Outward-facing circular aperture radar space-varying phase compensation imaging method, device and storage medium

Abstract

This disclosure relates to a method, apparatus, and storage medium for outward-facing circular aperture radar with space-varying phase compensation imaging. The method includes: dividing a digital elevation model into several imaging spaces with different heights based on the different heights of the target area; and coherently superimposing the images in different imaging spaces after compensation based on the height of the imaging space to obtain a radar image. Through the various embodiments of this disclosure, errors caused by space-varying phase are compensated using a digital elevation model, thus solving the problem of decreased imaging accuracy caused by height-based space-varying phase.

Description

Technical Field

[0001] This disclosure relates to the field of radar signal processing, specifically to an outward-facing circular aperture radar space-varying phase compensation imaging method, an outward-facing circular aperture radar space-varying phase compensation imaging device, and a computer-readable storage medium. Background Technology

[0002] Current synthetic aperture radar imaging technology focuses on the target by slant-range projection onto a plane. However, due to spatially varying phase errors caused by height in the imaging space, the distance migration of each sampling point cannot be properly compensated, resulting in decreased imaging accuracy or even defocusing, which in turn affects the imaging quality. Summary of the Invention

[0003] This disclosure aims to provide an outward-facing circular aperture radar spatial-variable phase compensation imaging method, an outward-facing circular aperture radar spatial-variable phase compensation imaging device, and a computer-readable storage medium. It uses a digital elevation model to compensate for errors caused by spatial-variable phase, thereby solving the problem of decreased imaging accuracy caused by spatial-variable phase due to altitude.

[0004] According to one of the solutions disclosed herein, an outward-facing circular aperture radar space-varying phase compensation imaging method is provided, comprising:

[0005] Based on the different heights of the target area, the digital elevation model is divided into several imaging spaces with different heights;

[0006] After compensating for the height of the imaging space in different imaging spaces, coherent superposition is performed to obtain radar images.

[0007] In some embodiments, dividing the digital elevation model into several imaging spaces with different heights according to the different heights of the target area includes:

[0008] Spatial division of spatially variable phase imaging.

[0009] In some embodiments, the spatial division of the spatially variable phase imaging includes:

[0010] Convert the rectangular coordinate form of the digital elevation model;

[0011] Based on the comparison between the horizontal angle between the line connecting the target point and the imaging center and the threshold, a choice is made whether to perform phase compensation on the converted digital elevation model.

[0012] In some embodiments, the spatial division of the spatially variable phase imaging further includes:

[0013] Based on the transformed polar coordinate form of the digital elevation model, the imaging space is divided into several imaging spaces according to height, taking into account at least the maximum value in the digital elevation model and the horizontal angle between the target point and the imaging center.

[0014] In some embodiments, the step of coherently superimposing radar images after compensating for the height of different imaging spaces to obtain a radar image includes:

[0015] Spatial phase compensation is performed based on the preprocessed original echo signal.

[0016] In some embodiments, the preprocessing includes:

[0017] The original echo signal is compressed in the range direction.

[0018] According to one of the solutions disclosed herein, an outward-facing circular aperture radar space-varying phase-compensated imaging device is provided, comprising:

[0019] The partitioning module is configured to divide the digital elevation model into several imaging spaces with different heights based on the different heights of the target area.

[0020] The imaging module is configured to coherently superimpose images from different imaging spaces after compensation based on the height of the imaging space to obtain radar images.

[0021] In some embodiments, the partitioning module is further configured to:

[0022] Spatial division of spatially variable phase imaging.

[0023] In some embodiments, the imaging module is further configured to:

[0024] Spatial phase compensation is performed based on the preprocessed original echo signal.

[0025] According to one of the solutions of this disclosure, a computer-readable storage medium is provided, having stored thereon computer-executable instructions, which, when executed by a processor, implement:

[0026] Based on the above-mentioned outward-facing circular aperture radar spatially variable phase compensation imaging method.

[0027] The various embodiments of the outward-facing circular aperture radar (DAP) space-varying phase compensation imaging method, device, and computer-readable storage medium disclosed herein divide a digital elevation model (DEM) into several imaging spaces with different heights, based at least on the different heights of the target area. After compensating for the height of each imaging space in different imaging spaces, the DEM is coherently superimposed to obtain a radar image. This aims to compensate for errors caused by space-varying phase using a DEM, primarily addressing the problem of decreased imaging accuracy due to height-dependent space-varying phase. The embodiments of this disclosure divide the imaging space using a DEM, dividing it into several imaging spaces with different heights based on the different heights of the target area. After compensating for the height of each imaging space in different imaging spaces, the DEM is coherently superimposed to obtain a radar image. This disclosure compensates for errors caused by space-varying phase, improving radar imaging accuracy and quality.

[0028] It should be understood that the foregoing general description and the following detailed description are exemplary and illustrative only, and are not intended to limit the scope of this disclosure. Attached Figure Description

[0029] In drawings that are not necessarily drawn to scale, similar reference numerals in different views may indicate similar components. Similar reference numerals with letter suffixes or similar reference numerals with different letter suffixes may indicate different instances of similar components. The drawings are generally used to illustrate various embodiments by way of example rather than limitation, and are used together with the specification and claims to explain the disclosed embodiments.

[0030] Figure 1 A flowchart of an outward-facing circular aperture radar space-varying phase compensation imaging method according to an embodiment of the present disclosure is shown;

[0031] Figure 2 A geometric model diagram of an embodiment of this disclosure is shown;

[0032] Figure 3 The uncompensated imaging results are shown;

[0033] Figure 4 The compensated imaging results are shown;

[0034] Figure 5 A schematic diagram of an outward-facing circular aperture radar space-varying phase compensation imaging apparatus according to an embodiment of the present disclosure is shown. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0036] Synthetic Aperture Radar (SAR) is an active microwave remote sensing radar that utilizes range-direction pulse compression and azimuth-direction Doppler effects for imaging. Circular Aperture Radar (CAP) antennas move along an arc-shaped track. Through the circular motion of its platform, ground-based CAP radar can achieve 360-degree omnidirectional observation of the target, acquiring more scattering information from the target. This not only effectively improves the radar system's field of view but also achieves higher image resolution. With these advantages, ground-based CAP radar has significant importance and promising applications in high-precision ground deformation monitoring.

[0037] Current circular aperture radar (CAP) processing methods do not consider errors caused by spatial phase variation. However, the imaging accuracy of traditional ground-based CAP radar is affected by terrain undulations. If there is a height difference between the target in the scene and the imaging plane, spatial phase variation errors will be introduced into the imaging results, leading to a decrease in imaging accuracy.

[0038] In conjunction with the preceding background section, this disclosure provides illustrative examples of solutions to address the deficiencies in the prior art, but these are not intended to limit the scope of patent protection claimed in this disclosure.

[0039] As one of the solutions, such as Figure 1 As shown, embodiments of this disclosure provide an outward-facing circular aperture radar space-varying phase compensation imaging method, including:

[0040] Based on the different heights of the target area, the digital elevation model is divided into several imaging spaces with different heights;

[0041] After compensating for the height of the imaging space in different imaging spaces, coherent superposition is performed to obtain radar images.

[0042] In response to the questions raised above, and in combination with Figure 3 The uncompensated imaging results and Figure 4The images shown are the compensated imaging results. The embodiments of this disclosure aim to propose a spatially varied phase compensation method for outward-facing circular aperture radar. This method uses a digital elevation model (DEM) to compensate for errors caused by spatially varied phase, thus solving the problem of decreased imaging accuracy due to height-dependent spatially varied phase. This method divides the imaging space of the DEM into several imaging spaces with different heights based on the different heights of the target area. After compensating for the height of each imaging space, the images are coherently superimposed to obtain the radar image. The embodiments of this disclosure compensate for errors caused by spatially varied phase, improving the radar's imaging accuracy and quality.

[0043] For example, the specific imaging process can be implemented as a technical solution represented by the following steps.

[0044] In some implementations, the method of this disclosure may include: coherently superimposing radar images after compensating for the height of different imaging spaces to obtain a radar image, comprising:

[0045] Based on the preprocessed raw echo signal, spatially variable phase compensation is performed. For example, in some embodiments, the preprocessing includes: performing range compression processing on the raw echo signal.

[0046] For example, the method in this embodiment may include:

[0047] Step S1: Distance-oriented compression

[0048] S M (t, θ) = IFFT(s(t, θ))

[0049] Where s(t, θ) is the original echo signal, θ represents the azimuth angle of the antenna phase center, and t represents the echo delay.

[0050] In some implementations, the method of this disclosure embodiment may be:

[0051] The process of dividing the digital elevation model into several imaging spaces with different heights based on the different heights of the target area includes:

[0052] Spatial partitioning of the phase-varying imaging space can, for example, be implemented as including:

[0053] Convert the rectangular coordinate form of the digital elevation model;

[0054] Based on the comparison between the horizontal angle between the line connecting the target point and the imaging center and the threshold, a choice is made whether to perform phase compensation on the converted digital elevation model.

[0055] In some embodiments, the spatial division of the spatially variable phase imaging further includes:

[0056] Based on the transformed polar coordinate form of the digital elevation model, the imaging space is divided into several imaging spaces according to height, taking into account at least the maximum value in the digital elevation model and the horizontal angle between the target point and the imaging center.

[0057] For example, the method in this embodiment may further include:

[0058] Step S2: Spatial division of spatially variable phase imaging;

[0059] Step S21: Convert the rectangular coordinate form of the digital elevation model to spherical coordinate form.

[0060] V mn =(X mn Y mn Z mn ); m=1, 2,…, M; n=1, 2,…, N

[0061] In the formula, X mn Y mn It is a planar coordinate system, Z mn Yes (X) mn V mn The corresponding elevation is then determined. The Digital Elevation Model (DEM) is then transformed into polar coordinates, where M and N represent the number of pixels in the X and Y directions of the imaging grid space, respectively.

[0062]

[0063]

[0064]

[0065] The digital elevation model in polar coordinates is obtained:

[0066] V mn =(R mn A mn , Φ mn ); m=1, 2,..., M; n=1, 2,..., N

[0067] Step S22: Determination of the critical point of the spatially variable phase

[0068] like Figure 2 As shown, during the projection process, the phase between the radar imaging center and the target point P′ on the imaging plane grid is:

[0069]

[0070] The actual phase between the radar imaging center and the target point P is:

[0071]

[0072] During the imaging process, the phase difference between the target point and the actual target needs to be less than [a certain value]. Right now:

[0073]

[0074] like If phase compensation is not required, then step S24 is performed on the converted digital elevation model;

[0075] like If phase compensation is required, then step S25 is performed on the converted digital elevation model;

[0076] α is the horizontal angle between the line connecting the target point and the imaging center, and R is the horizontal angle between the target point and the line connecting the target point and the imaging center. OP Let θ be the distance from the target point to the imaging center, λ be the beamwidth, λ be the wavelength corresponding to the carrier frequency, and r be the wavelength. b This represents the radar radius.

[0077] Step S23: Divide the imaging space:

[0078] The imaging space is divided into S m segments according to height. s *n s Imaging space

[0079] V mn (s)=(R mn (s), A mn (s), Φ mn (s)), s=1,2,...,S

[0080] In the formula, (Z mn ) max This is the maximum value in the digital elevation model. ceil is used to round to +∞.

[0081] Step S24: Space without phase compensation

[0082] when hour

[0083] Φ mn (s)=0;s=1

[0084] Step S25: Space requiring phase compensation

[0085] when And when s≥2

[0086]

[0087] Step S3: Spatial Phase Compensation

[0088] Step S31: Let k = 1

[0089] Step S32: Radar position at time k

[0090] P x (k)=rcos[θ0+V θ *t s (k)]

[0091] P y (k)=rsin[θ0+V θ *t s (k)]

[0092] In the formula: r is the radar radius, θ0 is the position vector of the radar platform at time zero, and V θ Let t be the rotational speed of the radar platform. s Let k be a slow time vector, k = 1, 2, ..., na, where na is the number of azimuth points in the radar echo.

[0093] Step S33: Let s = 1

[0094] Step S34: Calculate any pixel P(m) on the imaging space grid of the radar and s at time k. s n s distance

[0095]

[0096] Step S35: s = s + 1. When s ≤ S, repeat step S34. When s > S, execute step S36.

[0097] Step S36: Calculate pixel P(m) at time k. s n s The reflected echo is at a position in the upward direction.

[0098]

[0099] In the formula, R = R P (k, m, n, s), where c is the speed of light, B r The signal bandwidth is represented by `round(·)`, which rounds the signal to the nearest integer.

[0100] Step S37: Calculate pixel P(m) at time k. s n s Projection results

[0101] In step S1, S M The k-th and id-th rows of (t, θ) are denoted as S. kidLet k = 1, 2, ..., na. na is the azimuth point number in the radar echo. id is the position of the echo reflected from pixel P at time k in the range.

[0102]

[0103] In the formula R P (k, m, n, s) represents the distance between the radar center and pixel P, and λ represents the radar transmission wavelength.

[0104] Step S38: k = k + 1. When k ≤ na, repeat steps S32 to S38. When k > na, execute step S39.

[0105] Step S39: Calculate the projection result

[0106]

[0107] All I obtained in step S37 m，n (k) is accumulated to obtain the imaging result.

[0108] As one of the solutions, such as Figure 5 As shown, embodiments of this disclosure provide an outward-facing circular aperture radar space-varying phase-compensated imaging device, comprising:

[0109] The partitioning module is configured to divide the digital elevation model into several imaging spaces with different heights based on the different heights of the target area.

[0110] The imaging module is configured to coherently superimpose images from different imaging spaces after compensation based on the height of the imaging space to obtain radar images.

[0111] As one implementation, the outward-facing circular aperture radar space-varying phase-compensated imaging device of this disclosure can be further configured, in conjunction with the steps described above, including the partitioning module, as follows:

[0112] Spatial division of spatially variable phase imaging.

[0113] As one implementation, the outward-facing circular aperture radar space-varying phase-compensated imaging device of this disclosure can be further configured, in conjunction with the steps described above, as follows:

[0114] Spatial phase compensation is performed based on the preprocessed original echo signal.

[0115] For example, the modules and sub-modules of the outward-facing circular aperture radar space-varying phase compensation imaging device in this embodiment can be further configured to implement the following steps:

[0116] Step S1: Distance-oriented compression

[0117] S M (t, θ) = IFFT(s(t, θ))

[0118] Where s(t, θ) is the original echo signal, θ represents the azimuth angle of the antenna phase center, and t represents the echo delay.

[0119] Step S2: Spatial division of space-varying phase imaging

[0120] Step S21: Convert the rectangular coordinate form of the digital elevation model to the spherical coordinate form V mn =(X mn Y mn Z mn ); m=1, 2,…, M; n=1, 2,…, N

[0121] In the formula, X mn Y mn It is a planar coordinate system, Z mn Yes (X) mn Y mn The corresponding elevation is then determined. The DEM is then transformed into polar coordinates, where M and N represent the number of pixels in the X and Y directions of the imaging grid space, respectively.

[0122]

[0123]

[0124]

[0125] The digital elevation model in polar coordinates is obtained:

[0126] V mn =(R mn A mn , Φ mn ); m=1, 2,..., M; n=1, 2,..., N

[0127] Step S22: Determination of the critical point of the spatially variable phase

[0128] like Figure 2 As shown, during the projection process, the phase between the radar imaging center and the target point P′ on the imaging plane grid is:

[0129]

[0130] The actual phase between the radar imaging center and the target point P is:

[0131]

[0132] During the imaging process, the phase difference between the target point and the actual target needs to be less than [a certain value]. Right now:

[0133]

[0134] like If phase compensation is not required, then step S24 is performed on the converted digital elevation model;

[0135] If phase compensation is required, then step S25 is performed on the converted digital elevation model, where α is the horizontal angle between the target point and the imaging center, and R... OP Let θ be the distance from the target point to the imaging center, λ be the beamwidth, λ be the wavelength corresponding to the carrier frequency, and r be the wavelength. b This represents the radar radius.

[0136] Step S23: Divide the imaging space:

[0137] The imaging space is divided into S m segments according to height. s *n s Imaging space

[0138] V mn (s)=(R mn (s), A mn (s), Φ mn (s)), s=1,2,...,S

[0139] In the formula, (Z mn ) max This is the maximum value in the digital elevation model. ceil is used to round to +∞.

[0140] Step S24: Space without phase compensation

[0141] when hour

[0142] Φ mn (s)=0;s=1

[0143] Step S25: Space requiring phase compensation

[0144] when And when s≥2

[0145]

[0146] Step S3: Spatial Phase Compensation

[0147] Step S31: Let k = 1

[0148] Step S32: Radar position at time k

[0149] P x (k)=rcos[θ0+V θ *t s (k)]

[0150] P y (k)=rsin[θ0+V θ *t s (k)]

[0151] In the formula: r is the radar radius, θ0 is the position vector of the radar platform at time zero, and V θ Let t be the rotational speed of the radar platform. s Let k be a slow time vector, k = 1, 2, ..., na, where na is the number of azimuth points in the radar echo.

[0152] Step S33: Let s = 1

[0153] Step S34: Calculate any pixel P(m) on the imaging space grid of the radar and s at time k. s n s distance

[0154]

[0155] Step S35: s = s + 1. When s ≤ S, repeat step S34. When s > S, execute step S36.

[0156] Step S36: Calculate pixel P(m) at time k. s n s The reflected echo is at a position in the upward direction.

[0157]

[0158] In the formula, R = R P (k, m, n, s), where c is the speed of light, B r The signal bandwidth is represented by `round(·)`, which rounds the signal to the nearest integer.

[0159] Step S37: Calculate pixel P(m) at time k. s n s Projection results

[0160] In step S1, S M The k-th and id-th rows of (t, θ) are denoted as S. kid Let k = 1, 2, ..., na. na is the azimuth point number in the radar echo. id is the position of the echo reflected from pixel P at time k in the range.

[0161]

[0162] In the formula R P (k, m, n, s) represents the distance between the radar center and pixel P, and λ represents the radar transmission wavelength.

[0163] Step S38: k = k + 1. When k ≤ na, repeat steps S32 to S38. When k > na, execute step S39.

[0164] Step S39: Calculate the projection result

[0165]

[0166] All I obtained in step S37 m，n (k) is accumulated to obtain the imaging result.

[0167] Specifically, one of the inventive concepts of this disclosure aims to utilize the aforementioned outward-facing circular aperture radar (DAR) space-varying phase compensation imaging method, device, and computer-readable storage medium. This method primarily divides the digital elevation model (DEM) into several imaging spaces of different heights based on the varying heights of the target area. After compensating for the heights of the imaging spaces in different imaging spaces, the DEM images are coherently superimposed to obtain a radar image. This approach aims to compensate for errors caused by space-varying phase using the DEM, primarily addressing the problem of decreased imaging accuracy due to height-dependent space-varying phase. The embodiments involved in this disclosure utilize the DEM to divide the imaging space into several imaging spaces of different heights based on the varying heights of the target area. After compensating for the heights of the imaging spaces in different imaging spaces, the DEM images are coherently superimposed to obtain a radar image. This disclosure compensates for errors caused by space-varying phase, improving radar imaging accuracy and quality.

[0168] This disclosure also provides a computer-readable storage medium storing computer-executable instructions thereon. When executed by a processor, the computer-executable instructions mainly implement the above-described outward-facing circular aperture radar space-varying phase compensation imaging method, including at least:

[0169] Based on the different heights of the target area, the digital elevation model is divided into several imaging spaces with different heights;

[0170] After compensating for the height of the imaging space in different imaging spaces, coherent superposition is performed to obtain radar images.

[0171] The above embodiments are merely exemplary embodiments of this disclosure and are not intended to limit this disclosure. The scope of protection of this disclosure is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to this disclosure within its substance and scope, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of this disclosure.

Claims

1. An outward-facing circular aperture radar space-varying phase-compensated imaging method, including: Based on the different heights of the target area, the digital elevation model is divided into several imaging spaces with different heights; After compensating for the height of the imaging space in different imaging spaces, coherent superposition is performed to obtain radar images; Spatial phase compensation includes: Step 1: Let =1; Step Two: Real-time radar position In the formula: Radar radius Let be the position vector of the radar platform at time zero. The rotational speed of the radar platform, For slow time vectors, , This represents the number of azimuth points in the radar echo; Step 3: Order ; Step 4: Calculation Time radar and any pixel on the imaging space grid distance, ， 、 、 ； Step 5: ,when When, repeat step four; when Then proceed to step six; Step Six: Calculation Moment Pixel The reflected echo is at a position upwards at a distance. In the formula c is the speed of light. For signal bandwidth, This is for rounding calculations to the nearest integer. Step 7: Calculate the first... Moment Pixel The projection results; Step 8: ,when Repeat steps two through eight when... Then, proceed to step nine; Step 9: Sum all the projection results obtained in Step 7 to obtain the imaging result.

2. The method according to claim 1, wherein, The process of dividing the digital elevation model into several imaging spaces with different heights based on the different heights of the target area includes: Spatial division of spatially variable phase imaging.

3. The method according to claim 2, wherein, The spatial division of the space-varying phase imaging includes: Convert the rectangular coordinate form of the digital elevation model; Based on the comparison between the horizontal angle between the line connecting the target point and the imaging center and the threshold, a choice is made whether to perform phase compensation on the converted digital elevation model.

4. The method according to claim 3, wherein, The spatial division of the space-varying phase imaging also includes: Based on the transformed polar coordinate form of the digital elevation model, the imaging space is divided into several imaging spaces according to height, taking into account at least the maximum value in the digital elevation model and the horizontal angle between the target point and the imaging center.

5. The method according to claim 4, wherein, The process of coherently superimposing radar images after compensating for the height of different imaging spaces to obtain radar images includes: Spatial phase compensation is performed based on the preprocessed original echo signal.

6. The method according to claim 5, wherein, The preprocessing includes: The original echo signal is compressed in the range direction.

7. An outward-facing circular aperture radar space-varying phase-compensated imaging device employing the imaging method as described in any one of claims 1 to 6, comprising: The partitioning module is configured to divide the digital elevation model into several imaging spaces with different heights based on the different heights of the target area. The imaging module is configured to coherently superimpose images from different imaging spaces after compensation based on the height of the imaging space to obtain radar images.

8. The apparatus according to claim 7, wherein, The partitioning module is further configured as follows: Spatial division of spatially variable phase imaging.

9. The apparatus according to claim 8, wherein, The imaging module is further configured as follows: Spatial phase compensation is performed based on the preprocessed original echo signal.

10. A computer-readable storage medium having stored thereon computer-executable instructions, which, when executed by a processor, implement: The outward-facing circular aperture radar spatially variable phase compensation imaging method according to any one of claims 1 to 6.

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