Vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion

Abstract

The application discloses a kind of vehicle-mounted video SAR imaging methods based on sub-aperture spectrum fusion, comprising: establishing vehicle-mounted SAR sub-aperture imaging model, and determining the instantaneous slant range of arbitrary point P under "walk-stop" assumption;After the difference frequency processing of each sub-aperture signal and transmission signal, difference frequency signal is obtained, and signal after range compression is obtained;The range compressed signal is subjected to azimuth Fourier transform, and two-dimensional frequency domain signal is obtained;Two-dimensional frequency domain signal is subjected to inverse distance Fourier transform and distance curvature compensation, and signal after range migration correction is obtained;The range migration corrected signal is subjected to distance Fourier transform and azimuth compression, and two-dimensional focused first signal is obtained;First frame image is generated using the first M first signals and azimuth compensation function, and the first signal of the i frame and the i-1 frame image overlap, the latest first signal and the time sequence offset function are used to generate the i (i>1) Frame image.The application solves the imaging distortion problem caused by space variation.

Description

Technical Field

[0001] The present invention belongs to the technical field of radar signal processing, and in particular relates to a vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion. Background Art

[0002] Autonomous driving technology, a key development direction for the future automotive industry, has garnered widespread attention. Autonomous driving relies on real-time, high-precision, and highly reliable perception of the road traffic environment. Millimeter-wave radar, a core sensor in autonomous driving systems, can measure radial distance and velocity with high precision. However, its angular resolution is limited by the actual antenna array aperture and sensor cost. Consequently, its angular resolution cannot meet the spatial resolution requirements of a driving environment.

[0003] Synthetic Aperture Radar (SAR) technology utilizes vehicle motion to create a large antenna aperture, overcoming the limitations of actual antenna apertures and enabling high-resolution, two-dimensional imaging of targets. However, existing SAR imaging requires a certain synthetic aperture time to achieve high-resolution, two-dimensional imaging, significantly limiting its real-time performance.

[0004] Video SAR imaging overcomes this contradiction in traditional SAR imaging, enabling continuous multi-frame output while meeting the real-time requirements of driving scenarios. Currently, most video SAR utilizes backprojection imaging algorithms and their extensions. While these single-pulse imaging results can be reused, avoiding data recalculation, the computational complexity remains significant, placing a significant burden on hardware processing. Furthermore, existing sub-aperture coherent stitching methods can still suffer from image aliasing in strip-mode vehicle-mounted SAR imaging.

[0005] Therefore, it is crucial to design a video SAR implementation method suitable for the automotive platform and solve the space-variation problem in vehicle-mounted SAR imaging scenarios. Summary of the Invention

[0006] In order to solve the above problems existing in the prior art, the present invention provides a vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0007] The present invention provides a vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion, which is applied to synthetic aperture radar SAR;

[0008] The method comprises:

[0009] Establish a subaperture imaging model for vehicle-borne SAR in strip mode and determine the instantaneous slant range of any point P in the ground scene under the "stop-go" assumption;

[0010] For each received sub-aperture signal, perform difference frequency processing on it and the transmitted signal, calculate the difference frequency signal at any point P according to the instantaneous slant range, and use the difference frequency signal to obtain a range-compressed signal;

[0011] According to the stationary phase theorem, the range-compressed signal is subjected to azimuth Fourier transform to obtain a two-dimensional frequency domain signal;

[0012] Performing a range-direction inverse Fourier transform on the two-dimensional frequency domain signal and performing range bending compensation in sections to obtain a range migration corrected signal;

[0013] performing range Fourier transform and azimuth compression on the signal after range migration correction to obtain a first signal after two-dimensional focusing;

[0014] Before use M The first signal and the orientation compensation function generate a first frame image, and the first frame image is generated by the first i Frame image and i- The first signal of the overlapping 1 frame image, the first signal of the latest acquisition and the timing offset function are used to generate the first i ( i >1) frame image.

[0015] In one embodiment of the present invention, the instantaneous slant distance of any point P in the ground scene under the "stop-go" assumption is:

[0016]

[0017] in, represents the minimum instantaneous slope distance of any point P, Indicates the speed of the car. represents the azimuth time of the subaperture, represents the central moment of the subaperture, represents the position of the arbitrary point P, Indicates the instantaneous slant distance.

[0018] In one embodiment of the present invention, the step of performing difference frequency processing on each received sub-aperture signal and the transmitted signal, calculating the difference frequency signal at any point P according to the instantaneous slant range, and obtaining a range-compressed signal using the difference frequency signal includes:

[0019] Perform difference frequency processing on each received sub-aperture signal and the transmitted signal, and calculate the difference frequency signal at the arbitrary point P according to the instantaneous slant range:

[0020]

[0021] Where, represents the time domain window function of the azimuth dimension, represents the time domain window function of the distance dimension, Indicates fast time, is the carrier frequency of the transmitted signal, represents the speed of light, Indicates the frequency modulation of the transmitted signal. is the imaginary unit, is the difference frequency signal at any point P;

[0022] The difference frequency signal is subjected to distance Fourier transform and residual video phase compensation to obtain a distance compressed signal. :

[0023]

[0024] Where, Indicates the pulse duration of the transmitted signal, represents the distance frequency, is the Symge function.

[0025] In one embodiment of the present invention, the two-dimensional frequency domain signal is:

[0026] Where, represents the azimuth frequency of the sub-aperture signal, represents the distance migration of the arbitrary point P, .

[0027] In one embodiment of the present invention, the step of performing range-direction inverse Fourier transform on the two-dimensional frequency domain signal and performing range warping compensation in sections to obtain a range migration corrected signal includes:

[0028] The two-dimensional frequency domain signal is subjected to inverse Fourier transform in the range direction according to the following formula to obtain the signal: :

[0029]

[0030] The sub-aperture data is divided into multiple distance blocks along the distance dimension, and the compensation function is used Perform distance bending compensation on each distance block segment, where:

[0031]

[0032] Indicates the The sub-aperture data includes sub-aperture signals of multiple arbitrary points at each distance unit;

[0033] The signal With the compensation function Multiply to get the signal after range migration correction :

[0034] .

[0035] In one embodiment of the present invention, the step of performing range Fourier transform and azimuth compression on the range migration corrected signal to obtain a two-dimensionally focused first signal comprises:

[0036] The signal after range migration correction Perform distance Fourier transform to obtain the signal :

[0037]

[0038] The signal Matching function with azimuth frequency domain Multiply and get the first signal after two-dimensional focusing ;in:

[0039]

[0040] .

[0041] In one embodiment of the present invention, the use of M The step of generating a first frame image using the first signal and an orientation compensation function includes:

[0042] For each of the two-dimensionally focused first signals , eliminating the sub-aperture center moment And with the orientation compensation function Multiply and get the signal ;in:

[0043]

[0044]

[0045] Will M signal Sub-aperture coherent stitching and azimuth inverse Fourier transform are performed to obtain the first frame of image.

[0046] In one embodiment of the present invention, the use of i Frame image and i- The first signal of the overlapping 1 frame image, the first signal of the latest acquisition and the timing offset function are used to generate the first i ( i >1) The steps of framing an image include:

[0047] Get the i Frame image and i- The first signal of a frame image overlaps and at the moment of eliminating its sub-aperture center Then multiplying it with the first timing offset function to obtain a second signal;

[0048] Get the latest recorded first signal and eliminate its sub-aperture center at the moment Then multiplying it with the second timing offset function to obtain a third signal;

[0049] The second signal and the third signal are coherently spliced ​​and azimuthally inverse Fourier transformed to obtain the first i ( i >1) frame image.

[0050] In one embodiment of the present invention, the first timing offset function is: , the second timing offset function is , Indicates the number of sub-apertures into which each frame image is divided.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] The present invention provides a vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion. When focusing the sub-aperture signal, range warping compensation is performed on a two-dimensional frequency domain signal after inverse Fourier transform in a segmented range migration correction manner to obtain a range-migration-corrected signal. This avoids the high computational complexity caused by sinc interpolation, thereby effectively improving the imaging distortion problem caused by scene space variation. In addition, in the spectrum fusion stage, the present invention achieves aliasing-free coherent splicing of each frame of image by introducing a timing offset function, avoiding the problem of repeated processing of overlapping data and greatly reducing the computational burden.

[0053] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is a flow chart of a vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion provided by an embodiment of the present invention;

[0055] Figure 2 is another flow chart of the vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion provided by an embodiment of the present invention;

[0056] Figure 3 1 is a schematic diagram of a vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion provided by an embodiment of the present invention;

[0057] Figure 4 This is a model diagram of a vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion provided by an embodiment of the present invention;

[0058] Figure 5 Schematic diagram of a point target simulation scenario provided by an embodiment of the present invention;

[0059] Figure 6a 1 is a schematic diagram of simulation results of a first frame of image provided by an embodiment of the present invention;

[0060] Figure 6b is a schematic diagram of simulation results of a second frame of image provided by an embodiment of the present invention;

[0061] Figure 6c is a schematic diagram of simulation results of the third frame image provided by an embodiment of the present invention;

[0062] Figure 6d is a schematic diagram of simulation results of the fourth frame image provided by an embodiment of the present invention;

[0063] Figure 6e is a schematic diagram of simulation results of the fifth frame image provided by an embodiment of the present invention;

[0064] Figure 6f 2 is a schematic diagram of simulation results of the sixth frame of image provided by an embodiment of the present invention;

[0065] Figure 7a This is a schematic diagram of the result of correcting curvature using the point approximation method provided by an embodiment of the present invention;

[0066] Figure 7b 2 is a schematic diagram of the result of correcting bending using the method of the present invention provided in an embodiment of the present invention;

[0067] Figure 7c 1 is a schematic diagram of the result of sinc interpolation correction for curvature provided by an embodiment of the present invention;

[0068] Figure 8a This is a contour map of a single sub-aperture focusing result obtained by using a vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion provided by PT1 in an embodiment of the present invention;

[0069] Figure 8b This is a contour map of the focusing result after two sub-aperture stitching obtained by PT1 provided in an embodiment of the present invention using a vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion;

[0070] Figure 8c This is a contour map of the focusing result after three sub-aperture stitching obtained by PT1 provided in an embodiment of the present invention using a vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion;

[0071] Figure 9ais an azimuth profile obtained by using a full-aperture algorithm for PT1 provided in an embodiment of the present invention;

[0072] Figure 9b The azimuth profile image obtained by the PT1 provided in an embodiment of the present invention using a vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion; DETAILED DESCRIPTION

[0073] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0074] Figure 1 This is a flow chart of a vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion provided by an embodiment of the present invention. Figure 1 As shown, an embodiment of the present invention provides a vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion, comprising:

[0075] S1. Establish a subaperture imaging model for vehicle-borne SAR in strip mode and determine the instantaneous slant range of any point P in the ground scene under the "stop-go" assumption.

[0076] S2. For each received sub-aperture signal, perform difference frequency processing on it and the transmitted signal to obtain a difference frequency signal at the arbitrary point P, and use the difference frequency signal to obtain a range-compressed signal;

[0077] S3. Using the stationary phase theorem, perform azimuth Fourier transform on the range-compressed signal to obtain a two-dimensional frequency domain signal;

[0078] S4, performing range-direction inverse Fourier transform on the two-dimensional frequency domain signal and performing range warping compensation in sections to obtain a signal corrected for range migration;

[0079] S5. Performing range Fourier transform and azimuth compression on the signal after range migration correction to obtain a first signal after two-dimensional focusing;

[0080] S6. Before use M The first signal and the orientation compensation function generate a first frame image, and the first frame image is generated by the first i Frame image and i- The first signal of the overlapping 1 frame image, the first signal of the latest acquisition and the timing offset function are used to generate the first i ( i >1) frame image.

[0081] It should be understood that during the transmission of the transmitted signal, the effect of the continuous movement of the radar on the echo signal can be approximately considered as the frequency offset of the center frequency of the transmitted signal. , the frequency offset is converted into a range offset :

[0082]

[0083] in, Indicates the center frequency of the transmitted signal, represents the transmit signal bandwidth, represents the frequency sweep period, Indicates the oblique angle of the transmitted signal at the time of transmission. According to the vehicle parameters in most cases, the maximum oblique distance offset is much smaller than the distance resolution unit. , so its influence can be ignored.

[0084] Based on the above analysis, the influence of fast time on instantaneous slant range can be ignored in vehicle-borne SAR imaging under the FMCW (Frequency Modulated Continuous Wave) system. That is, the “stop-go” assumption holds true. Then, the instantaneous slant range of any point P in the ground scene under the “stop-go” assumption is:

[0085]

[0086] in, represents the minimum slope distance of any point P, Indicates the speed of the car. represents the azimuth time of the subaperture, represents the central moment of the subaperture, represents the position of any point P, It represents the instantaneous slope distance of any point P.

[0087] Figure 2 This is another flow chart of the vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion provided by an embodiment of the present invention. Figure 2 In step S2, for each received sub-aperture signal, performing difference frequency processing on it and the transmitted signal to obtain a difference frequency signal at any point P, and using the difference frequency signal to obtain a range-compressed signal, the steps include:

[0088] S201. Perform difference frequency processing on each received sub-aperture signal and the transmitted signal, ignoring unimportant amplitude and phase terms, to obtain the difference frequency signal at any point P:

[0089]

[0090] Where, represents the time domain window function of the azimuth dimension, represents the time domain window function of the distance dimension, Indicates fast time, is the carrier frequency of the transmitted signal, represents the speed of light, Indicates the frequency modulation of the transmitted signal. is the imaginary unit, is the difference frequency signal at any point P;

[0091] S202, performing distance Fourier transform and residual video phase compensation on the difference frequency signal to obtain a distance compressed signal :

[0092]

[0093] Where, Indicates the signal pulse duration, represents the distance frequency, is the Symge function.

[0094] Signal after distance compression Perform azimuth Fourier transform to obtain a two-dimensional frequency domain signal :

[0095] Where, represents the azimuth frequency of the sub-aperture signal, represents the distance migration of the arbitrary point P, .

[0096] Optionally, in step S4, the step of performing inverse Fourier transform on the two-dimensional frequency domain signal and performing range warping compensation in sections to obtain a signal corrected for range migration includes:

[0097] According to the following formula, the two-dimensional frequency domain signal is transformed into the inverse Fourier transform to obtain the signal :

[0098]

[0099] The sub-aperture data is divided into multiple distance blocks along the distance dimension, and the compensation function is used Perform distance bending compensation on each distance block segment, where:

[0100]

[0101] Indicates the The reference distance of each range block, the sub-aperture data includes sub-aperture signals of multiple arbitrary points at each range unit;

[0102] The signal With the compensation function Multiply to get the signal after range migration correction :

[0103] .

[0104] Furthermore, the step of performing range Fourier transform and azimuth compression on the signal after range migration correction to obtain a two-dimensionally focused first signal includes:

[0105] The signal after range migration correction Perform distance Fourier transform to obtain the signal :

[0106]

[0107] The signal Matching function with azimuth frequency domain Multiply and get the first signal after two-dimensional focusing :

[0108] .

[0109] Figure 3 1 is a schematic diagram of a vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion provided by an embodiment of the present invention. Figure 4 This is a model diagram of the vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion provided by an embodiment of the present invention. Figure 3-4 When processing the first frame image, the above step S6 uses the previous M The step of generating a first frame image using a first signal and an orientation compensation function includes:

[0110] S601: For each first signal after two-dimensional focusing , eliminating the sub-aperture center moment And with the orientation compensation function Multiply and get the signal ;in:

[0111]

[0112]

[0113] S602, will M signal Perform sub-aperture coherent stitching and azimuth inverse Fourier transform to obtain the first frame image. In this step, M signal After sub-aperture coherent stitching and azimuthal inverse Fourier transform, any point P in the first frame image is represented as: , , They are M The bandwidth of the sub-aperture signal.

[0114] Further, processing i ( i >1) frame image, use the i Frame image and i- The first signal of the overlapping 1 frame image, the first signal of the latest acquisition and the timing offset function are used to generate the first i ( i >1) The steps of framing an image include:

[0115] S603, obtain the i Frame image and i- The first signal of a frame image overlaps and at the moment of eliminating its sub-aperture center Then multiplying it with the first timing offset function to obtain a second signal;

[0116] S604, obtain the latest recorded first signal and eliminate its sub-aperture center moment Then multiplying it with the second timing offset function to obtain a third signal;

[0117] S605, perform coherent splicing and azimuth inverse Fourier transform on the second signal and the third signal to obtain the first i ( i >1) frame image.

[0118] It should be noted that the i ( i >1) The processing of the frame image is different from that of the first frame image. i ( i >1) The frame image needs to be used with the i-1 Specifically, according to the ViSAR principle, the order of the overlapping first signals is shifted relative to the previous frame, so in this embodiment, the sub-aperture center moment of eliminating the overlapping first signal is After that, you need to use the first timing offset function To solve this problem, the first timing offset function .

[0119] For the first signal newly recorded, similarly, first eliminate its sub-aperture center moment Then with the second timing offset function Multiplication, second timing offset function , Indicates the number of sub-apertures into which each frame image is divided.

[0120] In the above step S503, the second signal and the third signal are coherently spliced ​​and azimuthally inverse Fourier transformed. i ( i >1) The frame image is represented as:

[0121] .

[0122] Next, the above-mentioned vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion is further illustrated through simulation experiments.

[0123] like Figure 5 As shown, the distance between the two targets is 3.2 meters, and the distance is 3 meters. Point target, the specific parameters are shown in Table 1:

[0124] Table 1

[0125]

[0126] In this embodiment, each frame image corresponds to 11 sub-apertures. According to the parameters in Table 1, it can be calculated that the vehicle-mounted video SAR frame rate is about 4 Hz, and the movement of each point target between two adjacent frames is 256 samples. Figures 6a-6f The simulation results shown in the figure show that the image information of ViSAR demonstration will change as the SAR platform moves. Figure 6b and Figure 6c , the position of the same point target such as PT2 in two adjacent frames of images has a 256 sample offset.

[0127] Since the target slant range is small in the case of vehicle-mounted SAR, the spatial variation in range migration compensation cannot be ignored. The comparison results of different range migration correction methods are shown in Figure 2. Figures 8a-8c As shown in Figure 2, four point targets A, B, C, and D with the same azimuth position are used to verify the effectiveness of the curved segment correction. Figure 7a Indicated by the red dotted line.

[0128] Figure 7a This is the simulation result of using the approximate method to correct the bending. It can be seen intuitively that only points B and C have achieved good bending correction results using the traditional method. Figure 7b and Figure 7c The simulation results of the method of the present invention and sinc interpolation correction bending are shown in Figure 2. Both methods can achieve good focusing results.

[0129] Figure 8a 、 8b 8c and 8d are contour maps of the focusing results of single sub-aperture, two sub-apertures and three sub-apertures after splicing obtained by PT1 using the vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion provided by an embodiment of the present invention, Figure 9a The azimuth profile obtained by using the full aperture algorithm of PT1 provided in the embodiment of the present invention, Figure 9bThis is the azimuth profile obtained by the PT1 provided in the embodiment of the present invention using the vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion. Further, the splicing method of the sub-aperture data is verified. Under the simulation parameters shown in Table 1, the full aperture length of the single point target is approximately 3 times the sub-aperture length, as shown in Table 1. Figures 8a-8c , 9a-9b The sub-aperture fusion method proposed in the present invention can achieve the resolution of full aperture processing.

[0130] Compared with the prior art, the present invention has the following beneficial effects:

[0131] The present invention provides a vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion. When focusing the sub-aperture signal, range warping compensation is performed on a two-dimensional frequency domain signal after inverse Fourier transform in a segmented range migration correction manner to obtain a range-migration-corrected signal. This avoids the high computational complexity caused by sinc interpolation, thereby effectively improving the imaging distortion problem caused by scene space variation. In addition, in the spectrum fusion stage, the present invention achieves aliasing-free coherent splicing of each frame of image by introducing a timing offset function, avoiding the problem of repeated processing of overlapping data and greatly reducing the computational burden.

[0132] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0133] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0134] Although the present application is described herein in conjunction with various embodiments, in the process of implementing the claimed application, those skilled in the art can understand and implement other variations of the disclosed embodiments by reviewing the drawings, the disclosure, and the appended claims.

[0135] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion, characterized in that: Applied to synthetic aperture radar SAR; The method comprises: Establish a subaperture imaging model for vehicle-borne SAR in strip mode and determine the instantaneous slant range of any point P in the ground scene under the "stop-go" assumption. For each received sub-aperture signal, perform difference frequency processing on it and the transmitted signal, calculate the difference frequency signal at any point P according to the instantaneous slant range, and use the difference frequency signal to obtain a range-compressed signal; According to the stationary phase theorem, the range-compressed signal is subjected to azimuth Fourier transform to obtain a two-dimensional frequency domain signal; Performing a range-direction inverse Fourier transform on the two-dimensional frequency domain signal and performing range bending compensation in sections to obtain a range migration corrected signal; performing range Fourier transform and azimuth compression on the signal after range migration correction to obtain a first signal after two-dimensional focusing; Before use M The first signal and the orientation compensation function generate a first frame image, and the first frame image is generated by the first i Frame image and i- The first signal of the overlapping 1 frame image, the first signal of the latest acquisition and the timing offset function are used to generate the first i ( i >1) frame image.

2. The vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion according to claim 1, characterized in that: The instantaneous slant range of any point P in the ground scene under the "stop-go" assumption is: in, represents the minimum instantaneous slope distance of any point P, Indicates the speed of the car. represents the azimuth time of the subaperture, represents the central moment of the subaperture, represents the position of the arbitrary point P, Indicates the instantaneous slant distance.

3. The vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion according to claim 2, characterized in that: The step of performing difference frequency processing on each received sub-aperture signal and the transmitted signal, calculating the difference frequency signal at any point P according to the instantaneous slant range, and obtaining a range-compressed signal using the difference frequency signal comprises: Perform difference frequency processing on each received sub-aperture signal and the transmitted signal, and calculate the difference frequency signal at the arbitrary point P according to the instantaneous slant range: Where, represents the time domain window function of the azimuth dimension, represents the time domain window function of the distance dimension, Indicates fast time, is the carrier frequency of the transmitted signal, represents the speed of light, Indicates the frequency modulation of the transmitted signal. is the imaginary unit, is the difference frequency signal at any point P; The difference frequency signal is subjected to distance Fourier transform and residual video phase compensation to obtain a distance compressed signal. : Where, Indicates the pulse duration of the transmitted signal, represents the distance frequency, is the Symge function.

4. The vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion according to claim 3, characterized in that: The two-dimensional frequency domain signal is: Where, represents the azimuth frequency of the sub-aperture signal, represents the distance migration of the arbitrary point P, .

5. The vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion according to claim 4, characterized in that: The step of performing inverse Fourier transform on the two-dimensional frequency domain signal and performing range warping compensation in sections to obtain a signal corrected for range migration includes: The two-dimensional frequency domain signal is subjected to inverse Fourier transform in the range direction according to the following formula to obtain the signal: : The sub-aperture data is divided into multiple distance blocks along the distance dimension, and the compensation function is used Perform distance bending compensation on each distance block segment, where: Indicates the The sub-aperture data includes sub-aperture signals of multiple arbitrary points at each distance unit; The signal With the compensation function Multiply to get the signal after range migration correction : 。 6. The vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion according to claim 5, characterized in that: The step of performing range Fourier transform and azimuth compression on the signal after range migration correction to obtain a two-dimensionally focused first signal comprises: The signal after range migration correction Perform distance Fourier transform to obtain the signal : The signal Matching function with azimuth frequency domain Multiply and get the first signal after two-dimensional focusing ;in: 。 7. The vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion according to claim 6, characterized in that: Before the use M The step of generating a first frame image using the first signal and an orientation compensation function includes: For each of the two-dimensionally focused first signals , eliminating the sub-aperture center moment And with the orientation compensation function Multiply and get the signal ;in: Will M signal Sub-aperture coherent stitching and azimuth inverse Fourier transform are performed to obtain the first frame of image.

8. The vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion according to claim 6, characterized in that: The use of i Frame image and i- The first signal of the overlapping 1 frame image, the first signal of the latest acquisition and the timing offset function are used to generate the first i ( i >1) The steps of framing an image include: Get the i Frame image and i- The first signal of a frame image overlaps and at the moment of eliminating its sub-aperture center Then multiplying it with the first timing offset function to obtain a second signal; Get the latest recorded first signal and eliminate its sub-aperture center at the moment Then multiplying it with the second timing offset function to obtain a third signal; The second signal and the third signal are coherently spliced ​​and azimuthally inverse Fourier transformed to obtain the first i ( i >1) frame image.

9. The vehicle-mounted video SAR imaging method based on sub-aperture spectrum fusion according to claim 8, characterized in that: The first timing offset function is: , the second timing offset function is , Indicates the number of sub-apertures into which each frame image is divided.

Images