A SAR real-time imaging preprocessing method and system

Abstract

The application discloses a SAR real-time imaging preprocessing method, comprising the following steps: acquiring original echo data; performing distance compression processing on the original echo data to obtain distance compressed echo; performing distance interception on the distance compressed echo according to a pre-configured image display area to obtain first interception echo; and performing transposition processing on the first interception echo; performing azimuth compression processing on the first interception echo after the transposition processing to obtain azimuth compressed echo; performing azimuth interception on the azimuth compressed echo according to the pre-configured image display area to obtain second interception echo, and performing transposition processing on the second interception echo; and sending the second interception echo after the transposition processing into a real-time imaging processor for real-time imaging processing. The application can reduce the data processing amount of the real-time imaging processor, and improve the calculation and transmission efficiency.

Description

Technical Field

[0001] This invention relates to the field of radar signal processing technology, and more specifically, to a SAR real-time imaging preprocessing method and system. Background Technology

[0002] In a real-time synthetic aperture radar (SAR) system, the radar front-end transmits microwave signals and receives reflected echo signals, forming raw echo data that is transmitted to a real-time imaging processor. The processor processes this raw echo data in real time to obtain a panoramic image, which is then transmitted to a ground-based display terminal. The display terminal then extracts a local portion of the panoramic image for display. However, because real-time SAR imaging resolution is generally very high, far exceeding the display capacity of the terminal window, users only need to view the area of ​​interest. However, the entire image is processed during real-time imaging, resulting in a significant waste of processing power and a very low effective computational ratio. Furthermore, transmitting the raw processing results requires substantial data bandwidth, leading to low data utilization.

[0003] No effective solutions have yet been proposed to address the problems in the relevant technologies. Summary of the Invention

[0004] To address the problems in related technologies, this invention proposes a SAR real-time imaging preprocessing method and system, which can reduce the amount of data processed by the real-time imaging processor and improve computation and transmission efficiency.

[0005] The technical solution of this invention is implemented as follows:

[0006] According to one aspect of the present invention, a SAR real-time imaging preprocessing method is provided.

[0007] This SAR real-time imaging preprocessing method includes:

[0008] Acquire raw echo data;

[0009] The original echo data is compressed in the range direction to obtain a range-compressed echo; according to the pre-configured image display area, the range-compressed echo is truncated in the range direction to obtain a truncated echo; and the truncated echo is transposed.

[0010] The transposed echo is subjected to azimuth compression to obtain azimuth compressed echo; according to the pre-configured image display area, the azimuth compressed echo is trunculated to obtain secondary trunculated echo, and the secondary trunculated echo is transposed.

[0011] The transposed echo is then sent to a real-time imaging processor for real-time imaging processing.

[0012] The original echo data is subjected to range compression processing, and the compression processing formula for the range compressed echo is as follows:

[0013] Data range (n, t)=ifft{fft{Data(n, t)}.*Hr(fx)}

[0014]

[0015] In the formula, Data range (n, t) represents the range-compressed processing result, Data(n, t) represents the original two-dimensional echo data, Hr(fx) is the range filter, fx is the range frequency, fft{} performs an FFT transform on the data, ifft{} performs an inverse FFT transform on the data, rect{} is the rectangular window function, exp{} is the natural exponential function, Kp is the pulse frequency modulation slope, and T p is the pulse duration; j is the imaginary number; π is pi.

[0016] Furthermore, according to the pre-configured image display area, the range-directed compressed echo is truncated in the range direction to obtain a truncated echo, which includes: determining the image start position and the display image size in the panoramic image according to the pre-configured image display area; determining the original echo truncating position according to the image start position and determining the range truncating length according to the display image size; and truncating the range-directed compressed echo in the range direction according to the original echo truncating position and the range truncating length to obtain a truncated echo.

[0017] The formula for determining the original echo interception position based on the image's starting position is as follows:

[0018] P r0 =floor(T) p ×Fr / 2)+P x0_img ×ML r

[0019] In the formula, F r The SAR baseband sampling rate is represented by floor(), which indicates the floor function. ML r For range-oriented multi-view processing factors, single-view processing is ML. r =1; P r0 P is the original echo interception position. x0_img The coordinates of the starting pixel point of the image in the X direction.

[0020] The formula for determining the distance cropping length based on the displayed image size is as follows:

[0021] P r_cut =floor(T)p ×F r )+P x_cut ×ML r

[0022] In the formula, F r The SAR baseband sampling rate is represented by floor(), which indicates the floor function. ML r For range-oriented multi-view processing factors, single-view processing is ML. r =1; P r_vut P is the length of the original echo distance cutoff. x_cut This refers to the position of the displayed image in the X direction.

[0023] The azimuth compression process is performed on the transposed echo, resulting in the following formula for the azimuth compressed echo:

[0024] Data azimuth (n, t) = ifft{fft{Data r_cut (n, t)}.*Ha(fy))}

[0025]

[0026] In the formula, Data azimuth (n, t) represents the data result after azimuth compression. r_cut (n, t) represents the original data after range truncation, Ha(fy) is the azimuth filter, and fy is the Doppler frequency; K a Here, j is the azimuth tuning frequency, j is the imaginary number, and π is the mathematical constant pi.

[0027] In addition, according to the pre-configured image display area, the azimuth compression echo is trunculated in the azimuth direction to obtain the secondary truncated echo, which includes: determining the direction sampling point and the display image size in the panoramic image according to the pre-configured image display area; taking the direction sampling point as the starting position and determining the azimuth truncation length according to the display image size, the azimuth compression echo is truncated in the azimuth direction to obtain the secondary truncated echo.

[0028] The formula for calculating the direction sampling point is as follows:

[0029] P a0 =N aptl / 2+P y0_img ×ML a

[0030] In the formula, N aptl The number of sampling points for a single synthetic aperture in the system, ML a For azimuth multi-view processing factor; P a0 For directional sampling points; Py0_img The coordinates of the starting pixel point of the image in the y-direction.

[0031] The formula for calculating the azimuth cropping length based on the displayed image size is as follows:

[0032] P a_cut =N aptl +P y_cut ×ML a

[0033] In the formula, N aptl The number of sampling points for a single synthetic aperture in the system, ML a For azimuth multi-view processing factor; P x_cut This represents the position of the displayed image in the y-direction.

[0034] According to another aspect of the present invention, a SAR real-time imaging preprocessing system is provided.

[0035] This SAR real-time imaging preprocessing system includes:

[0036] The data acquisition module is used to acquire raw echo data;

[0037] The range interception module is used to perform range compression processing on the original echo data to obtain a range compressed echo; according to the pre-configured image display area, it performs range interception on the range compressed echo to obtain a first intercepted echo; and it performs transpose processing on the first intercepted echo.

[0038] The azimuth interception module is used to perform azimuth compression processing on the transposed primary intercepted echo to obtain an azimuth compressed echo; according to the pre-configured image display area, the azimuth compressed echo is intercepted in the azimuth direction to obtain a secondary intercepted echo, and the secondary intercepted echo is transposed.

[0039] The data transmission module is used to send the transposed, secondary intercepted echo to the real-time imaging processor for real-time imaging processing.

[0040] The range interception module performs range compression processing on the original echo data, and the compression processing formula for the range-compressed echo is as follows:

[0041] Data range (n, t)=ifft{fft{Data(n, t)}.*Hr(fx)}

[0042]

[0043] In the formula, Data range(n, t) represents the range-compressed processing result, Data(n, t) represents the original two-dimensional echo data, Hr(fx) is the range filter, fx is the range frequency, fft{} performs an FFT transform on the data, ifft{} performs an inverse FFT transform on the data, rect{} is the rectangular window function, exp{} is the natural exponential function, Kp is the pulse frequency modulation slope, and T p is the pulse duration; j is the imaginary number; π is pi.

[0044] Furthermore, when the distance interception module performs distance interception on the distance-directed compressed echo according to the pre-configured image display area to obtain a single intercepted echo, it determines the image start position and the display image size in the panoramic image according to the pre-configured image display area; determines the original echo interception position according to the image start position, and determines the distance interception length according to the display image size; and performs distance interception on the distance-directed compressed echo according to the original echo interception position and the distance interception length to obtain a single intercepted echo.

[0045] The formula for determining the original echo interception position based on the image's starting position is as follows:

[0046] P r0 =floor(T) p ×F r / 2)+P x0_img ×ML r

[0047] In the formula, F r The SAR baseband sampling rate is represented by floor(), which indicates the floor function. ML r For range-oriented multi-view processing factors, single-view processing is ML. r =1; P r0 P is the original echo interception position. x0_img The coordinates of the starting pixel point of the image in the X direction.

[0048] The formula for determining the distance cropping length based on the displayed image size is as follows:

[0049] P r_cut =floor(T) p ×F r )+P x_cut ×ML r

[0050] In the formula, F r The SAR baseband sampling rate is represented by floor(), which indicates the floor function. ML r For range-oriented multi-view processing factors, single-view processing is ML. r =1; P r_vutP is the length of the original echo distance cutoff. x_cut This refers to the position of the displayed image in the X direction.

[0051] The azimuth interception module performs azimuth compression processing on the transposed primary intercepted echo, and the compression processing formula for the azimuth compressed echo is as follows:

[0052] Data azimuth (n, t) = ifft{fft{Data r_cut (n, t)}.*Ha(fy))}

[0053]

[0054] In the formula, Data azimuth (n, t) represents the data result after azimuth compression. r_cut (n, t) represents the original data after range truncation, Ha(fy) is the azimuth filter, and fy is the Doppler frequency; K a Here, j is the azimuth tuning frequency, j is the imaginary number, and π is the mathematical constant pi.

[0055] In addition, when the azimuth interception module performs azimuth interception on the azimuth compressed echo according to the pre-configured image display area to obtain the secondary intercepted echo, it determines the direction sampling point and the display image size in the panoramic image according to the pre-configured image display area; takes the direction sampling point as the starting position, and determines the azimuth interception length according to the display image size, and performs azimuth interception on the azimuth compressed echo to obtain the secondary intercepted echo.

[0056] The formula for calculating the direction sampling point is as follows:

[0057] P a0 =N aptl / 2+P y0_img ×ML a

[0058] In the formula, N aptl The number of sampling points for a single synthetic aperture in the system, ML a For azimuth multi-view processing factor; P a0 For directional sampling points; P y0_img The coordinates of the starting pixel point of the image in the y-direction.

[0059] The formula for calculating the azimuth cropping length based on the displayed image size is as follows:

[0060] P a_cut =N aptl +P y_cut ×ML a

[0061] In the formula, N aptl The number of sampling points for a single synthetic aperture in the system, ML a For azimuth multi-view processing factor; P x_cut This represents the position of the displayed image in the y-direction.

[0062] Beneficial effects:

[0063] This invention reduces the amount of data processed by the real-time imaging processor by processing only a portion of the raw data, thus significantly reducing computational load and lowering the requirements for the SAR system processor. Simultaneously, because only a local image is transmitted, the size of the transmitted data is reduced, thereby significantly decreasing the amount of data transmitted and reducing the bandwidth requirements for data transmission. The final display result is obtained after the real-time imaging processor completes its processing, eliminating the need for cropping from the global image. Attached Figure Description

[0064] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0065] Figure 1 This is a flowchart illustrating a SAR real-time imaging preprocessing method according to an embodiment of the present invention.

[0066] Figure 2 This is a structural block diagram of a SAR real-time imaging preprocessing system according to an embodiment of the present invention;

[0067] Figure 3 This is a schematic diagram of data arrangement according to an embodiment of the present invention. Detailed Implementation

[0068] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0069] According to an embodiment of the present invention, a SAR real-time imaging preprocessing method and system are provided.

[0070] like Figure 1 As shown, a SAR real-time imaging preprocessing method according to an embodiment of the present invention includes step S101, acquiring raw echo data;

[0071] Step S103: Perform range compression processing on the original echo data to obtain range compressed echo; perform range truncation on the range compressed echo according to the pre-configured image display area to obtain a first truncated echo; and perform transpose processing on the first truncated echo.

[0072] Step S105: Perform azimuth compression processing on the transposed primary truncated echo to obtain an azimuth compressed echo; according to the pre-configured image display area, perform azimuth truncation on the azimuth compressed echo to obtain a secondary truncated echo, and perform transpose processing on the secondary truncated echo.

[0073] Step S107: The transposed secondary captured echo is sent to the real-time imaging processor for real-time imaging processing.

[0074] like Figure 2 As shown, a SAR real-time imaging preprocessing system according to an embodiment of the present invention includes a data acquisition module 201 for acquiring raw echo data;

[0075] The range interception module 203 is used to perform range compression processing on the original echo data to obtain a range compressed echo; to perform range interception on the range compressed echo according to a pre-configured image display area to obtain a first intercepted echo; and to perform transpose processing on the first intercepted echo.

[0076] The azimuth interception module 205 is used to perform azimuth compression processing on the transposed primary intercepted echo to obtain an azimuth compressed echo; according to the pre-configured image display area, the azimuth compressed echo is intercepted in the azimuth direction to obtain a secondary intercepted echo, and the secondary intercepted echo is transposed.

[0077] The data transmission module 207 is used to send the transposed secondary intercepted echo to the real-time imaging processor for real-time imaging processing.

[0078] In practical applications, transposition processing involves swapping the range and azimuth directions of the echo matrix. The purpose is to enable the processor to continuously read and write echo data and perform compression processing, thereby improving processing performance by increasing data reading efficiency. This is an existing processing technology and will not be elaborated on here.

[0079] The original echo data is then subjected to range compression processing, resulting in the range-compressed echo compression formula:

[0080] Data range (n, t)=ifft{fft{Data(n, t)}.*Hr(fx)}

[0081]

[0082] In the formula, Data range (n, t) represents the range-compressed processing result, Data(n, t) represents the original two-dimensional echo data, Hr(fx) is the range filter, fx is the range frequency, fft{} performs an FFT transform on the data, ifft{} performs an inverse FFT transform on the data, rect{} is the rectangular window function, exp{} is the natural exponential function, and K... p T is the pulse frequency modulation slope. p is the pulse duration; j is the imaginary number; π is pi.

[0083] When performing range-direction truncation on the range-direction compressed echo according to the pre-configured image display area to obtain a truncated echo, the starting position of the image and the size of the displayed image in the panoramic image can be determined according to the pre-configured image display area; the original echo truncation position can be determined according to the image starting position, and the range truncation length can be determined according to the size of the displayed image; the range-direction compressed echo can be truncated according to the original echo truncation position and the range truncation length to obtain a truncated echo.

[0084] The formula for determining the original echo interception position based on the image's starting position is: P r0 =floor(T) p ×F r / 2)+P x0_img ×ML r In the formula, F r The SAR baseband sampling rate is represented by floor(), which indicates the floor function. ML r For range-oriented multi-view processing factors, single-view processing is ML. r =1; P r0 P is the original echo interception position. x0_img Let P be the coordinates of the starting pixel point of the image in the X direction. The formula for calculating the distance to be cropped, based on the displayed image size, is: P r_cut =floor(T) p ×F r )+P x_cut ×ML r In the formula, F r The SAR baseband sampling rate is represented by floor(), which indicates the floor function. ML r For range-oriented multi-view processing factors, single-view processing is ML. r =1; P r_cut P is the length of the original echo distance cutoff. x_cut This refers to the position of the displayed image in the X direction.

[0085] In practical applications, the azimuth compression process is performed on the first-order truncated echo after transposition, and the compression formula for the azimuth compressed echo is as follows:

[0086] Data azimuth (n, t) = ifft{fft{Data r_cut (n, t)}.*Ha(fy))}

[0087]

[0088] In the formula, Data azimuth (n, t) represents the data result after azimuth compression. r_cut (n, t) represents the original data after range truncation, Ha(fy) is the azimuth filter, and fy is the Doppler frequency; K a Here, j is the azimuth tuning frequency, j is the imaginary number, and π is the mathematical constant pi.

[0089] When performing azimuth truncation on the azimuth compressed echo according to the pre-configured image display area to obtain a secondary truncated echo, the directional sampling point and the display image size in the panoramic image can be determined according to the pre-configured image display area; the directional sampling point is used as the starting position, and the azimuth truncation length is determined according to the display image size, and the azimuth compressed echo is truncated to obtain a secondary truncated echo.

[0090] The formula for calculating the direction sampling point is: P a0 =N aptl / 2+P y0_img ×ML a In the formula, N aptl The number of sampling points for a single synthetic aperture in the system, ML a For azimuth multi-view processing factor; P a0 For directional sampling points; P y0_img Let P be the coordinates of the starting pixel point of the image in the y-direction. Based on the displayed image size, the formula for calculating the azimuth cropping length is: P a_cut =N aptl +P y_cut ×ML a In the formula, N aptl The number of sampling points for a single synthetic aperture in the system, ML a For azimuth multi-view processing factor; P x_cut This represents the position of the displayed image in the y-direction.

[0091] To facilitate understanding of the above technical solutions of the present invention, specific examples are provided below to further illustrate the above technical solutions of the present invention.

[0092] by Figure 3Taking the data arrangement shown as an example, the raw echo data is arranged in two dimensions, with the range × azimuth magnitudes being N respectively. range =32768, N azimuth =32768, each sampling point is a single-precision floating-point complex number (size is 8 bytes), and the real-time imaging processor processes 8Gbytes of data.

[0093] Range-oriented multi-view factor (ML) r The azimuth multi-view factor is 4. a Pulse duration T p The baseband sampling rate is 2µs. r For 1.024GHz, T p ×F r The value is 4096, N aptl Given 2048, the panoramic image size can be calculated to be P. width =7168, P height =15360.

[0094] Without real-time preprocessing, all raw data must always be processed. When viewing a panoramic image on a display terminal, the display area occupies 100% of the panoramic image, with a data redundancy of 1. When viewing a 1024x1024 image on a display terminal, the display area occupies 0.95% of the panoramic image, with a data redundancy of 105 times.

[0095] When using real-time preprocessing, the raw data to be processed varies depending on the size of the display area. When viewing a panoramic image on a monitor, the display area occupies 100% of the screen, and the data redundancy is 1. When viewing a 1024x1024 image on a monitor, P can be obtained. r_cut For 8192, P a_cut The real-time imaging processor processes 256 MBytes of data, which is 3.125% of the original data. The data redundancy is 3.28 times, and the efficiency is 32 times higher than that of directly processing all the original echo data.

[0096] As can be seen from the above, when the display area occupies a small proportion of the global image, the real-time preprocessing module can significantly improve the efficiency of the original data.

[0097] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A SAR real-time imaging preprocessing method, characterized in that, include: Acquire raw echo data; The original echo data is compressed in the range direction to obtain a range-compressed echo; according to the pre-configured image display area, the range-compressed echo is truncated in the range direction to obtain a truncated echo; and the truncated echo is transposed. The transposed echo is subjected to azimuth compression to obtain azimuth compressed echo; according to the pre-configured image display area, the azimuth compressed echo is trunculated to obtain secondary trunculated echo, and the secondary trunculated echo is transposed. The transposed echo is then sent to a real-time imaging processor for real-time imaging processing. The pre-configured image display area is a local image area to be displayed by the display terminal in the panoramic image; According to a pre-configured image display area, the range-directed compressed echo is truncated in the range direction to obtain a truncated echo. This includes: determining the image start position and the display image size in the panoramic image according to the pre-configured image display area; determining the original echo truncating position according to the image start position and the range truncating length according to the display image size; and truncating the range-directed compressed echo in the range direction according to the original echo truncating position and the range truncating length to obtain a truncated echo. The process of azimuthally truncating the azimuthally compressed echo according to the pre-configured image display area to obtain a secondary truncated echo includes: determining the direction sampling point and the display image size in the panoramic image according to the pre-configured image display area; taking the direction sampling point as the starting position and determining the azimuth truncation length according to the display image size, and truncating the azimuthally compressed echo to obtain a secondary truncated echo.

2. The SAR real-time imaging preprocessing method according to claim 1, characterized in that, The original echo data is subjected to range compression processing, and the compression processing formula for the range compressed echo is as follows: In the formula, This is the result of distance compression. The original two-dimensional echo data is a range-direction filter. For distance frequency, To perform FFT transformation on the data, To perform the inverse FFT transformation on the data, } is a rectangular window function. It is a natural exponential function. The slope of the pulse frequency modulation. The duration of the pulse; It is an imaginary number; Pi is the mathematical constant of a circle.

3. The SAR real-time imaging preprocessing method according to claim 1, characterized in that, The formula for determining the original echo cutoff position based on the starting position of the image is as follows: In the formula, This represents the SAR baseband sampling rate. This indicates a round-down operation. For distance-oriented multi-view processing factors, single-view processing is... ; This is the location where the original echo was intercepted; The coordinates of the starting pixel point of the image in the X direction.

4. The SAR real-time imaging preprocessing method according to claim 3, characterized in that, The formula for calculating the distance cropping length, based on the size of the displayed image, is as follows: In the formula, This represents the SAR baseband sampling rate. This indicates a round-down operation. For distance-oriented multi-view processing factors, single-view processing is... ; The length is the cutoff value for the original echo distance; This refers to the position of the displayed image in the X direction.

5. The SAR real-time imaging preprocessing method according to claim 4, characterized in that, The azimuth compression process is applied to the transposed echo, and the compression formula for the azimuth compressed echo is as follows: In the formula, This is the result of azimuth compression. This is the data after the original data has been cropped by distance. For azimuth filters, The frequency is the Doppler frequency. For azimuth frequency tuning, It is an imaginary number; it is pi (π).

6. The SAR real-time imaging preprocessing method according to claim 1, characterized in that, The formula for calculating the directional sampling points is: In the formula, The number of sampling points for a single synthetic aperture in the system is denoted by , and the azimuth multi-view processing factor is denoted by . For directional sampling points; The coordinates of the starting pixel point of the image in the y-direction.

7. The SAR real-time imaging preprocessing method according to claim 6, characterized in that, Based on the displayed image size, the formula for calculating the azimuth cropping length is as follows: In the formula, The number of sampling points for a single synthetic aperture in the system. As a azimuth-oriented multi-view processing factor; This represents the position of the displayed image in the y-direction.

8. A SAR real-time imaging preprocessing system, characterized in that, include: The data acquisition module is used to acquire raw echo data; The range interception module is used to perform range compression processing on the original echo data to obtain a range compressed echo; according to the pre-configured image display area, it performs range interception on the range compressed echo to obtain a first intercepted echo; and it performs transpose processing on the first intercepted echo. The azimuth interception module is used to perform azimuth compression processing on the transposed primary intercepted echo to obtain an azimuth compressed echo; according to the pre-configured image display area, the azimuth compressed echo is intercepted in the azimuth direction to obtain a secondary intercepted echo, and the secondary intercepted echo is transposed. The data transmission module is used to send the transposed, secondary intercepted echo to the real-time imaging processor for real-time imaging processing. The pre-configured image display area is a local image area to be displayed by the display terminal in the panoramic image; According to a pre-configured image display area, the range-directed compressed echo is truncated in the range direction to obtain a truncated echo. This includes: determining the image start position and the display image size in the panoramic image according to the pre-configured image display area; determining the original echo truncating position according to the image start position and the range truncating length according to the display image size; and truncating the range-directed compressed echo in the range direction according to the original echo truncating position and the range truncating length to obtain a truncated echo. The process of azimuthally truncating the azimuthally compressed echo according to the pre-configured image display area to obtain a secondary truncated echo includes: determining the direction sampling point and the display image size in the panoramic image according to the pre-configured image display area; taking the direction sampling point as the starting position and determining the azimuth truncation length according to the display image size, and truncating the azimuthally compressed echo to obtain a secondary truncated echo.

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