to the above.

Figure JPOXMLDOC01-appb-I000007
In equation (7), vs represents the platform speed and d represents the distance between the reception phase centers of the two channels.
　次に、位相インバランス補正部８は、得られた位相インバランスφ（τ）に対して，重みを生成し，ヒット方向の期待値をとるように加重平均処理を行う。この処理により，推定値の誤差を低減する。より詳細には、まず、位相インバランス補正部８は、以下の式（８）に従って、｜ｓ ０（τ，η）｜のヒット方向の平均を算出する。なお、｜　｜は、括弧内の数式の絶対値を示す。

Figure JPOXMLDOC01-appb-I000008
Next, the phase imbalance correction unit 8 generates a weight for the obtained phase imbalance φ (τ) and performs a weighted averaging process so as to take an expected value in the hit direction. This process reduces the error in the estimated value. More specifically, first, the phase imbalance correction unit 8 calculates the average of | s 0 (τ, η) | in the hit direction according to the following equation (8). Note that || indicates the absolute value of the formula in parentheses.

Figure JPOXMLDOC01-appb-I000008
　次に、位相インバランス補正部８は、以下の式（９）に従って、加重平均をとり、位相インバランスφを算出する。

Figure JPOXMLDOC01-appb-I000009
　式（９）において、Ｅτ｛　｝は、括弧内の数式のレンジ時間方向の平均を示す。 Next, the phase imbalance correction unit 8 takes a weighted average according to the following equation (9) and calculates the phase imbalance φ .

Figure JPOXMLDOC01-appb-I000009
In equation (9), E τ {} indicates the average of the equations in parentheses in the range time direction.
　次に、位相インバランス補正部８は、算出した位相インバランスφに基づいて、以下の式（１０）に従って、チャネル信号間の位相インバランスの補正を行う。より詳細には、当該具体例では、位相インバランス補正部８は、算出した位相インバランスφに基づいて、以下の式（１０）に従って、上述の電力インバランス補正後の第２のチャネル信号ｓ１’（τ，η）に対して位相インバランスの補正を行う。

Figure JPOXMLDOC01-appb-I000010
　なお、インバランス補正部６は、位相インバランスを補正する方法として、当該具体例の方法以外の方法を用いてもよい。 Next, the phase imbalance correction unit 8 corrects the phase imbalance between the channel signals according to the following equation (10) based on the calculated phase imbalance φ . More specifically, in the specific example, the phase imbalance correction unit 8 has the second channel signal s after the power imbalance correction described above according to the following equation (10) based on the calculated phase imbalance φ . Correct the phase imbalance for 1 '(τ, η).

Figure JPOXMLDOC01-appb-I000010
The imbalance correction unit 6 may use a method other than the method of the specific example as a method of correcting the phase imbalance.
　次に、上述のステップＳＴ８において、サブアパーチャー分割部９は、ステップＳＴ７の処理後の第２のチャネル信号ｓ１’’（τ，η）、及び第１のチャネル信号ｓ０（τ，η）に対して、サブアパーチャー分割を行う（サブアパーチャー分割の方法については、例えば、非特許文献J. Mittermayer, R. Lord, and E. B¨oner,“Sliding spotlight SAR processing for TerraSAR-X using a new fomulation of the extended chirp scaling algorithm,” IGARSS2003, vol.3, p.1462-1464, 2003.を参照）。 Next, in step ST8 described above, the sub-aperture dividing unit 9 has the second channel signal s 1 '' (τ, η) and the first channel signal s 0 (τ, η) after the processing of step ST7. (For the method of sub-aperture division, for example, the non-patent document J. Mittermayer, R. Lord, and E. B ¨oner, “Sliding spotlight SAR processing for TerraSAR-X using a new” fomulation of the extended chirp scaling algorithm, ”IGARSS2003, vol.3, p.1462-1464, 2003.).
　次に、上述のステップＳＴ９において、復元アルゴリズム部１０は、サブアパーチャー分割部９がサブアパーチャー分割を行った第１のチャネル信号及び第２のチャネル信号に対して、復元アルゴリズムを行う（復元アルゴリズムの方法については、例えば、上述の非特許文献１を参照）。 Next, in step ST9 described above, the restoration algorithm unit 10 performs a restoration algorithm on the first channel signal and the second channel signal to which the sub-aperture division unit 9 has performed the sub-aperture division (reconstruction algorithm). For the method, see, for example, Non-Patent Document 1 described above).
　次に、上述のステップＳＴ１０において、画像再生部１１は、復元アルゴリズム部１０が復元アルゴリズムを行った第１のチャネル信号及び第２のチャネル信号に対して、画像再生を行う。なお、画像再生方法の例として、拡張チャープスケーリング等が挙げられる（例えば、上述の非特許文献J. Mittermayer, R. Lord, and E. B¨oner,“Sliding spotlight SAR processing for TerraSAR-X using a new fomulation of the extended chirp scaling algorithm,” IGARSS2003, vol.3, p.1462-1464, 2003.を参照）。 Next, in step ST10 described above, the image reproduction unit 11 reproduces an image with respect to the first channel signal and the second channel signal to which the restoration algorithm unit 10 has performed the restoration algorithm. Examples of the image reproduction method include extended chirp scaling (for example, the above-mentioned non-patent documents J. Mittermayer, R. Lord, and E. B¨oner, “Sliding spotlight SAR processing for TerraSAR-X using a”. See new fomulation of the extended chirp scaling algorithm, ”IGARSS2003, vol.3, p.1462-1464, 2003.).
　次に、上述のステップＳＴ１１において、サブアパーチャー結合部１２は、画像再生部１１が画像再生を行った第１のチャネル信号及び第２のチャネル信号に対してサブアパーチャー結合を行うことによりＳＡＲ画像を生成する。 Next, in step ST11 described above, the sub-aperture coupling unit 12 obtains a SAR image by performing sub-aperture coupling to the first channel signal and the second channel signal for which the image reproduction unit 11 has reproduced the image. Generate.
　当該具体例の構成によれば、スライディングスポットライト観測によってアジマスアンビギュイティが多重化する場合にも，マルチチャネルＳＡＲにおけるチャネル信号間のインバランスを補正することが可能である。当該具体例では，マルチチャネルＳＡＲによる観測をスライディングスポットライト観測としたが、マルチチャネルＳＡＲがフルスポットライト観測を行う場合にも適用可能である。なお、本具体例では、２回のバンドパスフィルタによる帯域制限の後段で、インバランス補正部６が位相インバランスの補正のみを行ったが、インバランス補正部６は、レンジサンプルずれの補正等のその他のインバランスの補正を行ってもよい。また、ドップラー周波数領域帯域制限部３及びヒット領域帯域制限部５の各バンドパスフィルタによる２回の帯域制限を行ったが、ドップラー周波数領域帯域制限部３によるドップラー周波数領域の帯域制限は行わず、ヒット領域帯域制限部５によってヒット領域のみ帯域制限を行ってもよい。 According to the configuration of the specific example, it is possible to correct the imbalance between the channel signals in the multi-channel SAR even when the azimuth ambiguity is multiplexed by the sliding spotlight observation. In this specific example, the observation by the multi-channel SAR is defined as the sliding spotlight observation, but it can also be applied to the case where the multi-channel SAR performs the full spotlight observation. In this specific example, the imbalance correction unit 6 only corrects the phase imbalance in the subsequent stage of the band limitation by the bandpass filter twice, but the imbalance correction unit 6 corrects the range sample deviation and the like. Other imbalance corrections may be made. Further, although the band path filters of the Doppler frequency domain band limiting unit 3 and the hit region band limiting unit 5 performed the band limitation twice, the Doppler frequency domain band limiting unit 3 did not limit the band of the Doppler frequency region. The hit area band limiting unit 5 may limit the band only in the hit area.
　レーダ信号処理装置１００における、電力インバランス補正部１、高速フーリエ変換部２、ドップラー周波数領域帯域制限部３、逆高速フーリエ変換部４、ヒット領域帯域制限部５、インバランス補正部６のドップラー中心周波数推定部７及び位相インバランス補正部８、サブアパーチャー分割部９、復元アルゴリズム部１０、画像再生部１１並びにサブアパーチャー結合部１２の各機能は、処理回路により実現される。すなわち、レーダ信号処理装置１００は、図２に示した各ステップの処理を実行するための処理回路を備える。この処理回路は、専用のハードウェアであってもよいが、メモリに記憶されたプログラムを実行するＣＰＵ（Ｃｅｎｔｒａｌ　Ｐｒｏｃｅｓｓｉｎｇ　Ｕｎｉｔ）であってもよい。 Doppler center of power imbalance correction unit 1, fast Fourier transform unit 2, Doppler frequency domain band limiting unit 3, inverse fast Fourier transform unit 4, hit region band limiting unit 5, and imbalance correction unit 6 in the radar signal processing device 100. Each function of the frequency estimation unit 7, the phase imbalance correction unit 8, the sub-aperture division unit 9, the restoration algorithm unit 10, the image reproduction unit 11, and the sub-aperture coupling unit 12 is realized by a processing circuit. That is, the radar signal processing device 100 includes a processing circuit for executing the processing of each step shown in FIG. This processing circuit may be dedicated hardware, or may be a CPU (Central Processing Unit) that executes a program stored in the memory.
　図４Ａは、レーダ信号処理装置１００の機能を実現するハードウェア構成を示すブロック図である。図４Ｂは、レーダ信号処理装置１００の機能を実現するソフトウェアを実行するハードウェア構成を示すブロック図である。 FIG. 4A is a block diagram showing a hardware configuration that realizes the functions of the radar signal processing device 100. FIG. 4B is a block diagram showing a hardware configuration for executing software that realizes the functions of the radar signal processing device 100.
　上記処理回路が図４Ａに示す専用のハードウェアの処理回路２０である場合、処理回路２０は、例えば、単一回路、複合回路、プログラム化したプロセッサ、並列プログラム化したプロセッサ、ＡＳＩＣ（Ａｐｐｌｉｃａｔｉｏｎ　Ｓｐｅｃｉｆｉｃ　Ｉｎｔｅｇｒａｔｅｄ　Ｃｉｒｃｕｉｔ）、ＦＰＧＡ（Ｆｉｅｌｄ－Ｐｒｏｇｒａｍｍａｂｌｅ　Ｇａｔｅ　Ａｒｒａｙ）又はこれらを組み合わせたものが該当する。 When the processing circuit is the processing circuit 20 of the dedicated hardware shown in FIG. 4A, the processing circuit 20 may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, or an ASIC (Application Specific Integrated Circuitd). Circuit), FPGA (Field-Programmable Gate Array) or a combination thereof is applicable.
　レーダ信号処理装置１００における、電力インバランス補正部１、高速フーリエ変換部２、ドップラー周波数領域帯域制限部３、逆高速フーリエ変換部４、ヒット領域帯域制限部５、インバランス補正部６のドップラー中心周波数推定部７及び位相インバランス補正部８、サブアパーチャー分割部９、復元アルゴリズム部１０、画像再生部１１並びにサブアパーチャー結合部１２の各機能を別々の処理回路で実現してもよいし、これらの機能をまとめて１つの処理回路で実現してもよい。 Doppler center of power imbalance correction unit 1, fast Fourier transform unit 2, Doppler frequency domain band limiting unit 3, inverse fast Fourier transform unit 4, hit region band limiting unit 5, and imbalance correction unit 6 in the radar signal processing device 100. The functions of the frequency estimation unit 7, the phase imbalance correction unit 8, the sub-aperture division unit 9, the restoration algorithm unit 10, the image reproduction unit 11, and the sub-aperture coupling unit 12 may be realized by separate processing circuits, or these may be realized. The functions may be collectively realized by one processing circuit.
　上記処理回路が図４Ｂに示すプロセッサ２１である場合、レーダ信号処理装置１００における、電力インバランス補正部１、高速フーリエ変換部２、ドップラー周波数領域帯域制限部３、逆高速フーリエ変換部４、ヒット領域帯域制限部５、インバランス補正部６のドップラー中心周波数推定部７及び位相インバランス補正部８、サブアパーチャー分割部９、復元アルゴリズム部１０、画像再生部１１並びにサブアパーチャー結合部１２の各機能は、ソフトウェア、ファームウェア又はソフトウェアとファームウェアとの組み合わせによって実現される。
　なお、ソフトウェア又はファームウェアは、プログラムとして記述されてメモリ２２に記憶される。 When the processing circuit is the processor 21 shown in FIG. 4B, the power imbalance correction unit 1, the fast Fourier transform unit 2, the Doppler frequency domain band limiting unit 3, the inverse fast Fourier transform unit 4, and the hit in the radar signal processing device 100. Functions of the region band limiting unit 5, the Doppler center frequency estimation unit 7 of the imbalance correction unit 6, the phase imbalance correction unit 8, the sub-aperture division unit 9, the restoration algorithm unit 10, the image reproduction unit 11, and the sub-aperture coupling unit 12. Is realized by software, firmware or a combination of software and firmware.
The software or firmware is described as a program and stored in the memory 22.
　プロセッサ２１は、メモリ２２に記憶されたプログラムを読み出して実行することにより、レーダ信号処理装置１００における、電力インバランス補正部１、高速フーリエ変換部２、ドップラー周波数領域帯域制限部３、逆高速フーリエ変換部４、ヒット領域帯域制限部５、インバランス補正部６のドップラー中心周波数推定部７及び位相インバランス補正部８、サブアパーチャー分割部９、復元アルゴリズム部１０、画像再生部１１並びにサブアパーチャー結合部１２の各機能を実現する。すなわち、レーダ信号処理装置１００は、これらの各機能がプロセッサ２１によって実行されるときに、図２に示した各ステップの処理が結果的に実行されるプログラムを記憶するためのメモリ２２を備える。 By reading and executing the program stored in the memory 22, the processor 21 reads and executes the power imbalance correction unit 1, the fast Fourier transform unit 2, the Doppler frequency domain band limiting unit 3, and the inverse high-speed Fourier in the radar signal processing device 100. Conversion unit 4, hit region band limiting unit 5, Doppler center frequency estimation unit 7 and phase imbalance correction unit 8 of imbalance correction unit 6, sub-aperture division unit 9, restoration algorithm unit 10, image reproduction unit 11, and sub-aperture coupling. Each function of the part 12 is realized. That is, the radar signal processing device 100 includes a memory 22 for storing a program in which the processing of each step shown in FIG. 2 is executed as a result when each of these functions is executed by the processor 21.
　これらのプログラムは、レーダ信号処理装置１００における、電力インバランス補正部１、高速フーリエ変換部２、ドップラー周波数領域帯域制限部３、逆高速フーリエ変換部４、ヒット領域帯域制限部５、インバランス補正部６のドップラー中心周波数推定部７及び位相インバランス補正部８、サブアパーチャー分割部９、復元アルゴリズム部１０、画像再生部１１並びにサブアパーチャー結合部１２の各手順又は方法をコンピュータに実行させる。メモリ２２は、コンピュータを、レーダ信号処理装置１００における、電力インバランス補正部１、高速フーリエ変換部２、ドップラー周波数領域帯域制限部３、逆高速フーリエ変換部４、ヒット領域帯域制限部５、インバランス補正部６のドップラー中心周波数推定部７及び位相インバランス補正部８、サブアパーチャー分割部９、復元アルゴリズム部１０、画像再生部１１並びにサブアパーチャー結合部１２として機能させるためのプログラムが記憶されたコンピュータ可読記憶媒体であってもよい。 These programs include a power imbalance correction unit 1, a high-speed Fourier transform unit 2, a Doppler frequency domain band limiting unit 3, an inverse fast Fourier transform unit 4, a hit region band limiting unit 5, and an imbalance correction in the radar signal processing device 100. The computer is made to execute each procedure or method of the Doppler center frequency estimation unit 7 of the unit 6, the phase imbalance correction unit 8, the sub-aperture division unit 9, the restoration algorithm unit 10, the image reproduction unit 11, and the sub-aperture coupling unit 12. The memory 22 uses the computer as a power imbalance correction unit 1, a fast Fourier transform unit 2, a Doppler frequency domain band limiting unit 3, an inverse fast Fourier transform unit 4, a hit region band limiting unit 5, and an algorithm in the radar signal processing device 100. A program for functioning as the Doppler center frequency estimation unit 7 of the balance correction unit 6, the phase imbalance correction unit 8, the sub-aperture division unit 9, the restoration algorithm unit 10, the image reproduction unit 11, and the sub-aperture coupling unit 12 is stored. It may be a computer-readable storage medium.
　プロセッサ２１には、例えば、ＣＰＵ（Ｃｅｎｔｒａｌ　Ｐｒｏｃｅｓｓｉｎｇ　Ｕｎｉｔ）、処理装置、演算装置、プロセッサ、マイクロプロセッサ、マイクロコンピュータ、またはＤＳＰ（Ｄｉｇｉｔａｌ　Ｓｉｇｎａｌ　Ｐｒｏｃｅｓｓｏｒ）などが該当する。 The processor 21 corresponds to, for example, a CPU (Central Processing Unit), a processing device, a computing device, a processor, a microprocessor, a microcomputer, a DSP (Digital Signal Processor), or the like.
　メモリ２２には、例えば、ＲＡＭ（Ｒａｎｄｏｍ　Ａｃｃｅｓｓ　Ｍｅｍｏｒｙ）、ＲＯＭ（Ｒｅａｄ　Ｏｎｌｙ　Ｍｅｍｏｒｙ）、フラッシュメモリ、ＥＰＲＯＭ（Ｅｒａｓａｂｌｅ　Ｐｒｏｇｒａｍｍａｂｌｅ　Ｒｅａｄ　Ｏｎｌｙ　Ｍｅｍｏｒｙ）、ＥＥＰＲＯＭ（Ｅｌｅｃｔｒｉｃａｌｌｙ－ＥＰＲＯＭ）などの不揮発性又は揮発性の半導体メモリ、ハードディスク、フレキシブルディスク等の磁気ディスク、フレキシブルディスク、光ディスク、コンパクトディスク、ミニディスク、ＣＤ（Ｃｏｍｐａｃｔ　Ｄｉｓｃ）、ＤＶＤ（Ｄｉｇｉｔａｌ　Ｖｅｒｓａｔｉｌｅ　Ｄｉｓｃ）などが該当する。 The memory 22 may include, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), an EPROM (Electrically-volatile) semiconductor, or an EPROM (Electrically-EPROM). This includes hard disks, magnetic disks such as flexible disks, flexible disks, optical discs, compact disks, mini disks, CDs (Compact Disc), DVDs (Digital Versailles Disc), and the like.
　レーダ信号処理装置１００における、電力インバランス補正部１、高速フーリエ変換部２、ドップラー周波数領域帯域制限部３、逆高速フーリエ変換部４、ヒット領域帯域制限部５、インバランス補正部６のドップラー中心周波数推定部７及び位相インバランス補正部８、サブアパーチャー分割部９、復元アルゴリズム部１０、画像再生部１１並びにサブアパーチャー結合部１２の各機能について一部を専用のハードウェアで実現し、一部をソフトウェア又はファームウェアで実現してもよい。 Doppler center of power imbalance correction unit 1, fast Fourier transform unit 2, Doppler frequency domain band limiting unit 3, inverse fast Fourier transform unit 4, hit region band limiting unit 5, and imbalance correction unit 6 in the radar signal processing device 100. Some of the functions of the frequency estimation unit 7, the phase imbalance correction unit 8, the sub-aperture division unit 9, the restoration algorithm unit 10, the image reproduction unit 11, and the sub-aperture coupling unit 12 are realized by dedicated hardware, and some of them are realized. May be realized by software or firmware.
　例えば、電力インバランス補正部１、高速フーリエ変換部２、ドップラー周波数領域帯域制限部３、逆高速フーリエ変換部４及びヒット領域帯域制限部５の各機能は、専用のハードウェアとしての処理回路で機能を実現する。インバランス補正部６のドップラー中心周波数推定部７及び位相インバランス補正部８、サブアパーチャー分割部９、復元アルゴリズム部１０、画像再生部１１並びにサブアパーチャー結合部１２については、プロセッサ２１がメモリ２２に記憶されたプログラムを読み出して実行することにより機能を実現してもよい。
　このように、処理回路は、ハードウェア、ソフトウェア、ファームウェア又はこれらの組み合わせにより上記機能のそれぞれを実現することができる。 For example, each function of the power imbalance correction unit 1, the fast Fourier transform unit 2, the Doppler frequency domain band limiting unit 3, the inverse fast Fourier transform unit 4, and the hit region band limiting unit 5 is a processing circuit as dedicated hardware. Realize the function. For the Doppler center frequency estimation unit 7 and phase imbalance correction unit 8, sub-aperture division unit 9, restoration algorithm unit 10, image reproduction unit 11, and sub-aperture coupling unit 12 of the imbalance correction unit 6, the processor 21 is stored in the memory 22. The function may be realized by reading and executing the stored program.
As described above, the processing circuit can realize each of the above functions by hardware, software, firmware or a combination thereof.
　以上のように、実施の形態１に係るレーダ信号処理装置１００は、マルチチャネルＳＡＲによる観測によって得られた複数のチャネル信号に対して、それぞれ、ヒット領域における帯域制限を行うヒット領域帯域制限部５と、ヒット領域帯域制限部５がヒット領域における帯域制限を行った複数のチャネル信号に基づいて、チャネル信号間のインバランス補正を行うインバランス補正部６と、を備えている。 As described above, the radar signal processing device 100 according to the first embodiment has the hit area band limiting unit 5 that limits the band in the hit area for each of the plurality of channel signals obtained by the observation by the multi-channel SAR. And an imbalance correction unit 6 that performs imbalance correction between channel signals based on a plurality of channel signals for which the hit region band limiting unit 5 has band-limited in the hit region.
　上記の構成によれば、ヒット領域における帯域制限によりアジマスアンビギュイティが分離された信号が得られる。これにより得られた信号に対してインバランス補正を行うことによって、チャネル信号間のインバランス補正の精度を向上させることができる。 According to the above configuration, a signal in which the azimuth ambiguity is separated can be obtained due to the band limitation in the hit region. By performing imbalance correction on the signal obtained thereby, the accuracy of imbalance correction between channel signals can be improved.
　実施の形態１に係るレーダ信号処理装置１００におけるヒット領域帯域制限部５は、ヒット領域における帯域制限によって、ヒット中心を中心とした帯域のチャネル信号を抽出する。
　上記の構成によれば、ヒット中心を中心とした帯域のチャネル信号を抽出する帯域制限によりアジマスアンビギュイティが分離された信号が得られる。これにより得られた信号に対してインバランス補正を行うことによって、チャネル信号間のインバランス補正の精度を向上させることができる。 The hit region band limiting unit 5 in the radar signal processing device 100 according to the first embodiment extracts a channel signal in a band centered on the hit center by band limiting in the hit region.
According to the above configuration, a signal in which the azimuth ambiguity is separated can be obtained by band limitation for extracting the channel signal in the band centered on the hit center. By performing imbalance correction on the signal obtained thereby, the accuracy of imbalance correction between channel signals can be improved.
　実施の形態１に係るレーダ信号処理装置１００は、複数のチャネル信号に対して、それぞれ、ドップラー周波数変換を行う高速フーリエ変換部２と、高速フーリエ変換部２がドップラー周波数変換を行った複数のチャネル信号に対して、それぞれ、ドップラー周波数領域における帯域制限を行うドップラー周波数領域帯域制限部３と、ドップラー周波数領域帯域制限部３がドップラー周波数領域における帯域制限を行った複数のチャネル信号に対して、それぞれ、逆ドップラー周波数変換を行う逆高速フーリエ変換部４と、をさらに備え、ヒット領域帯域制限部５は、逆高速フーリエ変換部４が逆ドップラー周波数変換を行った複数のチャネル信号に対して、それぞれ、ヒット領域における帯域制限を行う。 The radar signal processing device 100 according to the first embodiment has a high-speed Fourier conversion unit 2 that performs Doppler frequency conversion on a plurality of channel signals, and a plurality of channels that the high-speed Fourier conversion unit 2 performs Doppler frequency conversion. For each of the signals, the Doppler frequency domain band limiting unit 3 that limits the band in the Doppler frequency domain and the plurality of channel signals that the Doppler frequency domain band limiting section 3 band limits in the Doppler frequency domain, respectively. , Inverse high-speed Fourier conversion unit 4 that performs inverse Doppler frequency conversion, and the hit region band limiting unit 5 for each of a plurality of channel signals that the inverse high-speed Fourier conversion unit 4 has performed inverse Doppler frequency conversion. , Band limitation in the hit area.
　上記の構成によれば、ヒット領域における帯域制限、及びドップラー周波数領域における帯域制限によりアジマスアンビギュイティが分離された信号が得られる。これにより得られた信号に対してインバランス補正を行うことによって、チャネル信号間のインバランス補正の精度を向上させることができる。 According to the above configuration, a signal in which the azimuth ambiguity is separated can be obtained due to the band limitation in the hit region and the band limitation in the Doppler frequency region. By performing imbalance correction on the signal obtained thereby, the accuracy of imbalance correction between channel signals can be improved.
　実施の形態１に係るレーダ信号処理装置１００におけるドップラー周波数領域帯域制限部３は、ドップラー周波数領域における帯域制限によって、ドップラー中心周波数を中心とした帯域のチャネル信号を抽出する。 The Doppler frequency domain band limiting unit 3 in the radar signal processing device 100 according to the first embodiment extracts a channel signal in a band centered on the Doppler center frequency by band limiting in the Doppler frequency domain.
　上記の構成によれば、ドップラー中心周波数を中心とした帯域のチャネル信号を抽出する帯域制限によりアジマスアンビギュイティが分離された信号が得られる。これにより得られた信号に対してインバランス補正を行うことによって、チャネル信号間のインバランス補正の精度を向上させることができる。 According to the above configuration, a signal in which the azimuth ambiguity is separated can be obtained by band limitation for extracting the channel signal in the band centered on the Doppler center frequency. By performing imbalance correction on the signal obtained thereby, the accuracy of imbalance correction between channel signals can be improved.
　実施の形態１に係るレーダ信号処理装置１００におけるインバランス補正部６は、インバランス補正として、位相インバランスの補正を行う。
　上記の構成によれば、帯域制限によりアジマスアンビギュイティが分離された信号に対して位相インバランス補正を行うことによって、チャネル信号間の位相インバランス補正の精度を向上させることができる。 The imbalance correction unit 6 in the radar signal processing device 100 according to the first embodiment corrects the phase imbalance as the imbalance correction.
According to the above configuration, the accuracy of the phase imbalance correction between the channel signals can be improved by performing the phase imbalance correction on the signal whose azimuth ambiguity is separated by the band limitation.
　実施の形態１に係るレーダ信号処理装置１００におけるインバランス補正部６は、インバランス補正として、レンジサンプルずれの補正を行ってもよい。
　上記の構成によれば、帯域制限によりアジマスアンビギュイティが分離された信号に対してレンジサンプルずれの補正を行うことによって、チャネル信号間のレンジサンプルずれの補正精度を向上させることができる。 The imbalance correction unit 6 in the radar signal processing device 100 according to the first embodiment may correct the range sample deviation as the imbalance correction.
According to the above configuration, it is possible to improve the correction accuracy of the range sample deviation between the channel signals by correcting the range sample deviation for the signal whose azimuth ambiguity is separated by the band limitation.
　実施の形態１に係るレーダ信号処理装置１００におけるマルチチャネルＳＡＲによる観測は、スライディングスポット観測、又はフルスポットライト観測である。
　上記の構成によれば、スライディングスポット観測、又はフルスポットライト観測によってアジマスアンビギュイティが多重化した場合に、チャネル信号間のインバランス補正の精度を向上させることができる。 The observation by the multi-channel SAR in the radar signal processing apparatus 100 according to the first embodiment is a sliding spot observation or a full spotlight observation.
According to the above configuration, when the azimuth ambiguity is multiplexed by sliding spot observation or full spotlight observation, the accuracy of imbalance correction between channel signals can be improved.
　実施の形態１に係るレーダ信号処理方法は、マルチチャネルＳＡＲによる観測によって得られた複数のチャネル信号に対して、それぞれ、ヒット領域における帯域制限を行うヒット領域帯域制限ステップと、ヒット領域帯域制限ステップでヒット領域における帯域制限を行った複数のチャネル信号に基づいて、チャネル信号間のインバランス補正を行うインバランス補正ステップと、を含む。
　上記の構成によれば、実施の形態１に係るレーダ信号処理装置１００が奏する効果と同様の効果を奏する。
　なお、実施の形態の任意の構成要素の変形、もしくは実施の形態の任意の構成要素の省略が可能である。 In the radar signal processing method according to the first embodiment, a hit area band limiting step and a hit area band limiting step for band limiting in the hit region are performed for a plurality of channel signals obtained by observation by the multi-channel SAR, respectively. Includes an imbalance correction step of performing imbalance correction between channel signals based on a plurality of channel signals for which band limitation has been performed in the hit region.
According to the above configuration, the same effect as that of the radar signal processing device 100 according to the first embodiment is obtained.
It is possible to modify any component of the embodiment or omit any component of the embodiment.
　本開示に係るレーダ処理装置は、チャネル信号間のインバランス補正の精度を向上させることができるため、マルチチャネルＳＡＲの技術に利用可能である。 The radar processing device according to the present disclosure can be used in the multi-channel SAR technique because it can improve the accuracy of imbalance correction between channel signals.
　１　電力インバランス補正部、２　高速フーリエ変換部、３　ドップラー周波数領域帯域制限部、４　逆高速フーリエ変換部、５　ヒット領域帯域制限部、６　インバランス補正部、７　ドップラー中心周波数推定部、８　位相インバランス補正部、９　サブアパーチャー分割部、１０　復元アルゴリズム部、１１　画像再生部、１２　サブアパーチャー結合部、２０　処理回路、２１　プロセッサ、２２　メモリ、１００　レーダ信号処理装置。 1 power imbalance correction unit, 2 high-speed Fourier transform unit, 3 Doppler frequency domain band limiting unit, 4 inverse fast Fourier transform unit, 5 hit region band limiting unit, 6 imbalance correction unit, 7 Doppler center frequency estimation unit, 8 phase Imbalance correction unit, 9 sub-aperture division unit, 10 restoration algorithm unit, 11 image reproduction unit, 12 sub-aperture coupling unit, 20 processing circuit, 21 processor, 22 memory, 100 radar signal processing device.

Claims (8)

  1. 　マルチチャネルＳＡＲによる観測によって得られた複数のチャネル信号に対して、それぞれ、ヒット領域における帯域制限を行うヒット領域帯域制限部と、
    　前記ヒット領域帯域制限部が前記ヒット領域における帯域制限を行った複数のチャネル信号に基づいて、チャネル信号間のインバランス補正を行うインバランス補正部と、を備えていることを特徴とする、レーダ信号処理装置。     A hit area band limiting unit that limits the band in the hit area for a plurality of channel signals obtained by observation by the multi-channel SAR, respectively.
    The radar is characterized in that the hit region band limiting unit includes an imbalance correction unit that performs imbalance correction between channel signals based on a plurality of channel signals for which band limitation is performed in the hit region. Signal processing device.
  2. 　前記ヒット領域帯域制限部は、前記ヒット領域における帯域制限によって、ヒット中心を中心とした帯域のチャネル信号を抽出することを特徴とする、請求項１に記載のレーダ信号処理装置。 The radar signal processing device according to claim 1, wherein the hit region band limiting unit extracts a channel signal in a band centered on the hit center by band limiting in the hit region.
  3. 　前記複数のチャネル信号に対して、それぞれ、ドップラー周波数変換を行う高速フーリエ変換部と、
    　前記高速フーリエ変換部が前記ドップラー周波数変換を行った複数のチャネル信号に対して、それぞれ、ドップラー周波数領域における帯域制限を行うドップラー周波数領域帯域制限部と、
    　前記ドップラー周波数領域帯域制限部が前記ドップラー周波数領域における帯域制限を行った複数のチャネル信号に対して、それぞれ、逆ドップラー周波数変換を行う逆高速フーリエ変換部と、をさらに備え、
    　前記ヒット領域帯域制限部は、前記逆高速フーリエ変換部が前記逆ドップラー周波数変換を行った複数のチャネル信号に対して、それぞれ、前記ヒット領域における帯域制限を行うことを特徴とする、請求項１に記載のレーダ信号処理装置。     A fast Fourier transform unit that performs Doppler frequency conversion for each of the plurality of channel signals,
    A Doppler frequency domain band limiting section that limits the band in the Doppler frequency domain for a plurality of channel signals that have undergone the Doppler frequency transform by the fast Fourier transform section, respectively.
    The Doppler frequency domain band limiting section further includes an inverse fast Fourier transform section that performs inverse Doppler frequency conversion for each of a plurality of channel signals for which band limiting has been performed in the Doppler frequency domain.
    The hit region band limiting unit is characterized in that the inverse fast Fourier transform unit performs band limitation in the hit region for each of a plurality of channel signals subjected to the inverse Doppler frequency conversion. The radar signal processing device described in.
  4. 　前記ドップラー周波数領域帯域制限部は、前記ドップラー周波数領域における帯域制限によって、ドップラー中心周波数を中心とした帯域のチャネル信号を抽出することを特徴とする、請求項３に記載のレーダ信号処理装置。 The radar signal processing device according to claim 3, wherein the Doppler frequency domain band limiting unit extracts a channel signal in a band centered on the Doppler center frequency by band limiting in the Doppler frequency domain.
  5. 　前記インバランス補正部は、前記インバランス補正として、位相インバランスの補正を行うことを特徴とする、請求項１に記載のレーダ信号処理装置。 The radar signal processing device according to claim 1, wherein the imbalance correction unit corrects a phase imbalance as the imbalance correction.
  6. 　前記インバランス補正部は、前記インバランス補正として、レンジサンプルずれの補正を行うことを特徴とする、請求項１に記載のレーダ信号処理装置。 The radar signal processing device according to claim 1, wherein the imbalance correction unit corrects a range sample deviation as the imbalance correction.
  7. 　前記観測は、スライディングスポット観測、又はフルスポットライト観測であることを特徴とする、請求項１に記載のレーダ信号処理装置。 The radar signal processing device according to claim 1, wherein the observation is a sliding spot observation or a full spotlight observation.
  8. 　マルチチャネルＳＡＲによる観測によって得られた複数のチャネル信号に対して、それぞれ、ヒット領域における帯域制限を行うヒット領域帯域制限ステップと、
    　前記ヒット領域帯域制限ステップで前記ヒット領域における帯域制限を行った複数のチャネル信号に基づいて、チャネル信号間のインバランス補正を行うインバランス補正ステップと、を含むことを特徴とする、レーダ信号処理方法。     A hit region bandwidth limiting step that limits the bandwidth in the hit region for a plurality of channel signals obtained by observation by the multi-channel SAR, respectively.
    Radar signal processing comprising an imbalance correction step of performing imbalance correction between channel signals based on a plurality of channel signals for which band limitation is performed in the hit region in the hit area band limiting step. Method.
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