Radar phase unwrapping method and system

Abstract

The invention discloses a radar phase unwrapping method and system, and belongs to the technical field of radars, and the method comprises the steps: carrying out the SAR focusing of a pre-collected data set, and obtaining a single-view complex SLC image; segmenting the single-view complex SLC image to generate a sub-band image; generating dual-frequency data through the sub-band image, and obtaining dual-frequency displacement through the dual-frequency data; performing interference processing on the single-vision complex SLC image to obtain single-frequency displacement; and solving the integer ambiguity of the single-frequency displacement through the double-frequency displacement to complete phase unwrapping. According to the method, reliable phase unwrapping and accurate displacement of the target in a larger range can be obtained under the condition that the hardware complexity and the size are not increased.

Description

Technical Field

[0001] The present invention relates to the field of radar technology, and in particular to a radar phase unwrapping method and system. Background Art

[0002] Synthetic aperture radar (SAR) is an important measurement device widely used in deformation monitoring of targets such as buildings and bridges, as well as in disaster prevention monitoring for slopes and dams. Radar interferometry often encounters problems such as phase jumps and phase unwrapping. According to the principle of radar interferometry, if the target displacement exceeds a quarter wavelength between two measurements, phase ambiguity may occur, making it impossible to accurately determine the target's displacement. While using electromagnetic waves with longer wavelengths would obviously improve this problem, the drawback is that the radar becomes larger, making implementation more difficult, and its accuracy is reduced, making it unsuitable for use in disaster prevention and mitigation. Implementing a dual-frequency radar in hardware can also address this issue, but this also significantly increases complexity and cost. Therefore, a method is needed that achieves both high spatial resolution and reliable phase unwrapping without increasing hardware complexity and keeping the size down. Summary of the Invention

[0003] The present invention aims to provide a radar phase unwrapping method and system. This method segments a focused complex image to generate dual-frequency radar data, which is then used to unwrap the original single-frequency radar data, thereby correcting the phase ambiguity in the original single-frequency data. This method achieves reliable phase unwrapping and precise target displacement over a wider range without increasing hardware complexity or size. This invention is achieved through the following technical solutions.

[0004] In a first aspect, the present invention provides a radar phase unwrapping method, comprising:

[0005] Pre-collected datasets Perform synthetic aperture radar (SAR) focusing to obtain a single-view complex (SLC) image;

[0006] The single-view complex SLC image Segmentation is performed to generate sub-band images; where i is the acquisition sequence number, ranging from 1 to n, and n is the total number of acquisition points;

[0007] Generate dual-frequency data using the sub-band images , through the dual-frequency data Get dual-frequency displacement ;

[0008] The single-view complex SLC image Perform interference processing to obtain single-frequency displacement ;

[0009] Through the dual-frequency displacement Solve the single frequency shift The whole cycle ambiguity is resolved and phase unwrapping is completed.

[0010] In practical applications, some radar data lacks the original ADC (analog-to-digital converter) data, providing only focused complex images. For example, most spaceborne SAR (SAR) systems only provide focused images. Existing data segmentation methods cannot generate dual-frequency data in these cases. The method described in this paper processes the complex images, splitting the radar data into multiple components and combining them to generate dual-frequency radar data. The dual-frequency radar corrects the phase ambiguity in the original single-frequency scan data, achieving high spatial resolution and reliable phase unwrapping without increasing hardware complexity or size, enabling accurate target displacement over a wider range. Furthermore, the method described in this paper does not require complex data processing, making it easy to implement.

[0011] Optionally, the dataset It is a single-frequency radar, and the parameters of the single-frequency radar include the single-frequency equivalent frequency and single-frequency equivalent wavelength , the expressions are as follows:

[0012] ,

[0013] ,

[0014] Where, is the starting frequency of the single-frequency radar, B is the bandwidth of the single-frequency radar, and c is the speed of light.

[0015] The dataset is the two-dimensional original data matrix of range × azimuth. Synthetic aperture radar (SAR) focusing includes range compression and azimuth focusing. The single-look complex SLC image is a two-dimensional complex matrix.

[0016] Optionally, the single-view complex SLC image Perform segmentation to generate sub-band images, including:

[0017] For single-view complex SLC images Perform a two-dimensional inverse Fourier transform to obtain the image after the two-dimensional inverse Fourier transform.

[0018] The second dimension of the image after the two-dimensional inverse Fourier transform is segmented to obtain two sub-band arrays.

[0019] Perform zero-filled Fourier transform on the two sub-band arrays to generate sub-band images.

[0020] The sub-band image includes a first sub-band image and the second sub-band image .

[0021] The size of the padded image is the same as the size of the image after the 2D inverse Fourier transform.

[0022] Optionally, the dual-frequency equivalent wavelength of the sub-band image Calculated by the following formula:

[0023] .

[0024] Optionally, dual-frequency data is generated by the sub-band image , the dual-frequency data Calculated by the following formula:

[0025] ,

[0026] Where, is the first sub-band image The absolute value of .

[0027] Dual-frequency data It is a complex array that can be used to easily extract the phase and amplitude of dual-frequency data.

[0028] Optionally, through the dual-frequency data Get dual-frequency displacement , including through the dual-frequency data Get the dual-frequency phase difference , and then through the dual-frequency phase difference Get the dual-frequency displacement .

[0029] Optionally, the dual-frequency displacement Calculated by the following formula:

[0030] ,

[0031] Where, is the dual-frequency phase difference.

[0032] The dual-frequency phase difference Calculated by the following formula:

[0033] ,

[0034] Where, Indicates the calculation of the phase angle, and conj indicates the calculation of the conjugate complex number of the complex number.

[0035] Optionally, the single frequency displacement Calculated by the following formula:

[0036] ,

[0037] Where, is the single-frequency phase difference, which is calculated using the following formula:

[0038] .

[0039] Optionally, by the dual frequency displacement Solve the single frequency shift The integer ambiguity of , including the comparison shift, is as follows:

[0040] , ,

[0041] Otherwise, it means the single frequency measurement result is single frequency displacement If ambiguity occurs, ,

[0042] Where, is the precise displacement, and N is the integer ambiguity.

[0043] Since the original single-frequency differential interferometry has high accuracy but is prone to ambiguity, while the dual-frequency differential interferometry has reduced accuracy but is not prone to ambiguity, combining the two can enhance the ability to resist ambiguity while ensuring accuracy.

[0044] The integer ambiguity N is calculated by the following formula:

[0045] ,

[0046] In the formula, int means taking an integer.

[0047] In a second aspect, the present invention provides a radar phase unwrapping system, comprising: Focus module: pre-collected datasets Perform synthetic aperture radar (SAR) focusing to obtain a single-view complex (SLC) image; Segmentation module: for the single-view complex SLC image Segmentation is performed to generate sub-band images; where i is the acquisition sequence number, ranging from 1 to n, and n is the total number of acquisition points; Dual-frequency module: Generates dual-frequency data through the sub-band image , through the dual-frequency data Get dual-frequency displacement ; Interference module: the single-view complex SLC image Perform interference processing to obtain single-frequency displacement ; Unwrapping module: through the dual-frequency displacement Solve the single frequency shift The whole cycle ambiguity is resolved and phase unwrapping is completed.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] The radar phase unwrapping method introduced in this invention, when raw radar data obtained through an analog-to-digital converter (A / D converter) is unavailable and only single-view complex (SLC) images are available, can be directly processed to extract dual-frequency data from the SLC images. This dual-frequency data is then used to resolve the integer ambiguity of the single-frequency data, completing phase unwrapping. This method reduces errors caused by phase ambiguity and improves the accuracy of radar monitoring of target displacement without increasing hardware complexity or reducing hardware size. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Shown is a schematic flow chart of the radar phase unwrapping method of the present invention. DETAILED DESCRIPTION

[0051] The following is a further description with reference to the accompanying drawings and specific embodiments. It should be understood that in the description of the present invention, the terms "first," "second," etc. are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Therefore, a feature designated "first," "second," etc. may explicitly or implicitly include one or more of the features.

[0052] Example 1 This embodiment introduces a radar phase unwrapping method, including the following contents:

[0053] Pre-collected datasets Perform synthetic aperture radar (SAR) focusing to obtain a single-view complex (SLC) image;

[0054] The single-view complex SLC image Segmentation is performed to generate sub-band images; where i is the acquisition sequence number, ranging from 1 to n, and n is the total number of acquisition points;

[0055] Generate dual-frequency data using the sub-band images , through the dual-frequency data Get dual-frequency displacement ;

[0056] The single-view complex SLC image Perform interference processing to obtain single-frequency displacement ;

[0057] Through the dual-frequency displacement Solve the single frequency shift The whole cycle ambiguity is resolved and phase unwrapping is completed.

[0058] In practical applications, some radar data lacks the original ADC (analog-to-digital converter) data, providing only focused complex images. For example, most spaceborne SAR (SAR) systems only provide focused images. Existing data segmentation methods cannot generate dual-frequency data in these cases. The method described in this paper processes the complex images, splitting the radar data into multiple components and combining them to generate dual-frequency radar data. The dual-frequency radar corrects the phase ambiguity in the original single-frequency scan data, achieving high spatial resolution and reliable phase unwrapping without increasing hardware complexity or size, enabling accurate target displacement over a wider range. Furthermore, the method described in this paper does not require complex data processing, making it easy to implement.

[0059] Example 2 Based on Example 1, this example introduces a specific implementation process of a radar phase unwrapping method, such as Figure 1 As shown, specifically including the following:

[0060] In a specific implementation of the embodiment of the present invention, the data set It is a single-frequency radar. The parameters of single-frequency radar include single-frequency equivalent frequency and single-frequency equivalent wavelength , the expressions are as follows:

[0061] ,

[0062] ,

[0063] Where, is the starting frequency of the single-frequency radar, B is the bandwidth of the single-frequency radar, and c is the speed of light.

[0064] Among them, the dataset is the two-dimensional original data matrix of range × azimuth. Synthetic aperture radar (SAR) focusing includes range compression and azimuth focusing. The single-look complex SLC image is a two-dimensional complex matrix.

[0065] In a specific implementation of the embodiment of the present invention, the single-view complex SLC image Perform segmentation to generate sub-band images, including:

[0066] For single-view complex SLC images Perform a two-dimensional inverse Fourier transform to obtain the image after the two-dimensional inverse Fourier transform.

[0067] The second dimension of the image after the two-dimensional inverse Fourier transform is segmented to obtain two sub-band arrays.

[0068] Perform zero-filled Fourier transform on the two sub-band arrays to generate sub-band images.

[0069] The sub-band image includes a first sub-band image and the second sub-band image .

[0070] The size of the padded image is the same as the image after the 2D inverse Fourier transform.

[0071] In a specific implementation of the embodiment of the present invention, the dual-frequency equivalent wavelength of the sub-band image Calculated by the following formula:

[0072] .

[0073] In a specific implementation of the embodiment of the present invention, dual-frequency data is generated by sub-band images. , dual-frequency data Calculated by the following formula:

[0074] ,

[0075] Where, is the first sub-band image The absolute value of .

[0076] Dual-frequency data It is a complex array that can be used to easily extract the phase and amplitude of dual-frequency data.

[0077] In a specific implementation of the embodiment of the present invention, dual-frequency data Get dual-frequency displacement , including through dual-frequency data Get the dual-frequency phase difference , and then through the dual-frequency phase difference Get dual-frequency displacement .

[0078] In a specific implementation of the embodiment of the present invention, dual frequency shift Calculated by the following formula:

[0079] , where is the dual-frequency phase difference.

[0080] Dual-frequency phase difference Calculated by the following formula:

[0081] , where Indicates the calculation of the phase angle, and conj indicates the calculation of the conjugate complex number of the complex number.

[0082] Single frequency displacement Calculated by the following formula:

[0083] ,

[0084] Where, is the single-frequency phase difference, which is calculated using the following formula:

[0085] .

[0086] In a specific implementation of the embodiment of the present invention, by dual frequency shift Single frequency shift solution The integer ambiguity of , including the comparison shift, is as follows:

[0087] , ,

[0088] Otherwise, it means the single frequency measurement result is single frequency displacement If ambiguity occurs, ,

[0089] Where, is the precise displacement, and N is the integer ambiguity.

[0090] Since the original single-frequency differential interferometry has high accuracy but is prone to ambiguity, while the dual-frequency differential interferometry has reduced accuracy but is not prone to ambiguity, combining the two can enhance the ability to resist ambiguity while ensuring accuracy.

[0091] In a specific implementation of the embodiment of the present invention, the integer ambiguity N is calculated using the following formula:

[0092] ,

[0093] In the formula, int means integer.

[0094] In a specific implementation of the embodiment of the present invention, taking actual parameters as an example, the actual displacement measurements of two targets, 1 mm and 20 mm, are verified. The basic parameters are as follows:

[0095] Starting frequency: ,

[0096] bandwidth: ,

[0097] ADC sampling rate: ,

[0098] Scan time: ,

[0099] Number of samples: ,

[0100] Target:

[0101] Target 1: displacement ,

[0102] Target 2: displacement ,

[0103] Speed of light: ,

[0104] The measurement error of the radar is 0.02 radians.

[0105] The procedure is as follows:

[0106] 1. Data acquisition

[0107] Acquire raw data , number of samples .

[0108] Single-frequency parameters:

[0109] Equivalent frequency: ,

[0110] Equivalent wavelength: .

[0111] 2. SAR focusing

[0112] Focus , generate single-look complex (SLC) image ,

[0113] Range resolution (full bandwidth): .

[0114] 3. Data segmentation (non-overlapping equal division)

[0115] Fourier transform to the frequency domain, segmented into first sub-band image and second sub-band image :

[0116] Dual-frequency equivalent wavelength of sub-band image: .

[0117] 4. Multi-epoch observation

[0118] Two observations, target displacement occurs:

[0119] Goal 1: ,

[0120] Goal 2: .

[0121] 5. Dual-frequency data generation and phase difference calculation:

[0122] ,

[0123] .

[0124] 6. Interference processing

[0125] Single frequency equivalent wavelength ( ):

[0126] Phase change (two-way displacement ):

[0127] ,

[0128] Where d is the actual displacement measurement or .

[0129] The formula for calculating the phase difference introduced above in this embodiment is to calculate the phase difference and displacement based on the measured values. Here, the phase difference is calculated based on the actual displacement to verify the correctness of the above formula.

[0130] Target 1 ( ):

[0131] ,

[0132] Add error, ,

[0133] ,

[0134] Target 2 ( :

[0135] ,

[0136] mold :

[0137] ,

[0138] Adding noise error: ,

[0139] .

[0140] Dual-frequency equivalent wavelength of sub-band image ( ):

[0141] Goal 1: ,

[0142] Adding noise error: ,

[0143] ,

[0144] Goal 2: ,

[0145] Adding noise error: ,

[0146] .

[0147] The following is a comprehensive solution:

[0148] 7. Phase unwrapping and displacement calculation

[0149] Goal 1:

[0150] Compare:

[0151] ,

[0152] because ,therefore is the precise displacement of target 1,

[0153] So in the absence of ambiguity: ;

[0154] Goal 2:

[0155] Compare:

[0156] ,

[0157] because Therefore, the single-frequency measurement result of target 2 contains ambiguity, and it is necessary to further resolve the ambiguity to obtain the precise displacement of target 2.

[0158] Blur: ,

[0159] Precise displacement: ,

[0160] At this point, the precise displacements of the two targets are accurately obtained.

[0161] Example 3 This embodiment provides a radar phase unwrapping system, including: Focus module: pre-collected datasets Perform synthetic aperture radar (SAR) focusing to obtain a single-view complex (SLC) image; Segmentation module: for the single-view complex SLC image Segmentation is performed to generate sub-band images; where i is the acquisition sequence number, ranging from 1 to n, and n is the total number of acquisition points; Dual-frequency module: Generates dual-frequency data through the sub-band image , through the dual-frequency data Get dual-frequency displacement ; Interference module: the single-view complex SLC image Perform interference processing to obtain single-frequency displacement ; Unwrapping module: through the dual-frequency displacement Solve the single frequency shift The whole cycle ambiguity is resolved and phase unwrapping is completed.

[0162] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which are all protected by the present invention.

Claims

1. A radar phase unwrapping method, characterized in that: include: Pre-collected datasets Perform synthetic aperture radar (SAR) focusing to obtain a single-view complex (SLC) image; The single-view complex SLC image Segmentation is performed to generate sub-band images; where i is the acquisition sequence number, ranging from 1 to n, and n is the total number of acquisition points; Generate dual-frequency data using the sub-band images , through the dual-frequency data Get dual-frequency displacement ; The single-view complex SLC image Perform interference processing to obtain single-frequency displacement ; Through the dual-frequency displacement Solve the single frequency shift The whole cycle ambiguity is resolved and phase unwrapping is completed.

2. The radar phase unwrapping method according to claim 1, wherein: The dataset It is a single-frequency radar, and the parameters of the single-frequency radar include the single-frequency equivalent frequency and single-frequency equivalent wavelength , the expressions are as follows: ， ， Where, is the starting frequency of the single-frequency radar, B is the bandwidth of the single-frequency radar, and c is the speed of light.

3. The radar phase unwrapping method according to claim 1, wherein: The single-view complex SLC image Perform segmentation to generate sub-band images, including: For single-view complex SLC images Perform a two-dimensional inverse Fourier transform to obtain the image after the two-dimensional inverse Fourier transform. The second dimension of the image after the two-dimensional inverse Fourier transform is segmented to obtain two sub-band arrays. Perform zero-filled Fourier transform on the two sub-band arrays to generate sub-band images. The sub-band image includes a first sub-band image and the second sub-band image .

4. The radar phase unwrapping method according to claim 3, wherein: Dual-frequency equivalent wavelength of the sub-band image Calculated by the following formula: 。 5. The radar phase unwrapping method according to claim 3, wherein: Generate dual-frequency data using the sub-band images , the dual-frequency data Calculated by the following formula: ， Where, is the first sub-band image The absolute value of .

6. The radar phase unwrapping method according to claim 4, wherein: Through the dual-frequency data Get dual-frequency displacement , including through the dual-frequency data Get the dual-frequency phase difference , and then through the dual-frequency phase difference Get the dual-frequency displacement .

7. The radar phase unwrapping method according to claim 6, wherein: The dual-frequency shift Calculated by the following formula: ， Where, is the dual-frequency phase difference, The dual-frequency phase difference Calculated by the following formula: ， Where, Indicates the calculation of the phase angle, and conj indicates the calculation of the conjugate complex number of the complex number.

8. The radar phase unwrapping method according to claim 1, wherein: The single frequency shift Calculated by the following formula: ， Where, is the single-frequency phase difference, which is calculated using the following formula: 。 9. The radar phase unwrapping method according to claim 7, wherein: Through the dual-frequency displacement Solve the single frequency shift The integer ambiguity of , including the comparison shift, is as follows: ， ， Otherwise, it means the single frequency measurement result is single frequency displacement If ambiguity occurs, , Where, is the precise displacement, N is the integer ambiguity; The integer ambiguity N is calculated by the following formula: ， In the formula, int means integer.

10. A radar phase unwrapping system, comprising: Focus module: pre-collected datasets Perform synthetic aperture radar (SAR) focusing to obtain a single-view complex (SLC) image; Segmentation module: for the single-view complex SLC image Segmentation is performed to generate sub-band images; where i is the acquisition sequence number, ranging from 1 to n, and n is the total number of acquisition points; Dual-frequency module: Generates dual-frequency data through the sub-band image , through the dual-frequency data Get dual-frequency displacement ; Interference module: the single-view complex SLC image Perform interference processing to obtain single-frequency displacement ; Unwrapping module: through the dual-frequency displacement Solve the single frequency shift The whole cycle ambiguity is resolved and phase unwrapping is completed.

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