CN113820713B - Imaging method, device and storage medium for transmitter-moving double-base arc array SAR - Google Patents

Abstract

The disclosure relates to the imaging method, device and storage medium of the transmitter moving double-base arc array SAR. Based on the assumption that the echo data has been demodulated by the baseband, the range to Fourier transform is performed to obtain the range, frequency, azimuth, and time domain echoes. wave data; through the decomposed bibase instantaneous slant distance to generate the range walking correction function, the distance walking correction is performed on the range frequency domain, azimuth and time domain echo data, and then the range pulse compression is performed; then the range and azimuth decoupling processing and the range inverse Fu Liye transform, after obtaining the decoupled two-dimensional time domain signal, perform azimuth Fourier transform and azimuth matching filtering, and then perform azimuth inverse Fourier transform after obtaining the azimuth pulse compressed signal to obtain the final Two-dimensional time-domain focused signal. Through various embodiments of the present disclosure, aiming at the bistatic arc array SAR system with transmitter motion, omnidirectional and high-resolution imaging can be obtained through high-order approximation of slant range, range walking compensation, and Keystone transformation.

Description

Imaging method, device and storage medium for transmitter-moving double-base arc array SAR

technical field

The disclosure relates to the technical field of radar interferometry data processing, and in particular to an imaging method for a transmitter moving bibase arc array SAR, an imaging device for a transmitter moving bibase arc array SAR, and a computer-readable storage medium.

Background technique

In the prior art, previous scholars proposed a back projection algorithm and a Range Doppler (RD) imaging algorithm based on Keystone transform for arc array SAR imaging processing. The back-projection algorithm is a time-domain algorithm. There is no approximate processing in the algorithm process, and it can obtain accurate images and meet the requirements of higher imaging quality. But its computation load is too large, and the imaging processing speed is slow. The RD algorithm based on the Keystone transform uses the Keystone transform to correct the range migration during the imaging process, which eliminates the coupling between the range and the azimuth, and can meet the imaging quality requirements of the airborne high-altitude flight. However, during the imaging process of the dual-base arc array SAR with the transmitter moving, the Doppler frequency of the target changes not only with the distance position, but also with the azimuth position. The obtained data has two-dimensional spatial variability, which increases the imaging Dealing with difficulty. On the other hand, the movement of the transmitter will cause a serious range walk, and the Keystone transform algorithm cannot be used to obtain a well-focused image, so the previous algorithm cannot be directly applied to the bistatic arc array SAR imaging of the transmitter movement.

Contents of the invention

The present disclosure intends to provide an imaging method for a transmitter moving bibase arc array SAR, an imaging device for a transmitter moving bibase arc array SAR, and a computer-readable storage medium, aiming at a transmitter moving bibase arc array SAR system , through the high-order approximation of slant distance, distance walking compensation, and Keystone transformation, the system's imaging processing is realized, and all-round, high-resolution imaging can be obtained.

According to one of the solutions of the present disclosure, there is provided an imaging method for a transmitter-moving dual-base arc array SAR, including:

Obtain the echo data of the transmitter moving double-base arc array SAR, and based on the assumption that the echo data has been demodulated by the baseband, perform a range-to-Fourier transform on the echo data to obtain azimuth time in the range-frequency domain domain echo data;

Generate a distance walking correction function through the decomposed bibase instantaneous slant distance, and use the distance walking correction function to perform distance walking correction on the range, frequency domain, azimuth and time domain echo data;

Perform range pulse compression on the range frequency domain signal after range walking correction;

Based on the range-to-pulse-compressed signal, the range-azimuth decoupling process and the range-to-inverse Fourier transform are performed to obtain a decoupled two-dimensional time-domain signal;

Perform azimuth Fourier transform and azimuth matched filtering on the two-dimensional time-domain signal to obtain the pulse-compressed azimuth signal;

The azimuth pulse-compressed signal is subjected to azimuth inverse Fourier transform to obtain the final two-dimensional time-domain focused signal.

In some embodiments, the distance walking correction function is generated by the decomposed bibase instantaneous slant distance, and the distance walking correction function is used to perform distance walking correction on the distance frequency domain azimuth time domain echo data, including:

Based on the hypothetical arbitrary target, the equivalent sampling point of the receiver, and the coordinates of the transmitter, the first instantaneous slant distance from the radar transmitter to the target is obtained;

The first instantaneous slant distance is approximated by Taylor series expansion, decomposed into two parts related to speed and independent of speed;

Generate a distance walking correction function according to the approximated first instantaneous slant distance;

The distance walking correction function is used to perform distance walking correction processing on the distance frequency domain, azimuth and time domain echo data, and the distance walking corrected echo data is obtained.

In some embodiments, the range-wise pulse compression is performed on the range-frequency domain signal after range walking correction processing, including:

A pulse compression function is constructed by means of matched filtering;

Using the obtained pulse compression function, the range pulse compression processing is performed on the echo signal in the range frequency domain, and the echo signal after range pulse compression is obtained.

In some embodiments, performing range-azimuth decoupling processing and range-to-inverse Fourier transform based on the range-to-pulse-compressed signal to obtain a decoupled two-dimensional time-domain signal, including:

Using Taylor series expansion to approximate the second instantaneous slant distance from the equivalent sampling point to the target, and obtain the approximated second instantaneous slant distance;

Using the Keystone transformation method to redefine a virtual azimuth sampling variable based on the approximated second instantaneous slant distance obtained above;

Perform Keystone transformation according to the redefined virtual azimuth variable to obtain the echo signal decoupled from the distance and azimuth;

The range and azimuth decoupled echo signals are subjected to range inverse Fourier transform to obtain the two-dimensional time domain signal after the range and azimuth decoupling.

In some embodiments, performing azimuth Fourier transform and azimuth matched filtering on the two-dimensional time domain signal to obtain azimuth pulse-compressed signals, including:

Perform azimuth Fourier transform on the two-dimensional time domain signal to obtain the echo signal in the range Doppler domain;

Construct the azimuth matched filter function convolution kernel, the convolution kernel is the phase item related to the redefined virtual azimuth variable in the two-dimensional time domain signal;

Generate an azimuth matched filter convolution kernel according to the two-dimensional time domain signal;

Perform azimuth Fourier transform and complex conjugate processing on the obtained convolution kernel to obtain the azimuth matched filter function;

Based on the obtained azimuth matched filter function, the range Doppler domain echo signal is processed by azimuth matched filter to obtain azimuth pulse compressed signal.

According to one of the solutions of the present disclosure, there is provided an imaging device for a bistatic arc array SAR with transmitter movement, including:

An acquisition module configured to acquire the echo data of the transmitter motion bibase arc array SAR;

A signal processing module configured to perform a range-to-Fourier transform on the echo data based on the assumption that the echo data has been subjected to baseband demodulation processing to obtain echo data in the range-frequency domain, azimuth, and time domain; after decomposing The distance walking correction function is generated by the bibase instantaneous slant distance, and the distance walking correction function is used to perform distance walking correction on the range frequency domain, azimuth and time domain echo data; the range frequency domain signal after the range walking correction processing is used for range pulse compression; Perform range and azimuth decoupling processing and range inverse Fourier transform based on the range pulse compressed signal to obtain a decoupled two-dimensional time domain signal; perform azimuth Fourier transform and azimuth matching on the two-dimensional time domain signal Filtering is used to obtain the compressed signal of the azimuth pulse; the azimuth inverse Fourier transform is performed on the compressed signal of the azimuth pulse to obtain the final two-dimensional time-domain focused signal.

In some embodiments, wherein, the signal processing module is further configured to:

The distance walking correction function is generated by the decomposed bibase instantaneous slant distance, and the distance walking correction function is used to perform distance walking correction on the range, frequency domain, azimuth and time domain echo data, including:

Based on the hypothetical arbitrary target, the equivalent sampling point of the receiver, and the coordinates of the transmitter, the first instantaneous slant distance from the radar transmitter to the target is obtained;

The first instantaneous slant distance is approximated by Taylor series expansion, decomposed into two parts related to speed and independent of speed;

Generate a distance walking correction function according to the approximated first instantaneous slant distance;

The distance walking correction function is used to perform distance walking correction processing on the distance frequency domain, azimuth and time domain echo data, and the distance walking corrected echo data is obtained.

In some embodiments, wherein, the signal processing module is further configured to:

Perform range pulse compression on the range frequency domain signal after range walking correction processing, including:

A pulse compression function is constructed by means of matched filtering;

Using the obtained pulse compression function, the range pulse compression processing is performed on the echo signal in the range frequency domain, and the echo signal after range pulse compression is obtained.

In some embodiments, wherein, the signal processing module is further configured to:

Based on the range pulse compressed signal, the range and azimuth decoupling processing and the range inverse Fourier transform are performed to obtain the decoupled two-dimensional time domain signal, including:

Using Taylor series expansion to approximate the second instantaneous slant distance from the equivalent sampling point to the target, and obtain the approximated second instantaneous slant distance;

Using the Keystone transformation method to redefine a virtual azimuth sampling variable based on the approximated second instantaneous slant distance obtained above;

According to the redefined virtual azimuth variable, the Keystone transformation is used to obtain the echo signal after the distance and azimuth decoupling;

The range and azimuth decoupled echo signals are subjected to range inverse Fourier transform to obtain the two-dimensional time domain signal after the range and azimuth decoupling.

According to one of the solutions of the present disclosure, a computer-readable storage medium is provided, on which computer-executable instructions are stored, and when the computer-executable instructions are executed by a processor, it can realize:

According to the imaging method of the bistatic arc array SAR with the transmitter moving above.

The imaging method of the transmitter moving bistatic arc array SAR, the imaging device of the transmitter moving bibase arc array SAR, and the computer-readable storage medium in various embodiments of the present disclosure obtain the transmitter moving bibase arc array SAR Based on the assumption that the echo data has been processed by baseband demodulation, range-to-Fourier transform is performed on the echo data to obtain echo data in the range-frequency domain, azimuth, and time domain; The distance walking correction function is generated based on the instantaneous slant distance, and the distance walking correction function is used to perform distance walking correction on the distance frequency domain, azimuth and time domain echo data; the range frequency domain signal after the distance walking correction processing is used for range pulse compression; based on the distance Perform range and azimuth decoupling processing and range inverse Fourier transform to the pulse-compressed signal to obtain the decoupled two-dimensional time domain signal; perform azimuth Fourier transform and azimuth matched filtering on the two-dimensional time domain signal, The azimuth pulse-compressed signal is obtained; the azimuth pulse-compressed signal is subjected to azimuth inverse Fourier transform to obtain the final two-dimensional time-domain focused signal. The present disclosure is aimed at the dual-base arc array SAR system with transmitter movement, realizes imaging processing of the system through high-order approximation of slant distance, distance walking compensation, and Keystone transformation, and can obtain omnidirectional and high-resolution imaging. Each embodiment of the present disclosure first performs high-order approximation processing on the bistatic slant distance through Taylor series expansion, and decomposes the slant distance into two parts, one part is independent of the transmitter speed, and the other part is related to the transmitter speed. According to the solved slant range formula, the range walk compensation function is constructed, and the range walk caused by the transmitter operation is corrected in the range frequency domain, which reduces the two-dimensional coupling of the echo signal. On this basis, the Keystone transformation is used to eliminate the remaining coupling between distance and azimuth. Finally, through azimuth matching filtering, a well-focused image is obtained.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure, as claimed.

Description of drawings

In the drawings, which are not necessarily to scale, like reference numerals may identify like components in the different views. Similar reference numbers with letter suffixes or with different letter suffixes may indicate different instances of similar components. The drawings illustrate various embodiments, generally by way of example and not limitation, and together with the description and claims serve to explain the disclosed embodiments.

FIG. 1 shows a signal processing flow chart of an embodiment of the imaging method of the transmitter-moving bistatic arc array SAR of the present disclosure.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings of the embodiments of the present disclosure. Apparently, the described embodiments are some of the embodiments of the present disclosure, not all of them. Based on the described embodiments of the present disclosure, all other embodiments obtained by persons of ordinary skill in the art without creative effort fall within the protection scope of the present disclosure.

Unless otherwise defined, the technical terms or scientific terms used in the present disclosure shall have the usual meanings understood by those skilled in the art to which the present disclosure belongs. "Comprising" or "comprising" and similar words mean that the elements or items appearing before the word include the elements or items listed after the word and their equivalents, without excluding other elements or items.

To keep the following description of the embodiments of the present disclosure clear and concise, detailed descriptions of known functions and known components are omitted from the present disclosure.

Arc array synthetic aperture radar (Synthetic Aperture Radar, SAR) is a new imaging system proposed in recent years. The system arranges the antenna array along the arc in the azimuth direction, which breaks through the problem of single observation angle of traditional linear array SAR. The rapid imaging perception of the 360° scene area around the airborne platform provides a guarantee for the safe flight and vertical take-off and landing of the helicopter platform, and has great application prospects in the civil and military fields. The double-base arc array SAR refers to placing the transmitter and receiver on different platforms. Compared with the single-base arc array SAR, the double-base arc array SAR has better concealment and security, and can obtain more Rich target information. Due to the separation of the transceiver platform and the flexible geometric structure of the double-base arc array SAR, different imaging modes can be set to meet different application requirements, for example, the double-base arc array SAR with the receiver moving, and the double-base arc array with the transmitter moving Array SAR, bi-base arc array SAR that transmits and receives movement. In the bistatic arc array SAR system where the transmitter moves, the receiver is fixed at a certain height. When it is set to the "silent" working mode, the concealment of the system can be improved, and the transmitter moves over the scene to expand the radiation range. , It can also make multiple low-cost receiving systems share the same expensive transmitting system, which not only ensures the safety of the airborne, but also reduces the system cost. Therefore, the application of bistatic arc array SAR to airborne navigation, assisted landing, blind landing and other fields has great application prospects.

Combining with the foregoing descriptions of background technology, the present disclosure exemplifies corresponding solutions in the form of embodiments to solve the defects existing in the prior art, but is not intended to limit the protection scope of the patent right claimed by the present disclosure.

As one of the schemes, an embodiment of the present disclosure provides an imaging method for a bistatic arc array SAR with transmitter movement, including:

Obtain the echo data of the transmitter moving double-base arc array SAR, and based on the assumption that the echo data has been demodulated by the baseband, perform a range-to-Fourier transform on the echo data to obtain azimuth time in the range-frequency domain domain echo data;

Generate a distance walking correction function through the decomposed bibase instantaneous slant distance, and use the distance walking correction function to perform distance walking correction on the range, frequency domain, azimuth and time domain echo data;

Perform range pulse compression on the range frequency domain signal after range walking correction;

Based on the range-to-pulse-compressed signal, the range-azimuth decoupling process and the range-to-inverse Fourier transform are performed to obtain a decoupled two-dimensional time-domain signal;

Perform azimuth Fourier transform and azimuth matched filtering on the two-dimensional time-domain signal to obtain the pulse-compressed azimuth signal;

The azimuth pulse-compressed signal is subjected to azimuth inverse Fourier transform to obtain the final two-dimensional time-domain focused signal.

In view of the problems raised above, various embodiments of the present disclosure aim to propose an imaging method for a bistatic arc array SAR with a transmitter moving. This method is aimed at the bistatic arc array SAR system with transmitter movement, and realizes the imaging processing of the system through high-order approximation of slant range, range walking compensation, and Keystone transformation, and can obtain omnidirectional and high-resolution imaging. The algorithm first performs high-order approximation processing on the bistatic slant range through Taylor series expansion, and decomposes the slant range into two parts, one part is independent of the transmitter speed, and the other part is related to the transmitter speed. According to the resolved slant range formula, the range walk compensation function is constructed, and the range walk caused by the transmitter motion is corrected in the range frequency domain, which reduces the two-dimensional coupling of the echo signal. On this basis, the Keystone transformation is used to eliminate the remaining coupling between distance and azimuth. Finally, through azimuth matching filtering, a well-focused image is obtained.

As shown in FIG. 1 , specific implementation steps may include but not limited to step S1 to step S6 as an example for illustration.

Specific implementation can include:

Step S1: Obtain the echo data s(t _r ,t _a ) of the transmitter moving bistatic arc array SAR. Assuming that the data has been demodulated by baseband, the echo data s(t _r ,t _a ) to perform range-to-Fourier transform, that is, use the following formula (1) to calculate and obtain the echo data S _s ( _fr , t _a ) in the range-frequency domain and azimuth time domain:

S _s (f _r ,t _a )=RFFT{s(t _r ,t _a )} (1)

In the formula (1), RFFT{ } represents the range Fourier transform, t _r is the time variable in the range direction, t _a is the time variable in the azimuth direction, and _fr is the range frequency.

In some embodiments, the present disclosure can be realized as follows: generating a distance walking correction function through the decomposed bibase instantaneous slant distance, and using the distance walking correction function to perform distance walking correction on the distance frequency domain azimuth time domain echo data, including:

Based on the hypothetical arbitrary target, the equivalent sampling point of the receiver, and the coordinates of the transmitter, the first instantaneous slant distance from the radar transmitter to the target is obtained;

The first instantaneous slant distance is approximated by Taylor series expansion, decomposed into two parts related to speed and independent of speed;

Generate a distance walking correction function according to the approximated first instantaneous slant distance;

The distance walking correction function is used to perform distance walking correction processing on the distance frequency domain, azimuth and time domain echo data, and the distance walking corrected echo data is obtained.

Specific implementation can include:

Step S2: Generate a range walk correction function from the decomposed bibase instantaneous slant distance, and use this function to perform range walk correction on the range-frequency domain echo data S _s ( _fr ,t _a ), the specific steps are as follows.

Step S21: Assume that the coordinates of any target, receiver equivalent sampling point, and transmitter are (θ _n , R _n , H _n ), (θ _r , R _r , H _r ), (θ _t , R _t , H _t ), then the instantaneous slant distance D _t from the radar transmitter to the target can be expressed as:

Among them, v is the moving speed of the transmitter, and t _a is the azimuth time variable.

Step S22: Use Taylor series expansion to approximate the above instantaneous slant distance D _t and decompose it into two parts related to speed and independent of speed:

D _t ≈κ ₀ +κ ₁ (vt _a )+κ ₂ (vt _a ) ² +κ ₃ (vt _a ) ³ +κ ₄ (vt _a ) ⁴ (3) where k ₀ , k ₁ , k ₂ , k ₃ and k ₄ are constant coefficients after resolution, and the calculation formulas of each coefficient are as follows:

In the formula, R _t and R _n are the ground distances between the transmitter and the target and the coordinate origin, H _t is the horizontal height of the transmitter, θ _t and θ _n are the azimuth angles of the transmitter and the target respectively.

Step S23: According to the instantaneous slope distance obtained in step S22, a distance walking correction function is generated, and the specific formula is as follows:

Step S24: Use the distance walking correction function generated in step S23 to perform distance walking correction processing on the echo data in the range frequency domain, and obtain the echo data S _s1 ( _fr , t _a ) after distance walking correction. The specific operation is as follows: As shown in (10):

S _s1 (fr _r ,t _a )=S _s (fr _r ,t _a )·h _c (fr _r ,t _a ) (10)

In formula (10), S _s ( _fr , t _a ) is the echo data in the range frequency domain, and h _c ( _fr , t _a ) is the range walking correction function.

In some embodiments, the present disclosure can be implemented as: performing range pulse compression on the range frequency domain signal after range walking correction processing, including:

A pulse compression function is constructed by means of matched filtering;

Using the obtained pulse compression function, the range pulse compression processing is performed on the echo signal in the range frequency domain, and the echo signal after range pulse compression is obtained.

Specific implementation can include:

Step S3: Perform range-wise pulse compression on the above-mentioned range-frequency domain signal S _s1 ( _fr ,t _a ) after range walking correction processing, and the specific processing process is as follows.

Step S31: Construct the pulse compression function H _r (f _r ) by means of matched filtering, specifically as follows:

In the formula, K _r is the range modulation frequency, T _r is the pulse width of the transmitted signal, and f _r is the range frequency.

Step S32: Using the pulse compression function H _r (f _r ) obtained in step S31, perform range pulse compression processing on the echo signal in the range frequency domain, and obtain the echo signal S _{sf_c} ( _fr ,t after range pulse compression _a ):

S _{sf_c} (f _r ,t _a )=S _s1 (f _r ,t _a )·H _r (f _r ) (12)

In formula (12), S _s1 ( _fr , t _a ) is the range-frequency domain signal after range walking correction, and H _r ( _fr ) is the range-wise pulse compression function.

In some embodiments, the present disclosure can be implemented as: performing range-azimuth decoupling processing and range-to-inverse Fourier transform based on the range-to-pulse-compressed signal to obtain a decoupled two-dimensional time-domain signal, including:

Using Taylor series expansion to approximate the second instantaneous slant distance from the equivalent sampling point to the target, and obtain the approximated second instantaneous slant distance;

Using the Keystone transformation method to redefine a virtual azimuth sampling variable based on the approximated second instantaneous slant distance obtained above;

According to the redefined virtual azimuth variable, the Keystone transformation is used to obtain the echo signal after the distance and azimuth decoupling;

The range and azimuth decoupled echo signals are subjected to range inverse Fourier transform to obtain the two-dimensional time domain signal after the range and azimuth decoupling.

Specific implementation can include:

Step S4: Step S4 performs range and azimuth decoupling processing and range inverse Fourier transform based on the signal after the range pulse compression to obtain a decoupled two-dimensional time domain signal. The specific processing process is as follows:

Step S41: Use Taylor series expansion to approximate the instantaneous slope distance D _r from the equivalent sampling point to the target, and obtain the approximate instantaneous slope distance D _r as shown in formula (13):

In the formula, H _r is the horizontal height of the equivalent sampling point, R _r is the radius of the arc array antenna, θ _r is the azimuth angle of the equivalent sampling point, β _r is the insertion angle, and it satisfies

Step S41: Redefine a virtual azimuth sampling variable based on the instantaneous slant distance D _r obtained above using the Keystone transformation method where /> The relationship with the azimuth sampling variable θ _r is shown in formula (14):

In the formula, f _c is the carrier frequency, f _r is the range frequency, θ _n is the azimuth angle of the target, and the relationship between the azimuth sampling variable θ _r and the azimuth time variable is shown in formula (15):

θ _r = ω _a t _a (15)

In the formula, ω _a is the switching speed of the receiver arc array antenna unit.

Step S42: according to the azimuth variable redefined in step S41 Use formula (16) to perform Keystone transformation to obtain the echo signal after decoupling range and azimuth/>

In the formula, S _{sf_c} ( _fr ,θ _r )| is the range-frequency domain signal after range pulse compression, and θ _n is the target azimuth angle.

Step S43: Perform range inverse Fourier transform on the range-frequency domain signal after the Keystone transform to obtain a two-dimensional time-domain signal decoupled from range and azimuth The specific calculation formula is shown in formula (17):

In the formula, RIFFT{ } represents the range inverse Fourier transform, is the range-frequency domain signal after Keystone transformation, t _r is the time variable in the range direction, and f _r is the range frequency.

In some embodiments, the present disclosure can be implemented as: performing azimuth Fourier transform and azimuth matched filtering on a two-dimensional time-domain signal to obtain azimuth pulse-compressed signals, including:

Perform azimuth Fourier transform on the two-dimensional time domain signal to obtain the echo signal in the range Doppler domain;

Construct the azimuth matched filter function convolution kernel, the convolution kernel is the phase item related to the redefined virtual azimuth variable in the two-dimensional time domain signal;

Generate an azimuth matched filter convolution kernel according to the two-dimensional time domain signal;

Perform azimuth Fourier transform and complex conjugate processing on the obtained convolution kernel to obtain the azimuth matched filter function;

Based on the obtained azimuth matched filter function, the range Doppler domain echo signal is processed by azimuth matched filter to obtain azimuth pulse compressed signal.

Specific implementation can include:

Step S5: For the two-dimensional time domain signal obtained above Carry out azimuth Fourier transform and azimuth matched filtering to obtain azimuth pulse compressed signal, the specific steps are as follows:

Step S51: For the two-dimensional time domain signal obtained in step S43 Perform azimuth Fourier transform to obtain range Doppler domain echo signal/> The specific calculation is shown in formula (18):

In the formula, AFFT{ } is the azimuth Fourier transform, is the two-dimensional time-domain signal obtained by formula (17).

Step S52: Construct the convolution kernel of the azimuth matched filter function as The convolution kernel is a two-dimensional time domain signal in and /> the relevant phase term;

Step S53: Generate azimuth matched filter convolution kernel according to the two-dimensional time domain signal of formula (17) Its specific expression is shown in formula (19):

In the above formula, f _c is the carrier frequency, is the azimuth virtual sampling variable redefined in step S41.

Step S54: Perform azimuth Fourier transform and complex conjugate processing on the convolution kernel obtained above to obtain the azimuth matched filter function The specific calculation formula is as follows:

In the above formula, AFFT { } is the azimuth Fourier transform, and { } ^* is the complex conjugate operation.

Step S55: Based on the azimuth pulse compression function obtained above, the range Doppler signal Carry out azimuth matched filter processing, the specific calculation process is shown in formula (21), and the azimuth direction pulse compressed signal is obtained

Step S6 can be implemented as: for the range Doppler signal obtained above Perform azimuth inverse Fourier transform to obtain the final two-dimensional time-domain focused signal/> The specific calculation process is shown in the following formula:

As one of the schemes, an embodiment of the present disclosure provides an imaging device for a bistatic arc array SAR with transmitter movement, including:

An acquisition module configured to acquire the echo data of the transmitter motion bibase arc array SAR;

A signal processing module configured to perform a range-to-Fourier transform on the echo data based on the assumption that the echo data has been subjected to baseband demodulation processing to obtain echo data in the range-frequency domain, azimuth, and time domain; after decomposing The distance walking correction function is generated by the bibase instantaneous slant distance, and the distance walking correction function is used to perform distance walking correction on the range frequency domain, azimuth and time domain echo data; the range frequency domain signal after the range walking correction processing is used for range pulse compression; Perform range and azimuth decoupling processing and range inverse Fourier transform based on the range pulse compressed signal to obtain a decoupled two-dimensional time domain signal; perform azimuth Fourier transform and azimuth matching on the two-dimensional time domain signal Filtering is used to obtain the compressed signal of the azimuth pulse; the azimuth inverse Fourier transform is performed on the compressed signal of the azimuth pulse to obtain the final two-dimensional time-domain focused signal.

As an implementation manner, the signal processing module of the disclosed device can be further configured in combination with the description of step S2 above:

The distance walking correction function is generated by the decomposed bibase instantaneous slant distance, and the distance walking correction function is used to perform distance walking correction on the range, frequency domain, azimuth and time domain echo data, including:

Based on the hypothetical arbitrary target, the equivalent sampling point of the receiver, and the coordinates of the transmitter, the first instantaneous slant distance from the radar transmitter to the target is obtained;

The first instantaneous slant distance is approximated by Taylor series expansion, decomposed into two parts related to speed and independent of speed;

Generate a distance walking correction function according to the approximated first instantaneous slant distance;

The distance walking correction function is used to perform distance walking correction processing on the distance frequency domain, azimuth and time domain echo data, and the distance walking corrected echo data is obtained.

As an implementation manner, the signal processing module of the disclosed device may be further configured as follows in combination with the description of step S3 above:

Perform range pulse compression on the range frequency domain signal after range walking correction processing, including:

A pulse compression function is constructed by means of matched filtering;

Using the obtained pulse compression function, the range pulse compression processing is performed on the echo signal in the range frequency domain, and the echo signal after range pulse compression is obtained.

As an implementation manner, the signal processing module of the disclosed device may be further configured in combination with the description of step S4 above:

Based on the range pulse compressed signal, the range and azimuth decoupling processing and the range inverse Fourier transform are performed to obtain the decoupled two-dimensional time domain signal, including:

Using Taylor series expansion to approximate the second instantaneous slant distance from the equivalent sampling point to the target, and obtain the approximated second instantaneous slant distance;

Using the Keystone transformation method to redefine a virtual azimuth sampling variable based on the approximated second instantaneous slant distance obtained above;

According to the redefined virtual azimuth variable, the Keystone transformation is used to obtain the echo signal after the distance and azimuth decoupling;

The range and azimuth decoupled echo signals are subjected to range inverse Fourier transform to obtain the two-dimensional time domain signal after the range and azimuth decoupling.

As an implementation manner, the signal processing module of the disclosed device can be further configured in combination with the description of step S5 above:

Perform azimuth Fourier transform and azimuth matched filtering on the two-dimensional time-domain signal to obtain the azimuth pulse-compressed signal, including:

Perform azimuth Fourier transform on the two-dimensional time domain signal to obtain the echo signal in the range Doppler domain;

Construct the azimuth matched filter function convolution kernel, the convolution kernel is the phase item related to the redefined virtual azimuth variable in the two-dimensional time domain signal;

Generate an azimuth matched filter convolution kernel according to the two-dimensional time domain signal;

Perform azimuth Fourier transform and complex conjugate processing on the obtained convolution kernel to obtain the azimuth matched filter function;

Based on the obtained azimuth matched filter function, the range Doppler domain echo signal is processed by azimuth matched filter to obtain azimuth pulse compressed signal.

Specifically, one of the inventive concepts of the present disclosure aims to obtain the echo data of the transmitter moving bibase arc array SAR, and based on the assumption that the echo data has been demodulated by the baseband, the echo The range-to-Fourier transform is performed on the data to obtain the range-frequency-domain, azimuth-time-domain echo data; the range-walking correction function is generated through the decomposed bibase instantaneous slant distance, and the distance-walking correction function is used to convert the range-frequency-domain, azimuth, and time-domain echo data Carry out range walking correction; perform range pulse compression on the range frequency domain signal after range walking correction processing; perform range and azimuth decoupling processing and range inverse Fourier transform based on the range pulse compressed signal to obtain the decoupled The two-dimensional time-domain signal; carry out azimuth Fourier transform and azimuth matching filtering on the two-dimensional time-domain signal to obtain the azimuth pulse-compressed signal; perform azimuth inverse Fourier transform on the azimuth pulse-compressed signal , to obtain the final two-dimensional time-domain focused signal. The present disclosure is aimed at the dual-base arc array SAR system with transmitter movement, realizes imaging processing of the system through high-order approximation of slant distance, distance walking compensation, and Keystone transformation, and can obtain omnidirectional and high-resolution imaging. Each embodiment of the present disclosure first performs high-order approximation processing on the bistatic slant distance through Taylor series expansion, and decomposes the slant distance into two parts, one part is independent of the transmitter speed, and the other part is related to the transmitter speed. According to the resolved slant range formula, the range walk compensation function is constructed, and the range walk caused by the transmitter motion is corrected in the range frequency domain, which reduces the two-dimensional coupling of the echo signal. On this basis, the Keystone transformation is used to eliminate the remaining coupling between distance and azimuth. Finally, through azimuth matching filtering, a well-focused image is obtained. In various application scenarios, the various embodiments of the present disclosure can realize omni-directional and high-resolution observation and imaging of the bistatic arc array SAR when the transmitter is moving, and not only achieve good concealment and high security of the bi-base arc array SAR , rich target information and other imaging characteristics, and can also perform imaging processing on large scenes around the platform when the transmitter is moving, which improves the utilization rate of the system. The imaging method and transmitter The imaging device and the computer-readable storage medium of the moving bistatic arc array SAR can be applied in the fields of helicopter safe flight, ground survey, emergency landing and the like.

The present disclosure also provides a computer-readable storage medium, on which computer-executable instructions are stored, and when the computer-executable instructions are executed by a processor, it mainly realizes imaging according to the above-mentioned transmitter-moving double-base arc array SAR methods, including:

Obtain the echo data of the transmitter moving double-base arc array SAR, and based on the assumption that the echo data has been demodulated by the baseband, perform a range-to-Fourier transform on the echo data to obtain azimuth time in the range-frequency domain domain echo data;

Generate a distance walking correction function through the decomposed bibase instantaneous slant distance, and use the distance walking correction function to perform distance walking correction on the range, frequency domain, azimuth and time domain echo data;

Perform range pulse compression on the range frequency domain signal after range walking correction;

Based on the range-to-pulse-compressed signal, the range-azimuth decoupling process and the range-to-inverse Fourier transform are performed to obtain a decoupled two-dimensional time-domain signal;

Perform azimuth Fourier transform and azimuth matched filtering on the two-dimensional time-domain signal to obtain the pulse-compressed azimuth signal;

The azimuth pulse-compressed signal is subjected to azimuth inverse Fourier transform to obtain the final two-dimensional time-domain focused signal.

In some embodiments, a processor that executes computer-executable instructions may be a processing device including one or more general-purpose processing devices, such as a microprocessor, a central processing unit (CPU), a graphics processing unit (GPU), and the like. More specifically, the processor may be a Complex Instruction Set Computing (CISC) microprocessor, a Reduced Instruction Set Computing (RISC) microprocessor, a Very Long Instruction Word (VLIW) microprocessor, a processor running other instruction sets, or A processor that runs a combination of instruction sets. The processor may also be one or more special-purpose processing devices, such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), digital signal processors (DSPs), system-on-chips (SoCs), and the like.

In some embodiments, the computer readable storage medium may be a memory such as read only memory (ROM), random access memory (RAM), phase change random access memory (PRAM), static random access memory (SRAM), Dynamic random access memory (DRAM), electrically erasable programmable read-only memory (EEPROM), other types of random access memory (RAM), flash disks or other forms of flash memory, caches, registers, static memory, CD-ROM only Read memory (CD-ROM), digital versatile disk (DVD) or other optical memory, cassette tape or other magnetic storage device, or any other possible non-transitory device used to store information or instructions that can be accessed by a computer device media etc.

In some embodiments, the computer-executable instructions can be implemented as a plurality of program modules, and the plurality of program modules jointly implement the signal processing method for medical images according to any one of the present disclosure.

The present disclosure describes various operations or functions, which may be implemented or defined as software codes or instructions. The display unit can be implemented as software codes or instruction modules stored in a memory, and when executed by a processor, corresponding steps and methods can be realized.

Such content may be source code for direct execution ("object" or "executable" form) or differential code ("delta" or "patch" code). A software implementation of the embodiments described herein may be provided by an article of manufacture having code or instructions stored thereon, or by a method of operating a communication interface to send data over the communication interface. A machine or computer-readable storage medium may cause the machine to perform the described functions or operations and includes any mechanism for storing information in a form accessible by the machine (e.g., computing display device, electronic system, etc.), such as recordable/non-recordable media (eg, read only memory (ROM), random access memory (RAM), magnetic disk storage media, optical storage media, flash memory display devices, etc.). Communication interfaces include any mechanism for interfacing with any of hardwired, wireless, optical, etc. media to communicate with other display devices, such as memory bus interfaces, processor bus interfaces, Internet connections, disk controllers, and the like. The communication interface may be configured to prepare the communication interface by providing configuration parameters and/or sending signals to provide data signals describing the software content. The communication interface can be accessed by sending one or more commands or signals to the communication interface.

The computer-executable instructions of embodiments of the present disclosure may be organized into one or more computer-executable components or modules. Aspects of the present disclosure can be implemented with any number and combination of such components or modules. For example, aspects of the present disclosure are not limited to the specific computer-executable instructions or the specific components or modules shown in the figures and described herein. Other embodiments may include different computer-executable instructions or components having more or less functionality than shown and described herein.

The above description is intended to be illustrative rather than restrictive. For example, the above examples (or one or more aspects thereof) may be used in combination with each other. For example, other embodiments may be used by those of ordinary skill in the art upon reading the above description. Additionally, in the above Detailed Description, various features may be grouped together in order to simplify the disclosure. This is not to be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, disclosed subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the detailed description as examples or embodiments, where each claim stands on its own as a separate embodiment, and it is contemplated that these embodiments may be combined with each other in various combinations or permutations. The scope of the disclosure should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

The above embodiments are only exemplary embodiments of the present disclosure, and are not intended to limit the present disclosure, and the protection scope of the present disclosure is defined by the claims. Those skilled in the art may make various modifications or equivalent replacements to the present disclosure within the spirit and protection scope of the present disclosure, and such modifications or equivalent replacements shall also be deemed to fall within the protection scope of the present disclosure.

Claims (10)

1. The imaging method of the bistatic arc array SAR with the transmitter moving, including: Obtain the echo data of the transmitter moving double-base arc array SAR, and based on the assumption that the echo data has been demodulated by the baseband, perform a range-to-Fourier transform on the echo data to obtain azimuth time in the range-frequency domain domain echo data; Generate a distance walking correction function through the decomposed bibase instantaneous slant distance, and use the distance walking correction function to perform distance walking correction on the range, frequency domain, azimuth and time domain echo data; Perform range pulse compression on the range frequency domain signal after range walking correction; Based on the range-to-pulse-compressed signal, the range-azimuth decoupling process and the range-to-inverse Fourier transform are performed to obtain a decoupled two-dimensional time-domain signal; Perform azimuth Fourier transform and azimuth matched filtering on the two-dimensional time-domain signal to obtain the pulse-compressed azimuth signal; Perform azimuth inverse Fourier transform on the azimuth pulse-compressed signal to obtain the final two-dimensional time-domain focused signal; Among them, the distance walking correction function is generated through the decomposed bibase instantaneous slant distance, and the distance walking correction function is used to perform distance walking correction on the range, frequency domain, azimuth and time domain echo data, including: The Taylor series expansion is used to approximate the first instantaneous slant distance from the radar transmitter to the target, and it is decomposed into two parts related to speed and independent of speed: κ ₀ and κ ₁ (vt _a )+κ ₂ (vt _a ) ² +κ ₃ (vt _a ) ³ +κ ₄ (vt _a ) ⁴ , k ₀ , k ₁ , k ₂ , k ₃ and k ₄ are based on The constant coefficients of any target, the equivalent sampling point of the receiver, and the coordinates of the transmitter; Based on the approximated first instantaneous slant distance, the distance walking correction function is generated: f _c is the carrier frequency, f _r is the range frequency, and t _a is the azimuth time variable. 2. The method according to claim 1, wherein, the distance walking correction function is generated by the bibase instantaneous slant distance after decomposition, and the distance walking correction is carried out to the distance frequency domain azimuth time domain echo data by using the distance walking correction function, and also includes : Based on the assumed arbitrary target, the equivalent sampling point of the receiver, and the coordinates of the transmitter, the first instantaneous slant distance is obtained; The range walking correction function is used to perform range walking correction processing on the range frequency domain, azimuth and time domain echo data, and the range walking corrected echo data is obtained. 3. The method according to claim 2, wherein performing range-to-pulse compression on the range-frequency-domain signal after range walking correction processing includes: A pulse compression function is constructed by means of matched filtering; Using the obtained pulse compression function, the range pulse compression processing is performed on the echo signal in the range frequency domain, and the echo signal after range pulse compression is obtained. 4. The method according to claim 3, wherein, based on the range-to-pulse-compressed signal, the range-azimuth decoupling process and the range-to-inverse Fourier transform are carried out to obtain a decoupled two-dimensional time-domain signal, comprising: Using Taylor series expansion to approximate the second instantaneous slant distance from the equivalent sampling point to the target, and obtain the approximated second instantaneous slant distance; Using the Keystone transformation method to redefine a virtual azimuth sampling variable based on the approximated second instantaneous slant distance obtained above; Perform Keystone transformation according to the redefined virtual azimuth variable to obtain the echo signal decoupled from the distance and azimuth; The range and azimuth decoupled echo signals are subjected to range inverse Fourier transform to obtain the two-dimensional time domain signal after the range and azimuth decoupling. 5. The method according to claim 4, wherein, carrying out azimuth Fourier transform and azimuth matched filtering to the two-dimensional time domain signal to obtain the azimuth pulse-compressed signal, comprising: Perform azimuth Fourier transform on the two-dimensional time domain signal to obtain the echo signal in the range Doppler domain; Construct the azimuth matched filter function convolution kernel, the convolution kernel is the phase item related to the redefined virtual azimuth variable in the two-dimensional time domain signal; Generate an azimuth matched filter convolution kernel according to the two-dimensional time domain signal; Perform azimuth Fourier transform and complex conjugate processing on the obtained convolution kernel to obtain the azimuth matched filter function; Based on the obtained azimuth matched filter function, the range Doppler domain echo signal is processed by azimuth matched filter to obtain azimuth pulse compressed signal. 6. The imaging device of the bistatic arc array SAR with transmitter movement, including: An acquisition module configured to acquire the echo data of the transmitter motion bibase arc array SAR; A signal processing module configured to perform a range-to-Fourier transform on the echo data based on the assumption that the echo data has been subjected to baseband demodulation processing to obtain echo data in the range-frequency domain, azimuth, and time domain; after decomposing The distance walking correction function is generated by the bibase instantaneous slant distance, and the distance walking correction function is used to perform distance walking correction on the range frequency domain, azimuth and time domain echo data; the range frequency domain signal after the range walking correction processing is used for range pulse compression; Perform range and azimuth decoupling processing and range inverse Fourier transform based on the range pulse compressed signal to obtain a decoupled two-dimensional time domain signal; perform azimuth Fourier transform and azimuth matching on the two-dimensional time domain signal Filtering to obtain the azimuth pulse-compressed signal; performing azimuth inverse Fourier transform on the azimuth pulse-compressed signal to obtain the final two-dimensional time-domain focused signal; Among them, the distance walking correction function is generated through the decomposed bibase instantaneous slant distance, and the distance walking correction function is used to perform distance walking correction on the range, frequency domain, azimuth and time domain echo data, including: The Taylor series expansion is used to approximate the first instantaneous slant distance from the radar transmitter to the target, and it is decomposed into two parts related to speed and independent of speed: κ ₀ and κ ₁ (vt _a )+κ ₂ (vt _a ) ² +κ ₃ (vt _a ) ³ +κ ₄ (vt _a ) ⁴ , k ₀ , k ₁ , k ₂ , k ₃ and k ₄ are based on The constant coefficients of any target, the equivalent sampling point of the receiver, and the coordinates of the transmitter; Based on the approximated first instantaneous slant distance, the distance walking correction function is generated: f _c is the carrier frequency, f _r is the range frequency, and t _a is the azimuth time variable. 7. The device according to claim 6, wherein the signal processing module is further configured to: The distance walking correction function is generated by the decomposed bibase instantaneous slant distance, and the distance walking correction function is used to perform distance walking correction on the range, frequency domain, azimuth and time domain echo data, including: Based on the assumed arbitrary target, the equivalent sampling point of the receiver, and the coordinates of the transmitter, the first instantaneous slant distance is obtained; The distance walking correction function is used to perform distance walking correction processing on the distance frequency domain, azimuth and time domain echo data, and the distance walking corrected echo data is obtained. 8. The device according to claim 7, wherein the signal processing module is further configured to: Perform range pulse compression on the range frequency domain signal after range walking correction processing, including: A pulse compression function is constructed by means of matched filtering; Using the obtained pulse compression function, the range pulse compression processing is performed on the echo signal in the range frequency domain, and the echo signal after range pulse compression is obtained. 9. The device according to claim 8, wherein the signal processing module is further configured to: Based on the range pulse compressed signal, the range and azimuth decoupling processing and the range inverse Fourier transform are performed to obtain the decoupled two-dimensional time domain signal, including: Using Taylor series expansion to approximate the second instantaneous slant distance from the equivalent sampling point to the target, and obtain the approximated second instantaneous slant distance; Using the Keystone transformation method to redefine a virtual azimuth sampling variable based on the approximated second instantaneous slant distance obtained above; According to the redefined virtual azimuth variable, the Keystone transformation is used to obtain the echo signal after the distance and azimuth decoupling; The range and azimuth decoupled echo signals are subjected to range inverse Fourier transform to obtain the two-dimensional time domain signal after the range and azimuth decoupling. 10. A computer-readable storage medium, on which computer-executable instructions are stored, and when the computer-executable instructions are executed by a processor, it realizes: The imaging method of the transmitter-moving double base arc array SAR according to any one of claims 1 to 5.