CN112859122A - Multi-subband signal error estimation and compensation method for high-resolution spaceborne SAR system - Google Patents

Multi-subband signal error estimation and compensation method for high-resolution spaceborne SAR system Download PDF

Info

Publication number
CN112859122A
CN112859122A CN202110031851.2A CN202110031851A CN112859122A CN 112859122 A CN112859122 A CN 112859122A CN 202110031851 A CN202110031851 A CN 202110031851A CN 112859122 A CN112859122 A CN 112859122A
Authority
CN
China
Prior art keywords
sub
band
error
strong point
amplitude
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
CN202110031851.2A
Other languages
Chinese (zh)
Other versions
CN112859122B (en
Inventor
匡辉
张庆君
张润宁
刘杰
程晓
于海锋
王志斌
刘磊
杜剑波
刘书豪
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Beijing Institute of Spacecraft System Engineering
Original Assignee
Beijing Institute of Spacecraft System Engineering
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Beijing Institute of Spacecraft System Engineering filed Critical Beijing Institute of Spacecraft System Engineering
Priority to CN202110031851.2A priority Critical patent/CN112859122B/en
Publication of CN112859122A publication Critical patent/CN112859122A/en
Application granted granted Critical
Publication of CN112859122B publication Critical patent/CN112859122B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • 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
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/35—Constructional details or hardware or software details of the signal processing chain
    • G01S19/37—Hardware or software details of the signal processing chain

Abstract

The invention relates to a multi-subband signal error estimation and compensation method for a high-resolution spaceborne SAR system, belonging to the field of signal processing; step one, calculating the amplitude error A 'of the signal in each sub-band by adopting a phase gradient self-focusing method based on the strong point target in the imaging data of each sub-band'k(fτ) And phase error of phi'k(fτ) (ii) a Step two, calculating the amplitude error delta Pp of the signals between the sub-bandskPhase error Δ αkAnd delay error Δ tk(ii) a Performing error compensation on multi-sub-band imaging data of the original data, and performing multi-sub-band signal splicing to obtain a full-resolution SAR image, thereby realizing the improvement of the range-to-resolution; the invention estimates the amplitude and phase error of each sub-band signal by adopting a phase gradient self-focusing method based on the imaging data of each sub-band, further estimates the time delay, amplitude and phase error among the sub-bands on the basis, and provides an error compensation method in the sub-bands and among the sub-bands.

Description

Multi-subband signal error estimation and compensation method for high-resolution spaceborne SAR system
Technical Field
The invention belongs to the field of signal processing, and relates to a multi-subband signal error estimation and compensation method for a high-resolution spaceborne SAR system.
Background
The resolution is a core index of the satellite-borne SAR system, the higher the resolution is, the stronger the ability of the system to accurately describe a target is, which is beneficial to extracting target characteristics, and the high-resolution satellite-borne SAR system is vigorously developed in all countries in the world at present. The space-borne SAR mainly realizes distance direction high-resolution imaging by transmitting a large-bandwidth linear frequency modulation signal, but the bandwidth of a transmitting signal is improved along with the continuous improvement of the resolution, and for a high-resolution space-borne SAR system, for example, in order to realize the resolution of 0.15m, the bandwidth of the transmitting signal required by the high-resolution space-borne SAR system exceeds 2 GHz. The transmission and reception of such signals with large bandwidth face many technical and methodological difficulties, and a common solution is to transmit several sub-band signals with different carrier frequencies, and then splice and synthesize the sub-band signals by a digital signal processing method, so as to obtain a signal with large bandwidth and obtain a distance-direction high-resolution image.
However, two preconditions are needed for synthesizing high-quality large-bandwidth signals by adopting multiple sub-bands, firstly, the amplitude and phase errors in each sub-band are small, and the compression quality of the sub-band signals is not influenced; secondly, each subband has better time delay, amplitude and phase consistency. However, for a multi-subband large-bandwidth satellite-borne SAR system, different subband signals pass through different hardware systems such as a transmitting channel and a receiving channel, and meanwhile, transmission characteristics of the different subband signals in atmospheric propagation are different, which not only causes amplitude and phase errors in subbands, but also causes time delay, amplitude and phase inconsistency errors among the subbands, and errors in the subbands and among the subbands affect the signal quality after multi-subband synthesis, thereby affecting the imaging quality. The intra-subband and inter-subband errors of the SAR system can be extracted to a certain extent through the internal calibration signal, but the link of the internal calibration signal is not identical to that of the actual imaging signal, and the errors caused by factors such as atmospheric propagation and the like are not considered.
Disclosure of Invention
The technical problem solved by the invention is as follows: the method comprises the steps of estimating the amplitude and phase errors of sub-band signals by adopting a phase gradient self-focusing method based on the imaging data of each sub-band, further estimating the time delay, amplitude and phase errors among the sub-bands on the basis, and providing an error compensation method in the sub-bands and among the sub-bands.
The technical scheme of the invention is as follows:
a multi-subband signal error estimation and compensation method for a high-resolution spaceborne SAR system comprises the following steps:
step one, calculating the amplitude error A 'of the signal in each sub-band by adopting a phase gradient self-focusing method based on the strong point target in the imaging data of each sub-band'k(fτ) And phase error of phi'k(fτ)；
Step two, calculating the amplitude error delta Pp of the signals between the sub-bandskPhase error Δ αkAnd delay error Δ tk；
Step three, according to the amplitude error A 'of the signals in the sub-band'k(fτ) Phase error of phi'k(fτ) And the amplitude error Δ Ρ of the inter-subband signalkPhase error Δ αkAnd delay error Δ tkAnd carrying out error compensation on the multi-sub-band imaging data of the original data, and splicing multi-sub-band signals to obtain a full-resolution SAR image so as to realize the improvement of the range-to-resolution.
In the method for estimating and compensating the error of the multi-subband signal of the high-resolution spaceborne SAR system, in the first step, the error is countedCalculating the signal amplitude error A 'in each sub-band'k(fτ) And phase error of phi'k(fτ) The specific method comprises the following steps:
s11, judging whether strong point targets exist or not line by line according to the sub-band imaging data, selecting data with the lines where the strong point targets exist, adding a rectangular window by taking the position where the strong point targets exist as the center, and setting pixel units outside the rectangular window to be zero; marking as strong point target data in the rectangular window;
s12, performing time domain interpolation processing on each strong point target data;
s13, searching peak position line by line for the strong point target data after time domain interpolation processing, and recording the time delay of the nth strong point target data of the kth sub-band as tk,n；
S14, adding a rectangular window again by taking the strong point target after each sub-band time domain interpolation processing as the center, and setting the pixel unit outside the rectangular window to be zero; carrying out amplitude normalization processing on data in the rectangular window, and converting the data into a distance frequency domain through distance-to-FFT conversion;
s15, calculating a primary compensation filter function H1,k(fτN); the data of each line of each sub-band is matched with a primary compensation filter function H1,k(fτN) multiplying to realize the compensation of the primary phase and the constant delay phase of each strong point target;
s16, amplitude normalization processing is carried out on the sub-band distances along the line of the frequency domain data, and the amplitude error A 'in each sub-band is calculated'k(fτ)；
S17, calculating the phase gradient of each sub-band
Figure BDA0002892675040000032
For phase gradient
Figure BDA0002892675040000033
Integral phase phi obtained by integrationk(fτ) Will integrate the phase phik(fτ) Phase phi of zero frequency subtractionk(0) To obtain the phase error phi 'in the sub-band'k(fτ)。
In one of the aboveA multi-subband signal error estimation and compensation method for a high-resolution satellite-borne SAR system is disclosed, wherein in S15, a primary compensation filter function H1,k(fτAnd n) the calculation method comprises the following steps:
H1,k(fτ,n)＝exp{j2π(fτ+fc,k)tk,n}
in the formula (f)τIs a distance frequency point;
fc,kthe central frequency point of the kth sub-band;
tk,nthe time delay of the nth strong point target data of the kth sub-band.
In the method for estimating and compensating the error of the multi-subband signal of the high-resolution spaceborne SAR system, in S16, the amplitude error a 'in each subband'k(fτ) The calculation method comprises the following steps:
Figure BDA0002892675040000031
in the formula, Ak(n,fτ) For the nth row frequency f of the kth sub-bandτProcessing the amplitude value;
n is the number of rows of each sub-band data and is also equal to the number of selected strong point targets;
fτis a distance frequency point;
b is the subband signal bandwidth.
In the method for estimating and compensating the multi-subband signal error of the high-resolution spaceborne SAR system, in step S17, the phase gradient is used
Figure BDA0002892675040000041
The calculation method comprises the following steps:
Figure BDA0002892675040000042
in the formula, Sk(n,fτ) For the nth row frequency f of the kth sub-bandτA frequency domain signal function of the amplitude values;
S* k(n,fτ) Is Sk(n,fτ) The conjugate function of (a).
In the aforementioned method for estimating and compensating the multi-subband signal error of the high-resolution spaceborne SAR system, in the second step, the amplitude error Δ Ρ of the inter-subband signalkPhase error Δ αkAnd delay error Δ tkThe calculation method comprises the following steps:
s21, judging whether strong point targets exist or not line by line according to the sub-band imaging data, selecting data with the lines where the strong point targets exist, adding a rectangular window by taking the position where the strong point targets exist as the center, and setting pixel units outside the rectangular window to be zero; marking as strong point target data in the rectangular window;
s22, performing distance direction FFT on the strong point target data of each sub-band, and transforming the strong point target data into a distance frequency domain;
s23, calculating a quadratic compensation filter function H2,k(fτ) Respectively connecting the strong point target data of each sub-band with a secondary compensation filter function H2,k(fτ) Multiplying to realize amplitude and phase error compensation in the sub-band;
s24, transforming the compensated strong point target data to a distance time domain through IFFT;
s25, the strong point target data after interpolation of each sub-band is subjected to line-by-line judgment of peak value positions; obtaining the time delay t 'of the nth strong point target of the kth sub-band through the imaging parameters'k,n(ii) a Calculating the time delay error delta t of the kth sub-band relative to the 1 st sub-bandk：
Figure BDA0002892675040000043
S26, extracting the phase of each line peak position of the interpolated strong point target data of each sub-band, and obtaining the phase of the nth strong point target of the kth sub-band as alpha through the imaging parametersk,nCalculating the phase error Delta alpha of the kth sub-band relative to the 1 st sub-bandkComprises the following steps:
Figure BDA0002892675040000044
fc,kthe central frequency point of the kth sub-band; f. ofc,1In the 1 st sub-bandA frequency point;
s27, extracting the amplitude of each line peak position of the interpolated strong point target data of each sub-band, and obtaining the amplitude of the nth strong point target of the kth sub-band as P through the imaging parametersk,n(ii) a Computing the amplitude error Δ Ρ of the kth subband with respect to the 1 st subbandk：
Figure BDA0002892675040000051
Ρ1,nThe amplitude of the nth strong point target of the 1 st sub-band.
In the method for estimating and compensating the multi-subband signal error of the high-resolution spaceborne SAR system, in S23, the secondary compensation filter function H2,k(fτ) The calculation method comprises the following steps:
H2,k(fτ)＝A′k(fτ)exp{-jΦ'k(fτ)}
of formula (II) to'k(fτ) The amplitude error in each sub-band;
Φ'k(fτ) Is the phase error within each subband.
In the method for estimating and compensating the error of the multi-subband signal of the high-resolution spaceborne SAR system, in the third step, error compensation is performed on the multi-subband imaging data of the original data, and the specific method for splicing the multi-subband signal comprises the following steps:
s31, transforming the original sub-band imaging data to a distance frequency domain through distance-direction FFT processing;
s32, in distance frequency domain, each sub-band signal and the quadratic compensation filter function H2,k(fτ) Multiplying to realize amplitude and phase error compensation in the sub-band;
s33, calculating a cubic compensation filter function H3,k(fτ)：
Figure BDA0002892675040000052
Each sub-band signal is combined with a cubic compensation filter function H3,k(fτ) Multiply by excelCompensating amplitude, phase and time delay errors among sub-bands;
s34, expanding the distance frequency domain to be larger than the total bandwidth of the multi-sub-band signal, and cutting and moving the effective distance frequency spectrum of each sub-band to the expanded distance frequency domain, wherein the frequency spectrum amount delta f of the k sub-band to be movedc,kComprises the following steps:
Δfc,k＝fc,k-fc
and S35, transforming the synthesized distance frequency domain signal into a distance time domain through distance to IFFT, and obtaining the full-resolution SAR image.
Compared with the prior art, the invention has the beneficial effects that:
(1) the method can realize the estimation of the amplitude and phase errors in each sub-band based on the strong point target in the imaging data of each sub-band and based on the phase gradient self-focusing method;
(2) the invention can further estimate the time delay, amplitude and phase error among the sub-bands, and provides a compensation method for the error in the sub-band and among the sub-bands, thereby completing the synthesis of multi-sub-band signals and obtaining a full-resolution SAR image;
(3) compared with the traditional intra-calibration data-based intra-subband and inter-subband errors of the SAR system, the method can estimate and compensate the intra-subband and inter-subband errors caused by atmospheric transmission and the like, has higher error estimation and compensation precision, can be simultaneously used for processing the calibration signals and the imaging signals in the high-resolution satellite-borne SAR multi-subband, and has better practical engineering application value.
Drawings
FIG. 1 is a flow chart of error estimation and compensation of multi-subband signals according to the present invention.
FIG. 2 shows (a) amplitude errors in subbands extracted by the present invention; (b) a phase error;
FIG. 3 shows the compression results of multiple subband signals before and after the error compensation in and between subbands: (a) the error between sub-bands is not compensated; (b) the error compensation in sub-band, the error between sub-bands is not compensated; (c) the error in the sub-band is not compensated, and the error between the sub-bands is compensated; (d) both the intra-subband and the inter-subband errors are compensated.
Detailed Description
The invention is further illustrated by the following examples.
The invention provides a multi-subband signal error estimation and compensation method for a high-resolution satellite-borne SAR system, which is characterized in that amplitude and phase errors of subband signals are estimated by adopting a phase gradient self-focusing method based on imaging data of each subband, and on the basis, time delay, amplitude and phase errors among subbands are further estimated, and an intra-subband and inter-subband error compensation method is provided.
A multi-subband signal error estimation and compensation method for a high-resolution spaceborne SAR system is shown in figure 1 and specifically comprises the following steps:
step one, estimating signal amplitude and phase error in a sub-band; based on strong point targets in the sub-band imaging data, calculating the amplitude error A 'of the signal in each sub-band by adopting a phase gradient self-focusing method'k(fτ) And phase error of phi'k(fτ) (ii) a The judgment of the strong point is based on that the amplitude of a certain distance pixel unit is higher than a certain threshold of other distance pixel units in the same row, and the selection of the threshold can be adjusted according to specific data.
Calculating signal amplitude error A 'in each sub-band'k(fτ) And phase error of phi'k(fτ) The specific method comprises the following steps:
s11, judging whether strong point targets exist or not line by line according to the sub-band imaging data, selecting data with the lines where the strong point targets exist, adding a rectangular window by taking the position where the strong point targets exist as the center, and setting pixel units outside the rectangular window to be zero; marking as strong point target data in the rectangular window;
s12, performing time domain interpolation processing on each strong point target data;
s13, searching peak position line by line for the strong point target data after time domain interpolation processing, and recording the time delay of the nth strong point target data of the kth sub-band as tk,n；
S14, adding a rectangular window again by taking the strong point target after each sub-band time domain interpolation processing as the center, and setting the pixel unit outside the rectangular window to be zero; carrying out amplitude normalization processing on data in the rectangular window, and converting the data into a distance frequency domain through distance-to-FFT conversion;
s15, calculating a primary compensation filter function H1,k(fτN); the data of each line of each sub-band is matched with a primary compensation filter function H1,k(fτN) multiplying to realize the compensation of the primary phase and the constant delay phase of each strong point target; first order compensation filter function H1,k(fτAnd n) the calculation method comprises the following steps:
H1,k(fτ,n)＝exp{j2π(fτ+fc,k)tk,n}
in the formula (f)τIs a distance frequency point;
fc,kthe central frequency point of the kth sub-band;
tk,nthe time delay of the nth strong point target data of the kth sub-band.
S16, amplitude normalization processing is carried out on the sub-band distances along the line of the frequency domain data, and the amplitude error A 'in each sub-band is calculated'k(fτ) (ii) a Amplitude error A 'in each subband'k(fτ) The calculation method comprises the following steps:
Figure BDA0002892675040000081
in the formula, Ak(n,fτ) For the nth row frequency f of the kth sub-bandτProcessing the amplitude value;
n is the number of rows of each sub-band data and is also equal to the number of selected strong point targets;
fτis a distance frequency point;
b is the subband signal bandwidth.
S17, calculating the phase gradient of each sub-band
Figure BDA0002892675040000082
For phase gradient
Figure BDA0002892675040000083
Integral phase phi obtained by integrationk(fτ) Will integrate overPhase phik(fτ) Phase phi of zero frequency subtractionk(0) To obtain the phase error phi 'in the sub-band'k(fτ)。
Phase gradient
Figure BDA0002892675040000084
The calculation method comprises the following steps:
Figure BDA0002892675040000085
in the formula, Sk(n,fτ) For the nth row frequency f of the kth sub-bandτA frequency domain signal function of the amplitude values;
S* k(n,fτ) Is Sk(n,fτ) The conjugate function of (a).
Step two, calculating the amplitude error delta Pp of the signals between the sub-bandskPhase error Δ αkAnd delay error Δ tk(ii) a In order to accurately extract the time delay of each strong point target, time domain interpolation needs to be performed on the selected strong point target data. After the amplitude and phase errors in the sub-bands are finished for the strong point target of each sub-band, the amplitude, the phase and the time delay of the strong point target among different sub-bands are compared and analyzed, and the signal amplitude, the phase and the time delay errors among the sub-bands are extracted.
The sub-band strong point target data can be transformed to a distance frequency domain through distance-to-Fourier transform (FFF), zero padding is carried out on the distance frequency domain, and further transformed to a distance time domain through distance-to-inverse Fourier transform (IFFT), so that time domain interpolation is realized.
Amplitude error Δ Ρ of inter-subband signalkPhase error Δ αkAnd delay error Δ tkThe calculation method comprises the following steps:
s21, judging whether strong point targets exist or not line by line according to the sub-band imaging data, selecting data with the lines where the strong point targets exist, adding a rectangular window by taking the position where the strong point targets exist as the center, and setting pixel units outside the rectangular window to be zero; marking as strong point target data in the rectangular window;
s22, performing distance direction FFT on the strong point target data of each sub-band, and transforming the strong point target data into a distance frequency domain;
s23, calculating a quadratic compensation filter function H2,k(fτ) Respectively connecting the strong point target data of each sub-band with a secondary compensation filter function H2,k(fτ) Multiplying to realize amplitude and phase error compensation in the sub-band; quadratic compensation filter function H2,k(fτ) The calculation method comprises the following steps:
H2,k(fτ)＝A′k(fτ)exp{-jΦ'k(fτ)}
of formula (II) to'k(fτ) The amplitude error in each sub-band;
Φ'k(fτ) Is the phase error within each subband.
S24, transforming the compensated strong point target data to a distance time domain through IFFT;
s25, the strong point target data after interpolation of each sub-band is subjected to line-by-line judgment of peak value positions; obtaining the time delay t 'of the nth strong point target of the kth sub-band through the imaging parameters'k,n(ii) a Calculating the time delay error delta t of the kth sub-band relative to the 1 st sub-bandk：
Figure BDA0002892675040000091
S26, extracting the phase of each line peak position of the interpolated strong point target data of each sub-band, and obtaining the phase of the nth strong point target of the kth sub-band as alpha through the imaging parametersk,nCalculating the phase error Delta alpha of the kth sub-band relative to the 1 st sub-bandkComprises the following steps:
Figure BDA0002892675040000092
fc,kthe central frequency point of the kth sub-band; f. ofc,1The center frequency point of the 1 st sub-band;
s27, extracting the amplitude of each line peak position of the interpolated strong point target data of each sub-band, and obtaining the amplitude of the nth strong point target of the kth sub-band as P through the imaging parametersk,n(ii) a Computing the amplitude error Δ Ρ of the kth subband with respect to the 1 st subbandk：
Figure BDA0002892675040000093
Ρ1,nThe amplitude of the nth strong point target of the 1 st sub-band.
Step three, according to the amplitude error A 'of the signals in the sub-band'k(fτ) Phase error of phi'k(fτ) And the amplitude error Δ Ρ of the inter-subband signalkPhase error Δ αkAnd delay error Δ tkAnd carrying out error compensation on the multi-sub-band imaging data of the original data, and splicing multi-sub-band signals to obtain a full-resolution SAR image so as to realize the improvement of the range-to-resolution.
The specific method for performing error compensation on the multi-subband imaging data of the original data and performing multi-subband signal splicing comprises the following steps:
s31, transforming the original sub-band imaging data to a distance frequency domain through distance-direction FFT processing;
s32, in distance frequency domain, each sub-band signal and the quadratic compensation filter function H2,k(fτ) Multiplying to realize amplitude and phase error compensation in the sub-band;
s33, calculating a cubic compensation filter function H3,k(fτ)：
Figure BDA0002892675040000101
Each sub-band signal is combined with a cubic compensation filter function H3,k(fτ) Multiplying to realize amplitude, phase and time delay error compensation among the sub-bands;
s34, expanding the distance frequency domain to be larger than the total bandwidth of the multi-sub-band signal, and cutting and moving the effective distance frequency spectrum of each sub-band to the expanded distance frequency domain, wherein the frequency spectrum amount delta f of the k sub-band to be movedc,kComprises the following steps:
Δfc,k＝fc,k-fc
and S35, transforming the synthesized distance frequency domain signal into a distance time domain through distance to IFFT, and obtaining the full-resolution SAR image.
To verify the correctness of the above method, the following simulation experiment was performed. The simulation includes 3 sub-bands, the bandwidth of each sub-band is 800MHz, the central frequency points are respectively 8.9GHz, 9.6GHz and 10.3GHz, the amplitude error and the phase error in each sub-band are shown in table 1, wherein each error value is a peak-to-peak value in the effective bandwidth (800 MHz). Table 2 gives the delay, amplitude and phase error for each subband relative to subband 1. In the simulation, 10 strong point targets are arranged and randomly distributed in the distance direction, the amplitude is randomly distributed between 0dB and 20dB, and the random phase is increased.
TABLE 1 amplitude and phase errors in subbands
Figure BDA0002892675040000111
TABLE 2 inter-subband delay, amplitude and phase error
Sub-band Delay error Amplitude error Phase error
Sub-band
1 0ns 0dB 0°
Sub-band 2 0.6ns 0.4dB -30°
Sub-band 3 -0.25ns -0.3dB 15°
Fig. 2(a) and (b) show the amplitude error and phase error, respectively, in each subband extracted using the method of the present invention. FIG. 3 shows the results before and after the intra-subband and inter-subband error compensation, and it can be seen from FIG. 3(a) that the compressed waveform is disordered after splicing the multiple subbands without performing the intra-subband and inter-subband error compensation; only the intra-subband error is compensated, and the inter-subband error is not compensated, so that the multi-subband splicing compressed waveform is still poor, as shown in fig. 3 (b); only the inter-subband error is compensated, the intra-subband error is not compensated, and a certain error still exists in the multi-subband splicing compressed waveform, but the target can be compressed better, as shown in fig. 3 (c); after simultaneously compensating the errors in the sub-bands and between the sub-bands, the multi-sub-band spliced signal can be completely compressed, as shown in fig. 3 (d). Therefore, the method can effectively extract the amplitude, the phase error and the time delay, the amplitude and the phase error among the sub-bands, can complete the error compensation and realize the splicing and the compression of the multi-sub-band signals.
Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make variations and modifications of the present invention without departing from the spirit and scope of the present invention by using the methods and technical contents disclosed above.

Claims (8)

1. A multi-subband signal error estimation and compensation method for a high-resolution spaceborne SAR system is characterized by comprising the following steps: the method comprises the following steps:
step one, calculating the amplitude error A 'of the signal in each sub-band by adopting a phase gradient self-focusing method based on the strong point target in the imaging data of each sub-band'k(fτ) And phase error of phi'k(fτ)；
Step two, calculating the amplitude error delta Pp of the signals between the sub-bandskPhase error Δ αkAnd delay error Δ tk；
Step three, according to the amplitude error A 'of the signals in the sub-band'k(fτ) Phase error of phi'k(fτ) And the amplitude error Δ Ρ of the inter-subband signalkPhase error Δ αkAnd delay error Δ tkAnd carrying out error compensation on the multi-sub-band imaging data of the original data, and splicing multi-sub-band signals to obtain a full-resolution SAR image so as to realize the improvement of the range-to-resolution.
2. The method for estimating and compensating the multi-subband signal error of the high-resolution spaceborne SAR system according to claim 1, characterized in that: in the first step, the signal amplitude error A 'in each sub-band is calculated'k(fτ) And phase error of phi'k(fτ) The specific method comprises the following steps:
s11, judging whether strong point targets exist or not line by line according to the sub-band imaging data, selecting data with the lines where the strong point targets exist, adding a rectangular window by taking the position where the strong point targets exist as the center, and setting pixel units outside the rectangular window to be zero; marking as strong point target data in the rectangular window;
s12, performing time domain interpolation processing on each strong point target data;
s13, searching peak position line by line for the strong point target data after time domain interpolation processing, and recording the time delay of the nth strong point target data of the kth sub-band as tk,n；
S14, adding a rectangular window again by taking the strong point target after each sub-band time domain interpolation processing as the center, and setting the pixel unit outside the rectangular window to be zero; carrying out amplitude normalization processing on data in the rectangular window, and converting the data into a distance frequency domain through distance-to-FFT conversion;
s15, calculating a primary compensation filter function H1,k(fτN); the data of each line of each sub-band is matched with a primary compensation filter function H1,k(fτN) multiplying to realize the compensation of the primary phase and the constant delay phase of each strong point target;
s16, amplitude normalization processing is carried out on the sub-band distances along the line of the frequency domain data, and the amplitude error A 'in each sub-band is calculated'k(fτ)；
S17, calculating the phase gradient of each sub-band
Figure FDA0002892675030000023
For phase gradient
Figure FDA0002892675030000024
Integral phase phi obtained by integrationk(fτ) Will integrate the phase phik(fτ) Phase phi of zero frequency subtractionk(0) To obtain the phase error phi 'in the sub-band'k(fτ)。
3. The method for estimating and compensating the multi-subband signal error of the high-resolution spaceborne SAR system according to claim 2, characterized in that: in S15, the first order compensation filter function H1,k(fτAnd n) the calculation method comprises the following steps:
H1,k(fτ,n)＝exp{j2π(fτ+fc,k)tk,n}
in the formula (f)τIs a distance frequency point;
fc,kthe central frequency point of the kth sub-band;
tk,nthe time delay of the nth strong point target data of the kth sub-band.
4. The method for multi-subband signal error estimation and compensation of a high resolution spaceborne SAR system according to claim 3, characterized in that: in S16, amplitude error A 'in each sub-band'k(fτ) The calculation method comprises the following steps:
Figure FDA0002892675030000021
in the formula, Ak(n,fτ) For the nth row frequency f of the kth sub-bandτProcessing the amplitude value;
n is the number of rows of each sub-band data and is also equal to the number of selected strong point targets;
fτis a distance frequency point;
b is the subband signal bandwidth.
5. The method for multi-subband signal error estimation and compensation of a high resolution spaceborne SAR system according to claim 4, characterized in that: in the step S17, a phase gradient is applied
Figure FDA0002892675030000022
The calculation method comprises the following steps:
Figure FDA0002892675030000031
in the formula, Sk(n,fτ) For the nth row frequency f of the kth sub-bandτA frequency domain signal function of the amplitude values;
S* k(n,fτ) Is Sk(n,fτ) The conjugate function of (a).
6. The method for multi-subband signal error estimation and compensation of a high resolution spaceborne SAR system according to claim 5, characterized in that: in the second step, the amplitude error Δ Ρ of the inter-subband signalkPhase error Δ αkAnd delay error Δ tkThe calculation method comprises the following steps:
s21, judging whether strong point targets exist or not line by line according to the sub-band imaging data, selecting data with the lines where the strong point targets exist, adding a rectangular window by taking the position where the strong point targets exist as the center, and setting pixel units outside the rectangular window to be zero; marking as strong point target data in the rectangular window;
s22, performing distance direction FFT on the strong point target data of each sub-band, and transforming the strong point target data into a distance frequency domain;
s23, calculating a quadratic compensation filter function H2,k(fτ) Respectively connecting the strong point target data of each sub-band with a secondary compensation filter function H2,k(fτ) Multiplying to realize amplitude and phase error compensation in the sub-band;
s24, transforming the compensated strong point target data to a distance time domain through IFFT;
s25, the strong point target data after interpolation of each sub-band is subjected to line-by-line judgment of peak value positions; obtaining the time delay t 'of the nth strong point target of the kth sub-band through the imaging parameters'k,n(ii) a Calculating the time delay error delta t of the kth sub-band relative to the 1 st sub-bandk：
Figure FDA0002892675030000032
S26, extracting the phase of each line peak position of the interpolated strong point target data of each sub-band, and obtaining the phase of the nth strong point target of the kth sub-band as alpha through the imaging parametersk,nCalculating the phase error Delta alpha of the kth sub-band relative to the 1 st sub-bandkComprises the following steps:
Figure FDA0002892675030000033
fc,kthe central frequency point of the kth sub-band; f. ofc,1The center frequency point of the 1 st sub-band;
s27, extracting the amplitude of each line peak position of the interpolated strong point target data of each sub-band, and obtaining the amplitude of the nth strong point target of the kth sub-band as P through the imaging parametersk,n(ii) a Computing the amplitude error Δ Ρ of the kth subband with respect to the 1 st subbandk：
Figure FDA0002892675030000041
Ρ1,nThe amplitude of the nth strong point target of the 1 st sub-band.
7. Root of herbaceous plantThe method for estimating and compensating the multi-subband signal error of the high-resolution spaceborne SAR system according to claim 6, characterized in that: in S23, the quadratic compensation filter function H2,k(fτ) The calculation method comprises the following steps:
H2,k(fτ)＝A′k(fτ)exp{-jΦ′k(fτ)}
of formula (II) to'k(fτ) The amplitude error in each sub-band;
Φ′k(fτ) Is the phase error within each subband.
8. The method for multi-subband signal error estimation and compensation of a high resolution spaceborne SAR system according to claim 7, characterized in that: in the third step, the specific method for performing error compensation on the multi-subband imaging data of the original data and performing multi-subband signal splicing comprises the following steps:
s31, transforming the original sub-band imaging data to a distance frequency domain through distance-direction FFT processing;
s32, in distance frequency domain, each sub-band signal and the quadratic compensation filter function H2,k(fτ) Multiplying to realize amplitude and phase error compensation in the sub-band;
s33, calculating a cubic compensation filter function H3,k(fτ)：
Figure FDA0002892675030000042
Each sub-band signal is combined with a cubic compensation filter function H3,k(fτ) Multiplying to realize amplitude, phase and time delay error compensation among the sub-bands;
s34, expanding the distance frequency domain to be larger than the total bandwidth of the multi-sub-band signal, and cutting and moving the effective distance frequency spectrum of each sub-band to the expanded distance frequency domain, wherein the frequency spectrum amount delta f of the k sub-band to be movedc,kComprises the following steps:
Δfc,k＝fc,k-fc
and S35, transforming the synthesized distance frequency domain signal into a distance time domain through distance to IFFT, and obtaining the full-resolution SAR image.
CN202110031851.2A 2021-01-11 2021-01-11 Multi-subband signal error estimation and compensation method for high-resolution spaceborne SAR system Active CN112859122B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202110031851.2A CN112859122B (en) 2021-01-11 2021-01-11 Multi-subband signal error estimation and compensation method for high-resolution spaceborne SAR system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202110031851.2A CN112859122B (en) 2021-01-11 2021-01-11 Multi-subband signal error estimation and compensation method for high-resolution spaceborne SAR system

Publications (2)

Publication Number Publication Date
CN112859122A true CN112859122A (en) 2021-05-28
CN112859122B CN112859122B (en) 2022-10-21

Family

ID=76002489

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202110031851.2A Active CN112859122B (en) 2021-01-11 2021-01-11 Multi-subband signal error estimation and compensation method for high-resolution spaceborne SAR system

Country Status (1)

Country Link
CN (1) CN112859122B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113740821A (en) * 2021-09-14 2021-12-03 中国人民解放军国防科技大学 Estimation and compensation method for satellite-borne P-band SAR two-dimensional space-variant scintillation phase error

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104316924A (en) * 2014-10-15 2015-01-28 南京邮电大学 Autofocus motion compensation method of airborne ultra-high resolution SAR (Synthetic Aperture Radar) back projection image
CN104635221A (en) * 2015-03-05 2015-05-20 北京航空航天大学 Sub-band splicing method based on internal calibration data
CN111722225A (en) * 2020-06-28 2020-09-29 南京航空航天大学 Bistatic SAR two-dimensional self-focusing method based on prior phase structure information

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104316924A (en) * 2014-10-15 2015-01-28 南京邮电大学 Autofocus motion compensation method of airborne ultra-high resolution SAR (Synthetic Aperture Radar) back projection image
CN104635221A (en) * 2015-03-05 2015-05-20 北京航空航天大学 Sub-band splicing method based on internal calibration data
CN111722225A (en) * 2020-06-28 2020-09-29 南京航空航天大学 Bistatic SAR two-dimensional self-focusing method based on prior phase structure information

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
JINCHENG LI ET AL.: "A Synthetic Bandwidth Method for High-Resolution SAR Based on PGA in the Range Dimension", 《SENSORS》 *
张梅等: "频带合成机载SAR的运动补偿", 《电子与信息学报》 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113740821A (en) * 2021-09-14 2021-12-03 中国人民解放军国防科技大学 Estimation and compensation method for satellite-borne P-band SAR two-dimensional space-variant scintillation phase error

Also Published As

Publication number Publication date
CN112859122B (en) 2022-10-21

Similar Documents

Publication Publication Date Title
CN103954938B (en) Multi-sub-band reception synthetic method for SAR echo signals
US6384773B1 (en) Adaptive fragmentation and frequency translation of continuous spectrum waveform to make use of discontinuous unoccupied segments of communication bandwidth
CN103728591A (en) MIMO radar near-field target efficient real beam direction focusing method
CN101984363B (en) Ultrahigh-resolution synthetic aperture radar (SAR) imaging method based on frequency-stepped system
CN110488285B (en) Non-interrupt bistatic SAR (synthetic aperture radar) phase synchronization signal processing method based on coding signal
CN112859122B (en) Multi-subband signal error estimation and compensation method for high-resolution spaceborne SAR system
CN110988875A (en) Multi-sub-band frequency spectrum splicing and synthesizing method of ultrahigh-resolution satellite-borne SAR system
CN110095787B (en) SAL full-aperture imaging method based on MEA and deramp
CN106842198A (en) A kind of subband fusion of imaging algorithm based on convex optimum theory
Adjemov et al. Methods and algorithms of broadband HF signals dispersion distortion compensation
Lobova et al. Experimental results of dispersion distortion compensation of wideband signals with a device based on a digital filter bank
CN106842196A (en) A kind of azimuth ambiguity suppression method for SAR sub-aperture images
CN111175747B (en) Phase error estimation method based on multichannel complex image space
CN116520261B (en) Bistatic SAR phase synchronous interference suppression method based on blind source separation
DE102017104380A1 (en) Radar system and method for operating a radar system
JP3740657B2 (en) Synthetic aperture radar apparatus and image reproducing method thereof
CN113419241B (en) Signal reconstruction method and equipment
CN107255809B (en) Blocking array beam forming method based on broadband focusing matrix
CN115220008A (en) Broadband radar target energy accumulation method based on sub-band processing
US20110237198A1 (en) Method and System for Super-Resolution Blind Channel Modeling
CN113938358B (en) Time delay determination method and terminal
CN113740821A (en) Estimation and compensation method for satellite-borne P-band SAR two-dimensional space-variant scintillation phase error
CN112180370A (en) SAR range-oriented reference signal processing method and device
CN115037404B (en) Array signal delay compensation method under GPU platform
CN111157964A (en) Robust broadband frequency domain channel correction method based on singular value decomposition

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant