Low signal-to-noise ratio envelope alignment algorithm for synthetic aperture radar (ISAR) imaging of sea targets

Abstract

The invention relates to the field of radar imaging technology, and discloses a low signal-to-noise ratio envelope alignment algorithm for synthetic aperture radar (ISAR) imaging of sea targets. A linear frequency modulation signal is transmitted to a sea target by a synthetic aperture radar system to determine an echo signal path; real-time echo data of an echo signal is collected based on a sub-data collection time node; a first echo signal variation coefficient is calculated according to the first real-time echo data; a second echo signal variation coefficient is calculated according to the second real-time echo data; an echo signal variation coefficient is calculated based on the first echo signal variation coefficient and the second echo signal variation coefficient; an echo signal rotation angular velocity is optimized according to the echo signal variation coefficient to obtain an optimized echo signal rotation angular velocity, and envelope alignment is performed, so that the low signal-to-noise ratio envelope alignment accuracy of sea target ISAR imaging can be ensured, real-time monitoring of sea targets can be achieved, image clarity and resolution can be effectively enhanced, and sea target ISAR imaging quality can be ensured.

Description

Technical Field

[0001] The present invention relates to the field of radar imaging technology, and in particular to a low signal-to-noise ratio envelope alignment algorithm for synthetic aperture radar (ISAR) imaging of sea targets. Background Art

[0002] Synthetic Aperture Radar (SAR) is a high-resolution imaging radar system that acquires the reflection information of the target surface by emitting and receiving pulsed electromagnetic waves. Inverse Synthetic Aperture Radar (ISAR) imaging is a high-resolution imaging technology that uses the motion of the target relative to the radar to form a synthetic observation aperture, thereby distinguishing scattering points in the Doppler dimension.

[0003] However, existing ISAR imaging methods face many challenges under low signal-to-noise ratio conditions. The performance of traditional envelope alignment algorithms is significantly reduced in low signal-to-noise ratio environments, resulting in reduced imaging quality. The prior art introduces a network model based on the spatiotemporal attention mechanism, which learns the mapping relationship from unaligned echoes to aligned echoes through offline training to improve the accuracy of envelope alignment. However, its computational complexity is high and requires a lot of computing resources and time for offline training, which in turn increases the signal accumulation time, resulting in low imaging accumulation efficiency and failure to meet the needs of real-time monitoring. Summary of the invention

[0004] In view of this, the present invention proposes a low signal-to-noise ratio envelope alignment algorithm for synthetic aperture radar ISAR imaging of sea targets, aiming to solve the problems in the current technology of insufficient envelope alignment accuracy when ensuring ISAR imaging of sea targets under low signal-to-noise ratio conditions, high computational complexity, inability to achieve real-time monitoring, and reduced quality of ISAR imaging of sea targets.

[0005] The present invention proposes a low signal-to-noise ratio envelope alignment algorithm for synthetic aperture radar (ISAR) imaging of sea targets, comprising:

[0006] transmitting a linear frequency modulation signal to a sea target through a synthetic aperture radar system, and when the sea target receives the linear frequency modulation signal, determining a path between the sea target and the synthetic aperture radar system as an echo signal path;

[0007] Presetting a plurality of data acquisition time intervals, and acquiring real-time echo data of an echo signal in an echo signal path based on sub-data acquisition time nodes in the data acquisition time intervals, wherein the real-time echo data includes first real-time echo data and second real-time echo data;

[0008] Calculating a first echo signal variation coefficient of the data acquisition time interval according to the first real-time echo data, wherein the first real-time echo data includes a signal transmission power and an echo signal attenuation degree of a synthetic aperture radar system;

[0009] Calculating a second echo signal variation coefficient of the data acquisition time interval according to the second real-time echo data, wherein the second real-time echo data includes an echo velocity of the echo signal;

[0010] Calculating the echo signal variation coefficient of the echo signal path based on the first echo signal variation coefficient and the second echo signal variation coefficient corresponding to each data acquisition time interval;

[0011] The echo signal rotation angular velocity in the echo signal path is determined, the echo signal rotation angular velocity is optimized according to the echo signal variation coefficient to obtain an optimized echo signal rotation angular velocity, and envelope alignment is performed based on the optimized echo signal rotation angular velocity.

[0012] Further, when calculating the first echo signal variation coefficient of the data acquisition time interval according to the first real-time echo data, it includes:

[0013] Calculate the echo data coefficient corresponding to each sub-data acquisition time node according to the first real-time echo data;

[0014] ;

[0015] Among them, q is the echo data coefficient corresponding to the sub-data acquisition time node, w is the signal transmission power of the synthetic aperture radar system, e1 is the weight coefficient corresponding to the signal transmission power, d is the distance between the echo signal and the sea target, u is the state characteristic quantity in the echo signal path, e2=1-u, the value range of u is [1,2], and y is the echo signal attenuation degree corresponding to the sub-data acquisition time node.

[0016] Further, when calculating the first echo signal variation coefficient of the data acquisition time interval according to the first real-time echo data, it also includes:

[0017] Extracting the echo data coefficients in each data acquisition time interval to obtain the maximum echo data coefficient and the minimum echo data coefficient corresponding to the data acquisition time interval;

[0018] Calculating a first echo signal variation coefficient of the data acquisition time interval based on the maximum echo data coefficient and the minimum echo data coefficient;

[0019] ;

[0020] Among them, r is the first echo signal variation coefficient in the data acquisition time interval, p is the number of echo data coefficients, and a i is the i-th echo data coefficient, a max is the maximum echo data coefficient, a min is the minimum echo data coefficient, For all The maximum value in .

[0021] Further, when calculating the second echo signal variation coefficient of the data acquisition time interval according to the second real-time echo data, it includes:

[0022] Calculate the second echo data coefficient corresponding to each sub-data acquisition time node according to the second real-time echo data;

[0023] ;

[0024] Among them, d is the data reference value corresponding to the sub-data acquisition time node, g is the number of echo velocities corresponding to the sub-data acquisition time node, k h is the echo velocity of the hth echo signal;

[0025] The ratio of the echo velocity corresponding to each sub-data acquisition time node to the data reference value is calculated and used as the second echo data coefficient corresponding to the sub-data acquisition time node.

[0026] Further, when calculating the second echo signal variation coefficient of the data acquisition time interval according to the second real-time echo data, it includes:

[0027] Extracting the second echo data coefficient corresponding to each sub-data acquisition time node;

[0028] extracting identical second echo data coefficients from the second echo data coefficients, and obtaining a plurality of second echo data coefficient sequences;

[0029] Counting the number of sequences before the division of the second echo data coefficient sequence;

[0030] Extracting a second echo data coefficient from all second echo data coefficient sequences respectively, and calculating the sum of the second echo data coefficients before division;

[0031] Acquire a preset second echo data coefficient, remove all second echo data coefficient sequences that are smaller than the preset second echo data coefficient, and count the number of divided sequences of the remaining second echo data coefficient sequences;

[0032] Extracting one second echo data coefficient from the remaining second echo data coefficient sequence respectively, and calculating the sum of the divided second echo data coefficients;

[0033] The second echo signal variation coefficient of the data acquisition time interval is calculated according to the number of sequences before division, the coefficient and value of the second echo data before division, the number of sequences after division and the coefficient and value of the second echo data after division.

[0034] Further, when calculating the second echo signal variation coefficient of the data acquisition time interval according to the number of sequences before division, the coefficient and value of the second echo data before division, the number of sequences after division, and the coefficient and value of the second echo data after division, it includes:

[0035] The second echo signal variation coefficient of the data acquisition time interval is calculated according to the following formula:

[0036] ;

[0037] Among them, c is the second echo signal change coefficient in the data acquisition time interval, v1 is the number of sequences before division, v2 is the number of sequences after division, v3 is the second echo data coefficient and value before division, and v4 is the second echo data coefficient and value after division.

[0038] Further, when calculating the echo signal variation coefficient of the echo signal path based on the first echo signal variation coefficient and the second echo signal variation coefficient corresponding to each data acquisition time interval, it includes:

[0039] Randomly determine a first data collection time interval and a second data collection time interval, and extract a first extraction variation coefficient and a second extraction variation coefficient corresponding to the first data collection time interval;

[0040] extracting a third extraction variation coefficient and a fourth extraction variation coefficient corresponding to the second data collection time interval;

[0041] Calculating a first coefficient of variation difference between the first extraction coefficient of variation and the third extraction coefficient of variation;

[0042] determining a first maximum echo signal variation coefficient and a first minimum echo signal variation coefficient from all first echo signal variation coefficients;

[0043] Calculating a first signal variation coefficient range difference value of the first maximum echo signal variation coefficient and the first minimum echo signal variation coefficient;

[0044] Determine a first signal variation coefficient ratio of the first variation coefficient difference and the first signal variation coefficient extreme difference;

[0045] calculating a second coefficient of variation difference between the second extraction coefficient of variation and the fourth extraction coefficient of variation;

[0046] Determine a second maximum echo signal variation coefficient and a second minimum echo signal variation coefficient from all second echo signal variation coefficients;

[0047] Calculating a second signal variation coefficient extreme difference value of the second maximum echo signal variation coefficient and the second minimum echo signal variation coefficient;

[0048] Determine a second signal variation coefficient ratio of the second variation coefficient difference and the second signal variation coefficient extreme difference;

[0049] Calculating a signal variation coefficient product value between the first signal variation coefficient ratio and the second signal variation coefficient ratio;

[0050] The echo signal variation coefficient of the echo signal path is calculated according to all signal variation coefficient product values.

[0051] Further, when calculating the echo signal variation coefficient of the echo signal path according to the signal variation coefficient product value, it includes:

[0052] Normalizing all signal variation coefficient product values ​​to obtain a signal variation coefficient product value set;

[0053] Determine a set mean value and a set variance of the signal variation coefficient product value set, and eliminate all signal variation coefficient product values ​​that are less than the set mean value and less than the set variance;

[0054] Randomly combining the remaining signal change coefficient product values ​​in the signal change coefficient product value set in pairs to obtain a plurality of signal change coefficient product value combinations;

[0055] The echo signal variation coefficient of the echo signal path is calculated according to the signal variation coefficient product value combination.

[0056] Further, when calculating the echo signal variation coefficient of the echo signal path according to the signal variation coefficient product value combination, it includes:

[0057] The echo signal variation coefficient of the echo signal path is calculated according to the following formula:

[0058] ;

[0059] Where b is the echo signal variation coefficient of the echo signal path, n is the number of signal variation coefficient product value combinations, m1 j m2 is the larger signal variation coefficient product value in the signal variation coefficient product value combination, j is the smaller signal variation coefficient product value in the signal variation coefficient product value combination, For all The minimum value in For all The maximum value in L 2 For all The variance of .

[0060] Further, when determining the echo signal rotation angular velocity in the echo signal path, optimizing the echo signal rotation angular velocity according to the echo signal variation coefficient to obtain the optimized echo signal rotation angular velocity, it includes:

[0061] Presetting a first echo signal variation coefficient and a second echo signal variation coefficient;

[0062] Presetting a first optimization factor, a second optimization factor, and a third optimization factor;

[0063] When the echo signal variation coefficient is less than the first echo signal variation coefficient, a product value of the first optimization factor and the echo signal rotation angular velocity is calculated and used as the optimized echo signal rotation angular velocity;

[0064] When the echo signal variation coefficient is greater than or equal to the first echo signal variation coefficient and less than the second echo signal variation coefficient, the product value of the second optimization factor and the echo signal rotation angular velocity is calculated and used as the optimized echo signal rotation angular velocity;

[0065] When the echo signal variation coefficient is greater than or equal to the second echo signal variation coefficient, the product value of the third optimization factor and the echo signal rotation angular velocity is calculated and used as the optimized echo signal rotation angular velocity.

[0066] Compared with the prior art, the present invention has the following beneficial effects:

[0067] A linear frequency modulation signal is emitted to the sea target through a synthetic aperture radar system to determine the echo signal path; real-time echo data of the echo signal is collected based on the sub-data collection time node; a first echo signal variation coefficient is calculated according to the first real-time echo data; a second echo signal variation coefficient is calculated according to the second real-time echo data; an echo signal variation coefficient is calculated based on the first echo signal variation coefficient and the second echo signal variation coefficient; the echo signal rotation angular velocity is optimized according to the echo signal variation coefficient to obtain the optimized echo signal rotation angular velocity, and envelope alignment is performed, which can ensure the low signal-to-noise ratio envelope alignment accuracy of sea target ISAR imaging, realize real-time monitoring of sea targets, effectively enhance image clarity and resolution, and ensure the ISAR imaging quality of sea targets. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0069] Figure 1 A schematic flow chart of a low signal-to-noise ratio envelope alignment algorithm for synthetic aperture radar (ISAR) imaging of sea targets provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0070] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features described in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0071] like Figure 1 As shown, in some embodiments of the present application, this embodiment provides a low signal-to-noise ratio envelope alignment algorithm for synthetic aperture radar ISAR imaging of sea targets, including:

[0072] S110: transmitting a linear frequency modulation signal to a sea target through a synthetic aperture radar system, and when the sea target receives the linear frequency modulation signal, determining a path between the sea target and the synthetic aperture radar system as an echo signal path;

[0073] S120: presetting a plurality of data acquisition time intervals, and acquiring real-time echo data of an echo signal in an echo signal path based on a sub-data acquisition time node in the data acquisition time interval, wherein the real-time echo data includes first real-time echo data and second real-time echo data;

[0074] In this embodiment, the data collection time interval can be set to 20, and multiple sub-data collection time nodes are set in each data collection time interval, such as the 1st second is a sub-data collection time node, the 2nd second is a sub-data collection time node, etc. The number of sub-data collection time nodes is preferably 6, and the above can also be adjusted according to actual conditions.

[0075] S130: Calculating a first echo signal variation coefficient of the data acquisition time interval according to the first real-time echo data, wherein the first real-time echo data includes a signal transmission power and an echo signal attenuation degree of a synthetic aperture radar system;

[0076] In some embodiments of the present application, when calculating the first echo signal variation coefficient of the data acquisition time interval according to the first real-time echo data, it includes:

[0077] Calculate the echo data coefficient corresponding to each sub-data acquisition time node according to the first real-time echo data;

[0078] ;

[0079] Among them, q is the echo data coefficient corresponding to the sub-data acquisition time node, w is the signal transmission power of the synthetic aperture radar system, e1 is the weight coefficient corresponding to the signal transmission power, d is the distance between the echo signal and the sea target, u is the state characteristic quantity in the echo signal path, e2=1-u, the value range of u is [1,2], and y is the echo signal attenuation degree corresponding to the sub-data acquisition time node.

[0080] The beneficial effect of the above technical solution is that the present invention can accurately calculate the echo data coefficient corresponding to the sub-data acquisition time node, thereby laying a foundation for the calculation of the first echo signal variation coefficient.

[0081] In some embodiments of the present application, when calculating the first echo signal variation coefficient of the data acquisition time interval according to the first real-time echo data, it also includes:

[0082] Extracting the echo data coefficients in each data acquisition time interval to obtain the maximum echo data coefficient and the minimum echo data coefficient corresponding to the data acquisition time interval;

[0083] Calculating a first echo signal variation coefficient of the data acquisition time interval based on the maximum echo data coefficient and the minimum echo data coefficient;

[0084] ;

[0085] Among them, r is the first echo signal variation coefficient in the data acquisition time interval, p is the number of echo data coefficients, and a i is the i-th echo data coefficient, a max is the maximum echo data coefficient, a min is the minimum echo data coefficient, For all The maximum value in .

[0086] The beneficial effect of the above technical solution is that the present invention calculates the first echo signal variation coefficient of the data acquisition time interval based on the maximum echo data coefficient and the minimum echo data coefficient, thereby ensuring the real-time calculation of the first echo signal variation coefficient and avoiding calculation errors.

[0087] S140: Calculating a second echo signal variation coefficient of the data acquisition time interval according to the second real-time echo data, wherein the second real-time echo data includes an echo velocity of the echo signal;

[0088] In some embodiments of the present application, when calculating the second echo signal variation coefficient of the data acquisition time interval according to the second real-time echo data, it includes:

[0089] Calculate the second echo data coefficient corresponding to each sub-data acquisition time node according to the second real-time echo data;

[0090] ;

[0091] Among them, d is the data reference value corresponding to the sub-data acquisition time node, g is the number of echo velocities corresponding to the sub-data acquisition time node, k h is the echo velocity of the hth echo signal;

[0092] The ratio of the echo velocity corresponding to each sub-data acquisition time node to the data reference value is calculated and used as the second echo data coefficient corresponding to the sub-data acquisition time node.

[0093] In this embodiment, a data reference value is obtained by calculation, and then a ratio of the echo velocity to the data reference value is calculated to obtain a second echo data coefficient.

[0094] The beneficial effect of the above technical solution is that the present invention further provides a calculation basis for calculating the second echo signal variation coefficient by calculating the second echo data coefficient of the sub-data acquisition time node.

[0095] In some embodiments of the present application, when calculating the second echo signal variation coefficient of the data acquisition time interval according to the second real-time echo data, it includes:

[0096] Extracting the second echo data coefficient corresponding to each sub-data acquisition time node;

[0097] extracting identical second echo data coefficients from the second echo data coefficients, and obtaining a plurality of second echo data coefficient sequences;

[0098] Counting the number of sequences before the division of the second echo data coefficient sequence;

[0099] Extracting a second echo data coefficient from all second echo data coefficient sequences respectively, and calculating the sum of the second echo data coefficients before division;

[0100] Acquire a preset second echo data coefficient, remove all second echo data coefficient sequences that are smaller than the preset second echo data coefficient, and count the number of divided sequences of the remaining second echo data coefficient sequences;

[0101] Extracting one second echo data coefficient from the remaining second echo data coefficient sequence respectively, and calculating the sum of the divided second echo data coefficients;

[0102] The second echo signal variation coefficient of the data acquisition time interval is calculated according to the number of sequences before division, the coefficient and value of the second echo data before division, the number of sequences after division and the coefficient and value of the second echo data after division.

[0103] In this embodiment, the same second echo data coefficient is extracted, and multiple second echo data coefficient sequences are obtained, such as {ΔR1, ΔR1}, {ΔR2, ΔR2, ΔR2}, {ΔR3, ΔR3}, {ΔR4, ΔR4, ΔR4}, and ΔR1<ΔR2<ΔR3<ΔR4, and the number of sequences before division is 4, and one second echo data coefficient is extracted respectively, specifically ΔR1, ΔR2, ΔR3, ΔR4, and the preset second echo data coefficient is the variance of all second echo data coefficients, such as ΔR2, then the remaining second echo data coefficient sequence is {ΔR2, ΔR2, ΔR2}, {ΔR3, ΔR3}, {ΔR4, ΔR4, ΔR4}, and one second echo data coefficient is extracted respectively, specifically ΔR2, ΔR3, ΔR4, and the number of sequences after division is 3, and the above is shown by example.

[0104] The beneficial effect of the above technical solution is: the present invention calculates the second echo signal variation coefficient of the data acquisition time interval according to the number of sequences before division, the second echo data coefficient and value before division, the number of sequences after division and the second echo data coefficient and value after division, thereby ensuring the calculation accuracy of the second echo signal variation coefficient. At the same time, the echo signal variation coefficient can also be calculated in combination with the first echo signal variation coefficient to further enhance image clarity and resolution.

[0105] In some embodiments of the present application, when calculating the second echo signal variation coefficient of the data acquisition time interval according to the number of sequences before division, the coefficient and value of the second echo data before division, the number of sequences after division, and the coefficient and value of the second echo data after division, it includes:

[0106] The second echo signal variation coefficient of the data acquisition time interval is calculated according to the following formula:

[0107] ;

[0108] Among them, c is the second echo signal change coefficient in the data acquisition time interval, v1 is the number of sequences before division, v2 is the number of sequences after division, v3 is the second echo data coefficient and value before division, and v4 is the second echo data coefficient and value after division.

[0109] S150: calculating the echo signal variation coefficient of the echo signal path based on the first echo signal variation coefficient and the second echo signal variation coefficient corresponding to each data acquisition time interval;

[0110] In some embodiments of the present application, when calculating the echo signal variation coefficient of the echo signal path based on the first echo signal variation coefficient and the second echo signal variation coefficient corresponding to each data acquisition time interval, the method includes:

[0111] Randomly determine a first data collection time interval and a second data collection time interval, and extract a first extraction variation coefficient and a second extraction variation coefficient corresponding to the first data collection time interval;

[0112] extracting a third extraction variation coefficient and a fourth extraction variation coefficient corresponding to the second data collection time interval;

[0113] Calculating a first coefficient of variation difference between the first extraction coefficient of variation and the third extraction coefficient of variation;

[0114] determining a first maximum echo signal variation coefficient and a first minimum echo signal variation coefficient from all first echo signal variation coefficients;

[0115] Calculating a first signal variation coefficient range difference value of the first maximum echo signal variation coefficient and the first minimum echo signal variation coefficient;

[0116] Determine a first signal variation coefficient ratio of the first variation coefficient difference and the first signal variation coefficient extreme difference;

[0117] calculating a second coefficient of variation difference between the second extraction coefficient of variation and the fourth extraction coefficient of variation;

[0118] Determine a second maximum echo signal variation coefficient and a second minimum echo signal variation coefficient from all second echo signal variation coefficients;

[0119] Calculating a second signal variation coefficient extreme difference value of the second maximum echo signal variation coefficient and the second minimum echo signal variation coefficient;

[0120] Determine a second signal variation coefficient ratio of the second variation coefficient difference and the second signal variation coefficient extreme difference;

[0121] Calculating a signal variation coefficient product value between the first signal variation coefficient ratio and the second signal variation coefficient ratio;

[0122] The echo signal variation coefficient of the echo signal path is calculated according to all signal variation coefficient product values.

[0123] In this embodiment, for the sake of convenience in distinction, the first echo signal change coefficient corresponding to the first data acquisition time interval is named as the first extraction change coefficient, the second echo signal change coefficient is named as the second extraction change coefficient, the first echo signal change coefficient corresponding to the second data acquisition time interval is named as the third extraction change coefficient, and the second echo signal change coefficient is named as the fourth extraction change coefficient.

[0124] In this embodiment, the remaining data acquisition time intervals are processed according to the above method to obtain multiple signal change coefficient product values.

[0125] The beneficial effect of the above technical solution is that the present invention calculates the echo signal variation coefficient of the echo signal path according to the product values ​​of all signal variation coefficients, without manual participation in the calculation, thus ensuring the calculation accuracy and avoiding one-sidedness of the calculation.

[0126] In some embodiments of the present application, when calculating the echo signal variation coefficient of the echo signal path according to the signal variation coefficient product value, it includes:

[0127] Normalizing all signal variation coefficient product values ​​to obtain a signal variation coefficient product value set;

[0128] Determine a set mean value and a set variance of the signal variation coefficient product value set, and eliminate all signal variation coefficient product values ​​that are less than the set mean value and less than the set variance;

[0129] Randomly combining the remaining signal change coefficient product values ​​in the signal change coefficient product value set in pairs to obtain a plurality of signal change coefficient product value combinations;

[0130] The echo signal variation coefficient of the echo signal path is calculated according to the signal variation coefficient product value combination.

[0131] In this embodiment, if there are separate signal change coefficient product values ​​that are not randomly combined in the signal change coefficient product value set, deletion processing is performed.

[0132] In some embodiments of the present application, when calculating the echo signal variation coefficient of the echo signal path according to the signal variation coefficient product value combination, it includes:

[0133] The echo signal variation coefficient of the echo signal path is calculated according to the following formula:

[0134] ;

[0135] Where b is the echo signal variation coefficient of the echo signal path, n is the number of signal variation coefficient product value combinations, m1 j m2 is the larger signal variation coefficient product value in the signal variation coefficient product value combination, j is the smaller signal variation coefficient product value in the signal variation coefficient product value combination, For all The minimum value in For all The maximum value in L 2 For all The variance of .

[0136] In this embodiment, the signal variation coefficient product value combination includes two signal variation coefficient product values, and therefore, it can be determined that a larger value, a smaller value, or both are equal.

[0137] S160: Determine the echo signal rotation angular velocity in the echo signal path, optimize the echo signal rotation angular velocity according to the echo signal variation coefficient to obtain an optimized echo signal rotation angular velocity, and perform envelope alignment based on the optimized echo signal rotation angular velocity.

[0138] In some embodiments of the present application, when determining the echo signal rotation angular velocity in the echo signal path, optimizing the echo signal rotation angular velocity according to the echo signal variation coefficient to obtain the optimized echo signal rotation angular velocity, the method includes:

[0139] Presetting a first echo signal variation coefficient and a second echo signal variation coefficient;

[0140] Presetting a first optimization factor, a second optimization factor, and a third optimization factor;

[0141] When the echo signal variation coefficient is less than the first echo signal variation coefficient, a product value of the first optimization factor and the echo signal rotation angular velocity is calculated and used as the optimized echo signal rotation angular velocity;

[0142] When the echo signal variation coefficient is greater than or equal to the first echo signal variation coefficient and less than the second echo signal variation coefficient, the product value of the second optimization factor and the echo signal rotation angular velocity is calculated and used as the optimized echo signal rotation angular velocity;

[0143] When the echo signal variation coefficient is greater than or equal to the second echo signal variation coefficient, the product value of the third optimization factor and the echo signal rotation angular velocity is calculated and used as the optimized echo signal rotation angular velocity.

[0144] In this embodiment, the first echo signal variation coefficient is smaller than the second echo signal variation coefficient. The first echo signal variation coefficient is preferably 2, and the second echo signal variation coefficient is preferably 5. The specific values ​​can be adjusted according to actual conditions.

[0145] In this embodiment, the first optimization factor is smaller than the second optimization factor and smaller than the third optimization factor. The first optimization factor is preferably 0.95, the second optimization factor is preferably 1.15, and the third optimization factor is preferably 1.25. The specific factors can be adjusted according to actual conditions.

[0146] In this embodiment, the optimized echo signal rotation angular velocity is obtained to achieve the envelope of the echo signal. In ISAR imaging, envelope alignment is used to eliminate the offset of the echo signal in distance caused by the translation or rotation of the target. By adjusting the echo signal according to the optimized echo signal rotation angular velocity, the echo signal can be ensured to be in the same distance unit, thereby avoiding imaging blur.

[0147] In this embodiment, a method based on sparse representation, such as weighted compressed sensing, is used to improve the accuracy and stability of envelope alignment and ensure imaging quality. First, weighted compressed sensing is used to sparsely reconstruct the received echo signal; secondly, preliminary envelope alignment is performed based on the correlation between polar coordinate images; finally, the correlation function is used for fine adjustment to ensure accurate alignment of the envelope and further improve the resolution and clarity of the ISAR image. After envelope alignment, a clear ISAR image of a sea target is reconstructed using the polar coordinate formatting method and rotation compensation technology. Finally, a high-resolution ISAR image is output to provide reliable data support for maritime target recognition and analysis.

[0148] The beneficial effect of the above technical solution is: the present invention selects the corresponding optimization factor according to the relationship between the echo signal variation coefficient, the first echo signal variation coefficient and the second echo signal variation coefficient, and optimizes the echo signal rotation angular velocity, which can ensure the envelope alignment accuracy of sea target ISAR imaging, effectively enhance image clarity and resolution, ensure the quality of sea target ISAR imaging and avoid imaging blur.

[0149] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems or computer program products. Therefore, the present application may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0150] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems) and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0151] These computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0152] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0153] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A low signal-to-noise ratio envelope alignment algorithm for synthetic aperture radar (ISAR) imaging of sea targets, characterized in that: include: transmitting a linear frequency modulation signal to a sea target through a synthetic aperture radar system, and when the sea target receives the linear frequency modulation signal, determining a path between the sea target and the synthetic aperture radar system as an echo signal path; Presetting a plurality of data acquisition time intervals, and acquiring real-time echo data of an echo signal in an echo signal path based on sub-data acquisition time nodes in the data acquisition time intervals, wherein the real-time echo data includes first real-time echo data and second real-time echo data; Calculating a first echo signal variation coefficient of the data acquisition time interval according to the first real-time echo data, wherein the first real-time echo data includes a signal transmission power and an echo signal attenuation degree of a synthetic aperture radar system; Calculating a second echo signal variation coefficient of the data acquisition time interval according to the second real-time echo data, wherein the second real-time echo data includes an echo velocity of the echo signal; Calculating the echo signal variation coefficient of the echo signal path based on the first echo signal variation coefficient and the second echo signal variation coefficient corresponding to each data acquisition time interval; The echo signal rotation angular velocity in the echo signal path is determined, the echo signal rotation angular velocity is optimized according to the echo signal variation coefficient to obtain an optimized echo signal rotation angular velocity, and envelope alignment is performed based on the optimized echo signal rotation angular velocity.

2. The low signal-to-noise ratio envelope alignment algorithm for synthetic aperture radar (ISAR) imaging of sea targets according to claim 1 is characterized in that: When calculating the first echo signal variation coefficient of the data acquisition time interval according to the first real-time echo data, it includes: Calculate the echo data coefficient corresponding to each sub-data acquisition time node according to the first real-time echo data; ； Among them, q is the echo data coefficient corresponding to the sub-data acquisition time node, w is the signal transmission power of the synthetic aperture radar system, e1 is the weight coefficient corresponding to the signal transmission power, d is the distance between the echo signal and the sea target, u is the state characteristic quantity in the echo signal path, e2=1-u, the value range of u is [1,2], and y is the echo signal attenuation degree corresponding to the sub-data acquisition time node.

3. The low signal-to-noise ratio envelope alignment algorithm for synthetic aperture radar (ISAR) imaging of sea targets according to claim 2 is characterized in that: When calculating the first echo signal variation coefficient of the data acquisition time interval according to the first real-time echo data, it also includes: Extracting the echo data coefficients in each data acquisition time interval to obtain the maximum echo data coefficient and the minimum echo data coefficient corresponding to the data acquisition time interval; Calculating a first echo signal variation coefficient of the data acquisition time interval based on the maximum echo data coefficient and the minimum echo data coefficient; ； Among them, r is the first echo signal variation coefficient in the data acquisition time interval, p is the number of echo data coefficients, and a i is the i-th echo data coefficient, a max is the maximum echo data coefficient, a min is the minimum echo data coefficient, For all The maximum value in .

4. The low signal-to-noise ratio envelope alignment algorithm for synthetic aperture radar (ISAR) imaging of sea targets according to claim 1 is characterized in that: When calculating the second echo signal variation coefficient of the data acquisition time interval according to the second real-time echo data, it includes: Calculate the second echo data coefficient corresponding to each sub-data acquisition time node according to the second real-time echo data; ； Among them, d is the data reference value corresponding to the sub-data acquisition time node, g is the number of echo velocities corresponding to the sub-data acquisition time node, k h is the echo velocity of the hth echo signal; The ratio of the echo velocity corresponding to each sub-data acquisition time node to the data reference value is calculated and used as the second echo data coefficient corresponding to the sub-data acquisition time node.

5. The low signal-to-noise ratio envelope alignment algorithm for synthetic aperture radar (ISAR) imaging of sea targets according to claim 4 is characterized in that: When calculating the second echo signal variation coefficient of the data acquisition time interval according to the second real-time echo data, it includes: Extracting the second echo data coefficient corresponding to each sub-data acquisition time node; extracting identical second echo data coefficients from the second echo data coefficients, and obtaining a plurality of second echo data coefficient sequences; Counting the number of sequences before the division of the second echo data coefficient sequence; Extracting a second echo data coefficient from all second echo data coefficient sequences respectively, and calculating the sum of the second echo data coefficients before division; Acquire a preset second echo data coefficient, remove all second echo data coefficient sequences that are smaller than the preset second echo data coefficient, and count the number of divided sequences of the remaining second echo data coefficient sequences; Extracting one second echo data coefficient from the remaining second echo data coefficient sequence respectively, and calculating the sum of the divided second echo data coefficients; The second echo signal variation coefficient of the data acquisition time interval is calculated according to the number of sequences before division, the coefficient and value of the second echo data before division, the number of sequences after division and the coefficient and value of the second echo data after division.

6. The low signal-to-noise ratio envelope alignment algorithm for synthetic aperture radar (ISAR) imaging of sea targets according to claim 5 is characterized in that: When calculating the second echo signal variation coefficient of the data acquisition time interval according to the number of sequences before division, the coefficient and value of the second echo data before division, the number of sequences after division, and the coefficient and value of the second echo data after division, it includes: The second echo signal variation coefficient of the data acquisition time interval is calculated according to the following formula: ； Among them, c is the second echo signal change coefficient in the data acquisition time interval, v1 is the number of sequences before division, v2 is the number of sequences after division, v3 is the second echo data coefficient and value before division, and v4 is the second echo data coefficient and value after division.

7. The low signal-to-noise ratio envelope alignment algorithm for synthetic aperture radar (ISAR) imaging of sea targets according to claim 1 is characterized in that: When calculating the echo signal variation coefficient of the echo signal path based on the first echo signal variation coefficient and the second echo signal variation coefficient corresponding to each data acquisition time interval, it includes: Randomly determine a first data collection time interval and a second data collection time interval, and extract a first extraction variation coefficient and a second extraction variation coefficient corresponding to the first data collection time interval; extracting a third extraction variation coefficient and a fourth extraction variation coefficient corresponding to the second data collection time interval; Calculating a first coefficient of variation difference between the first extraction coefficient of variation and the third extraction coefficient of variation; determining a first maximum echo signal variation coefficient and a first minimum echo signal variation coefficient from all first echo signal variation coefficients; Calculating a first signal variation coefficient range difference value of the first maximum echo signal variation coefficient and the first minimum echo signal variation coefficient; Determine a first signal variation coefficient ratio of the first variation coefficient difference and the first signal variation coefficient extreme difference; calculating a second coefficient of variation difference between the second extraction coefficient of variation and the fourth extraction coefficient of variation; Determine a second maximum echo signal variation coefficient and a second minimum echo signal variation coefficient from all second echo signal variation coefficients; Calculating a second signal variation coefficient extreme difference value of the second maximum echo signal variation coefficient and the second minimum echo signal variation coefficient; Determine a second signal variation coefficient ratio of the second variation coefficient difference and the second signal variation coefficient extreme difference; Calculating a signal variation coefficient product value between the first signal variation coefficient ratio and the second signal variation coefficient ratio; The echo signal variation coefficient of the echo signal path is calculated according to all signal variation coefficient product values.

8. The low signal-to-noise ratio envelope alignment algorithm for synthetic aperture radar (ISAR) imaging of sea targets according to claim 7 is characterized in that: When calculating the echo signal variation coefficient of the echo signal path according to the signal variation coefficient product value, it includes: Normalizing all signal variation coefficient product values ​​to obtain a signal variation coefficient product value set; Determine a set mean value and a set variance of the signal variation coefficient product value set, and eliminate all signal variation coefficient product values ​​that are less than the set mean value and less than the set variance; Randomly combining the remaining signal change coefficient product values ​​in the signal change coefficient product value set in pairs to obtain a plurality of signal change coefficient product value combinations; The echo signal variation coefficient of the echo signal path is calculated according to the signal variation coefficient product value combination.

9. The low signal-to-noise ratio envelope alignment algorithm for synthetic aperture radar (ISAR) imaging of sea targets according to claim 8, characterized in that: When calculating the echo signal variation coefficient of the echo signal path according to the signal variation coefficient product value combination, it includes: The echo signal variation coefficient of the echo signal path is calculated according to the following formula: ； Where b is the echo signal variation coefficient of the echo signal path, n is the number of signal variation coefficient product value combinations, m1 j m2 is the larger signal variation coefficient product value in the signal variation coefficient product value combination, j is the smaller signal variation coefficient product value in the signal variation coefficient product value combination, For all The minimum value in For all The maximum value in L 2 For all The variance of .

10. The low signal-to-noise ratio envelope alignment algorithm for synthetic aperture radar (ISAR) imaging of sea targets according to claim 1, characterized in that: When determining the echo signal rotation angular velocity in the echo signal path, optimizing the echo signal rotation angular velocity according to the echo signal variation coefficient to obtain the optimized echo signal rotation angular velocity, the method comprises: Presetting a first echo signal variation coefficient and a second echo signal variation coefficient; Presetting a first optimization factor, a second optimization factor, and a third optimization factor; When the echo signal variation coefficient is less than the first echo signal variation coefficient, a product value of the first optimization factor and the echo signal rotation angular velocity is calculated and used as the optimized echo signal rotation angular velocity; When the echo signal variation coefficient is greater than or equal to the first echo signal variation coefficient and less than the second echo signal variation coefficient, the product value of the second optimization factor and the echo signal rotation angular velocity is calculated and used as the optimized echo signal rotation angular velocity; When the echo signal variation coefficient is greater than or equal to the second echo signal variation coefficient, the product value of the third optimization factor and the echo signal rotation angular velocity is calculated and used as the optimized echo signal rotation angular velocity.

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