Linear array passive synthetic aperture method, device, equipment and readable storage medium

Abstract

The present application provides a linear array passive synthetic aperture method, apparatus, device, and readable storage medium. The method includes: dividing the i-th snapshot data of the linear array into an upper array and a lower array, performing beamforming at a target azimuth angle and a target frequency, and obtaining an upper half array initial result and a lower half array initial result of the i-th snapshot data; calculating a phase difference of the m+1-th snapshot data based on the upper half array initial result of the m+1-th snapshot data and the lower half array initial result of the m-th snapshot data; accumulating and compensating the phase differences of the second to m+1-th snapshot data to the target initial result of the m+1-th snapshot data to obtain a compensated result of the m+1-th snapshot data; and coherently superimposing the target initial result of the first snapshot data and the compensated results of the second to M-th snapshot data to obtain a narrowband synthetic aperture azimuth spectrum of the target azimuth angle at the target frequency. Through the present application, the synthetic aperture does not require array element overlap and can adapt to multi-target scenarios.

Description

Technical Field

[0001] The present application relates to the technical field of array signal processing, and in particular to a linear array passive synthetic aperture method, apparatus, device and readable storage medium. Background Art

[0002] In the low-frequency segment (<100Hz), the main lobe of conventional beamforming algorithms is relatively wide, requiring a longer array to achieve higher azimuth resolution. Passive synthetic aperture technology, by jointly processing the signals of a moving array at different temporal and spatial positions, can form a virtual aperture that is several or even dozens of times larger than the actual physical aperture, giving full play to the temporal coherence of low-frequency signals and using time gain in exchange for spatial gain, thereby achieving higher azimuth resolution and array gain.

[0003] Currently, passive synthetic aperture algorithms are limited to methods that partially overlap the spatial dimensions of array elements. These algorithms calculate the phase difference caused by relative motion between overlapping elements and compensate for it in the signals of non-overlapping elements, ultimately achieving array expansion. Algorithms such as ETAM (Extended Towed Array Measurement) and FFTSA (Fast Fourier Transform Synthetic Aperture) place high demands on the array's posture and require the presence of overlapping elements. Research on passive synthetic aperture technology focuses on improving the accuracy of phase difference estimation for overlapping elements. Consequently, current passive synthetic aperture algorithms experience significant performance degradation when precise control of element overlap is difficult due to factors such as inaccurately known motion speeds and uncertain array motion. Summary of the Invention

[0004] The present application provides a linear array passive synthetic aperture method, apparatus, device and readable storage medium, which can solve the technical problem in the prior art that the passive synthetic aperture algorithm performance is seriously degraded when array element overlap is difficult to accurately control.

[0005] In a first aspect, an embodiment of the present application provides a linear array passive synthetic aperture method, the linear array passive synthetic aperture method comprising:

[0006] The i-th snapshot data of the linear array is divided into the upper half array and the lower half array, and beamforming is performed on the target azimuth and target frequency to obtain the initial results of the upper half array and the lower half array of the i-th snapshot data, where i is a positive integer in the range [1, M] and M is the total number of snapshots;

[0007] The phase difference of the m+1th snapshot data is calculated based on the initial result of the upper half array of the m+1th snapshot data and the initial result of the lower half array of the mth snapshot data, where m is any positive integer in the range of [1, M-1].

[0008] Accumulate and compensate the phase differences of the 2nd to (m+1th) snapshot data to the target initial result of the (m+1th) snapshot data to obtain the compensation result of the (m+1th) snapshot data, where the target initial result is the lower half array initial result or the full array initial result, and the full array initial result is composed of the upper half array initial result and the lower half array initial result;

[0009] The target initial result of the first snapshot data and the compensation results of the second to M-th snapshot data are coherently superimposed to obtain a narrowband synthetic aperture azimuth spectrum of the target azimuth angle at the target frequency.

[0010] Furthermore, in one embodiment, after the step of coherently superimposing the target initial result of the first snapshot data and the compensation results of the second to M-th snapshot data to obtain a narrowband synthetic aperture azimuth spectrum of the target azimuth angle at the target frequency, the method further includes:

[0011] The narrowband synthetic aperture azimuth spectra of the target azimuth at multiple target frequencies are incoherently superimposed to obtain the broadband synthetic aperture output azimuth spectrum of the target azimuth.

[0012] Furthermore, in one embodiment, the calculation formulas for the initial results of the first half of the i-th snapshot data and the initial results of the second half of the i-th snapshot data are:

[0013]

[0014]

[0015] in, are the initial results of the upper and lower half arrays of the i-th snapshot data, f is the target frequency, θ is the target azimuth, are the upper half frequency domain signal and the lower half frequency domain signal of the i-th snapshot data at the target frequency, are the upper half array weighted vector and the lower half array weighted vector of the target azimuth and target frequency respectively. The upper half array weighted vector and the lower half array weighted vector differ by a phase offset, which can be expressed as:

[0016]

[0017] Among them, H represents the conjugate transpose, N is the number of array elements, is the phase difference between array elements corresponding to the target azimuth angle, d is the array element spacing, and c is the speed of sound.

[0018] Furthermore, in one embodiment, the calculation formula for the compensation result of the (m+1)th snapshot data is:

[0019]

[0020] in, is the compensation result of the m+1th snapshot data, B m+1 (θ,f) is the target initial result of the m+1th snapshot data, is the phase difference of the x+1th snapshot data.

[0021] Furthermore, in one embodiment, the product of the length of the snapshot data and the total number of snapshots is smaller than the time correlation radius of the signal of the target frequency.

[0022] Furthermore, in one embodiment, the weighting method used in beamforming is conventional beamforming weighting, c, or adaptive weighting.

[0023] Furthermore, in one embodiment, the phase difference calculation method is a cross-correlation method, a multi-frequency point averaging method or a least squares method.

[0024] In a second aspect, an embodiment of the present application further provides a linear array passive synthetic aperture device, the linear array passive synthetic aperture device comprising:

[0025] A beamforming module is configured to divide the i-th snapshot data of the linear array into an upper array and a lower array, and perform beamforming on the target azimuth and target frequency to obtain an initial result of the upper array and an initial result of the lower array for the i-th snapshot data. The product of the snapshot data length and the total number of snapshots is less than the time correlation radius of the signal at the target frequency, i is a positive integer in the range [1, M], and M is the total number of snapshots.

[0026] a phase difference calculation module, configured to calculate a phase difference of the m+1th snapshot data based on an initial result of an upper half array of the m+1th snapshot data and an initial result of a lower half array of the mth snapshot data, where m is any positive integer in the range of [1, M-1];

[0027] a phase compensation module, configured to accumulate and compensate the phase differences of the second to m+1th snapshot data to a target initial result of the m+1th snapshot data to obtain a compensation result of the m+1th snapshot data, where the target initial result is a lower-half array initial result or a full-array initial result, and the full-array initial result is composed of an upper-half array initial result and a lower-half array initial result;

[0028] The coherent superposition module is used to coherently superpose the target initial result of the first snapshot data and the compensation results of the second to M-th snapshot data to obtain a narrowband synthetic aperture azimuth spectrum of the target azimuth angle at the target frequency.

[0029] In a third aspect, an embodiment of the present application further provides a linear array passive synthetic aperture device, which includes a processor, a memory, and a linear array passive synthetic aperture program stored in the memory and executable by the processor, wherein when the linear array passive synthetic aperture program is executed by the processor, the steps of the above-mentioned linear array passive synthetic aperture method are implemented.

[0030] In a fourth aspect, an embodiment of the present application further provides a readable storage medium, on which a linear array passive synthetic aperture program is stored, wherein when the linear array passive synthetic aperture program is executed by a processor, the steps of the above-mentioned linear array passive synthetic aperture method are implemented.

[0031] In this application, the snapshot data of the linear array is first divided into the upper and lower arrays for beamforming, and then the phase difference caused by the relative motion of the target and the linear array is calculated with the help of the beam domain output of the lower array of the former and the beam domain output of the upper array of the latter in the adjacent snapshot data. The beam domain output of each snapshot data after the first is compensated with the help of the phase difference to align it to the initial reference point and then coherently superimpose it to obtain a passive synthetic aperture output, thereby realizing array aperture expansion. Through this application, on the one hand, the beam domain output phase is compensated with the help of the symmetry of the upper and lower arrays of the linear array, and there is no need to predict the motion parameters to control the overlap of the array elements. On the other hand, phase difference compensation is performed based on the beam domain to suppress multi-target mutual interference, improve the signal-to-interference-noise ratio, give full play to the advantage of the spatial coherence radius of the low-frequency signal, convert the time gain into spatial gain, and obtain an azimuth spectrum with high resolution and low sidelobe effect, which is suitable for multi-target and far-field conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a flow chart of a linear array passive synthetic aperture method according to an embodiment of the present application;

[0033] Figure 2 Schematic diagram of the azimuth spectrum of dual-target single-frequency signals processed by this application and the prior art;

[0034] Figure 3 Schematic diagram of the azimuth spectrum of dual-target broadband LFM signals processed by this application and the prior art;

[0035] Figure 4 This is a schematic diagram of the functional modules of a linear array passive synthetic aperture device in one embodiment of the present application;

[0036] Figure 5 This is a schematic diagram of the hardware structure of the linear array passive synthetic aperture device involved in the embodiment of the present application. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0038] In order to make the objectives, technical solutions and advantages of this application clearer, the implementation methods of this application will be further described in detail below with reference to the accompanying drawings.

[0039] In a first aspect, an embodiment of the present application provides a linear array passive synthetic aperture method.

[0040] Figure 1 A schematic flow chart of a linear array passive synthetic aperture method in one embodiment of the present application is shown.

[0041] Reference Figure 1 In one embodiment, a linear array passive synthetic aperture method includes the following steps:

[0042] S1. Split the i-th snapshot data of the linear array into the upper and lower halves, and perform beamforming on the target azimuth and target frequency to obtain the initial results of the upper and lower halves of the i-th snapshot data, where i is a positive integer in the range [1, M] and M is the total number of snapshots.

[0043] Specifically, the linear array includes N array elements arranged in a straight line, the 1st to N / 2th array elements constitute the upper half array, the N / 2+1th to Nth array elements constitute the lower half array, and the time domain signal of the upper half array of the i-th snapshot data includes ...、 The time domain signal of the second half of the i-th snapshot data includes ...、 The upper half array time domain signal and the lower half array time domain signal are Fourier transformed to obtain the upper half array frequency domain signal and the lower half array frequency domain signal, and the target frequency part is selected from them for frequency domain beamforming.

[0044] For example, the calculation formulas for the initial results of the first half and the second half of the i-th snapshot data are:

[0045]

[0046] in, are the initial results of the upper and lower half arrays of the i-th snapshot data, f is the target frequency, θ is the target azimuth, are the upper half frequency domain signal and the lower half frequency domain signal of the i-th snapshot data at the target frequency, are the upper half array weighted vector and the lower half array weighted vector of the target azimuth and target frequency respectively. The upper half array weighted vector and the lower half array weighted vector differ by a phase offset, which can be expressed as:

[0047]

[0048] Among them, H represents the conjugate transpose, N is the number of array elements, is the phase difference between array elements corresponding to the target azimuth angle, d is the array element spacing, and c is the speed of sound.

[0049] Optionally, the weighting method adopted by the beamforming is conventional beamforming (CBF) weighting, Bartlett Null Beamforming (BNF) weighting, or adaptive weighting.

[0050] CBF weighting compensates the phase of the received signals from each array element, ensuring that the signals in the desired direction are superimposed in phase, achieving beam pointing. The CBF weighting algorithm is simple, easy to implement and understand, requires minimal computation, and has low hardware requirements. It is suitable for scenarios with high real-time requirements and relatively simple interference environments.

[0051] The principle of BNF weighting is to maximize the output power in the target direction and minimize the output power in the interference direction to 0. BNF weighting achieves interference suppression by constructing a weight vector that is orthogonal to the interference array's current vector.

[0052] Adaptive weighting adjusts the weighting coefficients in real time based on the signals received by the array to adapt to changes in the signal and interference environment. Common adaptive algorithms include the least mean square error (LMS) algorithm and the recursive least squares (RLS) algorithm. In practical applications, adaptive weighting algorithms automatically adjust the weighting coefficients based on the direction and strength of the interference signal, allowing the beam to suppress interference while maintaining gain on the target signal. Adaptive weighting has strong anti-interference capabilities, can track changes in interference signals in real time and effectively suppress them, and can maintain good performance even in complex and changing interference environments. It can automatically optimize the beam direction according to different signal environments, improving the detection and resolution capabilities of target signals.

[0053] S2. Calculate the phase difference of the (m+1)th snapshot data according to the initial result of the first half of the (m+1)th snapshot data and the initial result of the second half of the (m)th snapshot data, where m is a positive integer in the range of [1, M-1].

[0054] Specifically, the calculation formula for the phase difference of the (m+1)th snapshot data is:

[0055]

[0056] in, is the phase difference of the m+1th snapshot data, is the initial result of the second half of the m-th snapshot data, is the initial result of the upper half of the (m+1)th snapshot data, and angle() is the phase difference calculation operation.

[0057] Optionally, the phase difference calculation method is a cross-correlation method, a multi-frequency point averaging method or a least squares method.

[0058] The cross-correlation method calculates phase difference based on the correlation between signals. This method is relatively simple to calculate and has a certain degree of noise suppression. If the noise is random and uncorrelated with the signal, the noise's impact will be averaged out when calculating the cross-correlation method. The cross-correlation method is suitable for scenarios with a relatively uniform signal frequency and a high signal-to-noise ratio.

[0059] The multi-frequency averaging method is suitable for situations where the signal contains multiple frequency components. It can effectively process complex signals containing multiple frequency components. By averaging the phase differences of multiple frequency points, it can reduce the impact of noise or interference at a single frequency point on the phase difference calculation and improve the accuracy of phase difference estimation.

[0060] The least squares method calculates phase difference based on the principle of error minimization. It offers high accuracy and can accurately estimate phase difference by minimizing error in the presence of noise and interference. The least squares method is applicable to various signal types, as long as a suitable signal model can be established. It also effectively handles complex situations where both signal amplitude and phase vary simultaneously.

[0061] The phase difference between adjacent snapshots caused by motion is:

[0062]

[0063] Where T is the snapshot length and v is the dragging speed.

[0064] The adjacent snapshot half-array beam domain output can be written as follows:

[0065]

[0066] Then there is

[0067]

[0068] The adjacent snapshot full array beam domain outputs have the following relationship:

[0069]

[0070] To B m+1 (θ,f) compensation phase -φ m+1, can be realized with B m (θ,f) are in phase, and further coherent superposition of different snapshot beam domain outputs can be achieved.

[0071] S3. Accumulate and compensate the phase differences of the 2nd to (m+1th) snapshot data to the target initial result of the (m+1th) snapshot data to obtain a compensated result of the (m+1th) snapshot data, where the target initial result is the lower-half initial result or the full-half initial result, and the full-half initial result is composed of the upper-half initial result and the lower-half initial result.

[0072] Specifically, the phase difference of the (m+1)th snapshot data represents the phase difference caused by the relative motion between the target and the linear array during the (m+1)th snapshot. In order to align the beam domain output of the (m+1)th snapshot data to the initial reference point, that is, the position corresponding to the linear array during the first snapshot, the phase differences of the snapshot data from the second to the (m+1)th snapshot need to be accumulated as the compensation phase.

[0073] For example, the calculation formula for the compensation result of the (m+1)th snapshot data is:

[0074]

[0075] in, is the compensation result of the m+1th snapshot data, B m+1 (θ,f) is the target initial result of the m+1th snapshot data, is the phase difference of the x+1th snapshot data.

[0076] S4. Coherently superimpose the target initial result of the first snapshot data and the compensation results of the second to M-th snapshot data to obtain a narrowband synthetic aperture azimuth spectrum of the target azimuth angle at the target frequency.

[0077] Specifically, coherent superposition refers to the operation of superimposing multiple signals with a fixed phase relationship during signal processing. The frequencies of these signals are the same and the phase difference between them remains constant.

[0078] Therefore, in this embodiment, the snapshot data of the linear array is first divided into the upper and lower arrays for beamforming, and then the phase difference caused by the relative motion of the target and the linear array is calculated with the help of the beam domain output of the lower array of the former and the beam domain output of the upper array of the latter in the adjacent snapshot data. The beam domain output of each snapshot data after the first is compensated with the help of the phase difference to align it to the initial reference point and then coherently superimpose it to obtain a passive synthetic aperture output, thereby realizing array aperture expansion. Through this application, on the one hand, the beam domain output phase is compensated with the help of the symmetry of the upper and lower arrays of the linear array, and there is no need to predict the motion parameters to control the overlap of the array elements. On the other hand, phase difference compensation is performed based on the beam domain to suppress multi-target mutual interference, improve the signal-to-interference-noise ratio, give full play to the advantage of the spatial coherence radius of the low-frequency signal, and convert the time gain into spatial gain to obtain an azimuth spectrum with high resolution and low sidelobe effect, which is suitable for multi-target and far-field conditions.

[0079] Figure 2 A schematic diagram of the azimuth spectrum of dual-target single-frequency signals processed by the present application and the prior art is shown.

[0080] Reference Figure 2 Compared with the narrow-band azimuth spectrum obtained by processing in the prior art, it can be seen that the narrow-band azimuth spectrum obtained by processing in the present application has a narrower main lobe and lower side lobes, can achieve aperture expansion, and obtain higher spatial gain and higher azimuth resolution.

[0081] Optionally, the linear array can be a towed linear array or an underwater platform side linear array. Due to its unique operating mode, towed linear arrays exhibit formation distortion, making element overlap difficult to achieve. This results in significant performance degradation when using passive synthetic aperture algorithms such as ETAM and FFTSA, which have high requirements for formation posture. However, the algorithm in this application offers significant performance advantages.

[0082] Furthermore, in one embodiment, after the step of coherently superimposing the target initial result of the first snapshot data and the compensation results of the second to M-th snapshot data to obtain a narrowband synthetic aperture azimuth spectrum of the target azimuth angle at the target frequency, the method further includes:

[0083] The narrowband synthetic aperture azimuth spectra of the target azimuth at multiple target frequencies are incoherently superimposed to obtain the broadband synthetic aperture output azimuth spectrum of the target azimuth.

[0084] Specifically, incoherent superposition refers to the process of superimposing multiple signals that have no fixed phase relationship or whose phase relationships vary randomly during signal processing. In incoherent superposition, due to the uncertainty of the phase relationship, the amplitude of the superimposed signals cannot be controlled by phase difference, as in coherent superposition.

[0085] In this embodiment, due to the randomness of color noise, the performance of the present application may be unstable when applied to narrowband. However, when applied to broadband, relatively stable high-resolution performance can be obtained by superimposing multiple signals.

[0086] Figure 3 A schematic diagram of the azimuth spectrum of dual-target broadband LFM signals processed by the present application and the prior art is shown.

[0087] Reference Figure 3 Compared with the broadband azimuth spectrum obtained by processing with the prior art, it can be seen that the broadband azimuth spectrum obtained by the present application has a narrower main lobe and lower side lobes, can achieve aperture expansion, and obtain higher spatial gain and higher azimuth resolution.

[0088] Reference Figure 2 and Figure 3 , compared with the narrowband azimuth spectrum obtained by processing in this application, it can be seen that the broadband azimuth spectrum obtained by processing in this application has more stable side lobes than the narrowband processing side lobes.

[0089] Furthermore, in one embodiment, the product of the length of the snapshot data and the total number of snapshots is smaller than the time correlation radius of the signal of the target frequency.

[0090] In this embodiment, the time correlation radius reflects the maximum time range in which the signal maintains significant correlation in the time dimension. The product of the length of the snapshot data and the total number of snapshots is the time span of snapshot data acquisition. When the time span of snapshot data acquisition is smaller than the time correlation radius, it can ensure that the collected signal has good correlation, which is beneficial to the synthetic aperture.

[0091] In a second aspect, an embodiment of the present application also provides a linear array passive synthetic aperture device.

[0092] Figure 4 A schematic diagram of the functional modules of a linear array passive synthetic aperture device in one embodiment of the present application is shown.

[0093] Reference Figure 4 In one embodiment, the linear array passive synthetic aperture device includes:

[0094] A beamforming module 10 is configured to divide the i-th snapshot data of the linear array into an upper half array and a lower half array, perform beamforming at a target azimuth and a target frequency, and obtain an initial result of the upper half array and an initial result of the lower half array of the i-th snapshot data, wherein the product of the length of the snapshot data and the total number of snapshots is less than the time correlation radius of the signal at the target frequency, i is any positive integer in the range [1, M], and M is the total number of snapshots;

[0095] a phase difference calculation module 20 for calculating the phase difference of the m+1th snapshot data based on the initial result of the first half of the m+1th snapshot data and the initial result of the second half of the mth snapshot data, where m is any positive integer in the range of [1, M-1];

[0096] A phase compensation module 30 is configured to accumulate and compensate the phase differences of the second to (m+1)th snapshot data to a target initial result of the (m+1)th snapshot data to obtain a compensated result for the (m+1)th snapshot data, where the target initial result is a lower-half initial result or a full-half initial result, and the full-half initial result is composed of the upper-half initial result and the lower-half initial result.

[0097] The coherent superposition module 40 is used to coherently superpose the target initial result of the first snapshot data and the compensation results of the second to M-th snapshot data to obtain a narrowband synthetic aperture azimuth spectrum of the target azimuth angle at the target frequency.

[0098] Furthermore, in one embodiment, the linear array passive synthetic aperture device further includes an incoherent superposition module, configured to:

[0099] The narrowband synthetic aperture azimuth spectra of the target azimuth at multiple target frequencies are incoherently superimposed to obtain the broadband synthetic aperture output azimuth spectrum of the target azimuth.

[0100] Furthermore, in one embodiment, the calculation formulas for the initial results of the first half of the i-th snapshot data and the initial results of the second half of the i-th snapshot data are:

[0101]

[0102] in, are the initial results of the upper and lower half arrays of the i-th snapshot data, f is the target frequency, θ is the target azimuth, are the upper half frequency domain signal and the lower half frequency domain signal of the i-th snapshot data at the target frequency, are the upper half array weighted vector and the lower half array weighted vector of the target azimuth and target frequency respectively. The upper half array weighted vector and the lower half array weighted vector differ by a phase offset, which can be expressed as:

[0103]

[0104] Among them, H represents the conjugate transpose, N is the number of array elements, is the phase difference between array elements corresponding to the target azimuth angle, d is the array element spacing, and c is the speed of sound.

[0105] Furthermore, in one embodiment, the calculation formula for the compensation result of the (m+1)th snapshot data is:

[0106]

[0107] in, is the compensation result of the m+1th snapshot data, B m+1 (θ,f) is the target initial result of the m+1th snapshot data, is the phase difference of the x+1th snapshot data.

[0108] Furthermore, in one embodiment, the product of the length of the snapshot data and the total number of snapshots is smaller than the time correlation radius of the signal of the target frequency.

[0109] Furthermore, in one embodiment, the weighting method used in beamforming is conventional beamforming weighting, Barnes-Noble Filter weighting, or adaptive weighting.

[0110] Furthermore, in one embodiment, the phase difference calculation method is a cross-correlation method, a multi-frequency point averaging method or a least squares method.

[0111] Among them, the functional implementation of each module in the above-mentioned linear array passive synthetic aperture device corresponds to the various steps in the above-mentioned linear array passive synthetic aperture method embodiment, and their functions and implementation processes will not be repeated here one by one.

[0112] In a third aspect, an embodiment of the present application provides a linear array passive synthetic aperture device, which may be a personal computer (PC), a laptop computer, a server, or other device with data processing capabilities.

[0113] Figure 5 A schematic diagram of the hardware structure of a linear array passive synthetic aperture device involved in an embodiment of the present application is shown.

[0114] Reference Figure 5 In an embodiment of the present application, a linear array passive synthetic aperture device may include a processor, a memory, a communication interface, and a communication bus.

[0115] The communication bus may be of any type and is used to interconnect the processor, memory, and communication interface.

[0116] Communication interfaces include input / output (I / O) interfaces, physical interfaces, and logical interfaces, used to interconnect components within the linear array passive synthetic aperture device (LAPSD), as well as interfaces used to interconnect the LAPSD with other devices (e.g., other computing devices or user equipment). Physical interfaces can include Ethernet, fiber, or ATM interfaces; user equipment can include displays, keyboards, and other devices.

[0117] The memory can be various types of storage media, such as random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), flash memory, optical storage, hard disk, programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), etc.

[0118] The processor may be a general-purpose processor that can call a linear array passive synthetic aperture program stored in a memory and execute the linear array passive synthetic aperture method provided in the embodiments of the present application. For example, the general-purpose processor may be a central processing unit (CPU). The method executed when the linear array passive synthetic aperture program is called can be referenced from the various embodiments of the linear array passive synthetic aperture method of the present application and will not be further described here.

[0119] Those skilled in the art will understand that Figure 5 The hardware structure shown in the figure does not constitute a limitation to the present application and may include more or fewer components than shown in the figure, or a combination of certain components, or a different arrangement of components.

[0120] In a fourth aspect, an embodiment of the present application also provides a readable storage medium.

[0121] The readable storage medium of the present application stores a linear array passive synthetic aperture program, wherein when the linear array passive synthetic aperture program is executed by a processor, the steps of the linear array passive synthetic aperture method as described above are implemented.

[0122] Among them, the method implemented when the linear array passive synthetic aperture program is executed can refer to the various embodiments of the linear array passive synthetic aperture method of the present application, and will not be repeated here.

[0123] It should be noted that the serial numbers of the above-mentioned embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0124] The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices. The terms "first", "second" and "third" are used to distinguish different objects, etc., and do not represent a sequence, nor do they limit the "first", "second" and "third" to different types.

[0125] In the description of the embodiments of this application, the words "exemplary," "for example," or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary," "for example," or "for example" in the embodiments of this application should not be construed as being preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary," "for example," or "for example" is intended to present the relevant concepts in a concrete manner.

[0126] In the description of the embodiments of the present application, unless otherwise specified, “ / ” means or, for example, A / B can mean A or B; “and / or” in the text is merely a description of the association relationship of associated objects, indicating that three relationships may exist, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present application, “multiple” refers to two or more than two.

[0127] In some processes described in the embodiments of the present application, multiple operations or steps are included that appear in a specific order. However, it should be understood that these operations or steps may not be performed in the order in which they appear in the embodiments of the present application or may be performed in parallel. The sequence numbers of the operations are only used to distinguish between different operations, and the sequence numbers themselves do not represent any order of execution. In addition, these processes may include more or fewer operations, and these operations or steps may be performed in sequence or in parallel, and these operations or steps may be combined.

[0128] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus the necessary general hardware platform, of course, it can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) as described above, and includes a number of instructions for enabling a terminal device to execute the methods described in each embodiment of the present application.

[0129] The above are only preferred embodiments of the present application and do not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A linear array passive synthetic aperture method, characterized in that: The linear array passive synthetic aperture method comprises: The i-th snapshot data of the linear array is divided into the upper half array and the lower half array, and beamforming is performed on the target azimuth and target frequency to obtain the initial results of the upper half array and the lower half array of the i-th snapshot data, where i is a positive integer in the range [1, M] and M is the total number of snapshots; The phase difference of the m+1th snapshot data is calculated based on the initial result of the upper half array of the m+1th snapshot data and the initial result of the lower half array of the mth snapshot data, where m is any positive integer in the range of [1, M-1]. Accumulate and compensate the phase differences of the 2nd to (m+1th) snapshot data to the target initial result of the (m+1th) snapshot data to obtain the compensation result of the (m+1th) snapshot data, where the target initial result is the lower half array initial result or the full array initial result, and the full array initial result is composed of the upper half array initial result and the lower half array initial result; The target initial result of the first snapshot data and the compensation results of the second to M-th snapshot data are coherently superimposed to obtain a narrowband synthetic aperture azimuth spectrum of the target azimuth angle at the target frequency.

2. The linear array passive synthetic aperture method according to claim 1, wherein: After the step of coherently superposing the target initial result of the first snapshot data and the compensation results of the second to M-th snapshot data to obtain a narrowband synthetic aperture azimuth spectrum of the target azimuth angle at the target frequency, the method further includes: The narrowband synthetic aperture azimuth spectra of the target azimuth at multiple target frequencies are incoherently superimposed to obtain the broadband synthetic aperture output azimuth spectrum of the target azimuth.

3. The linear array passive synthetic aperture method according to claim 1, wherein: The calculation formula for the initial results of the first half and the second half of the i-th snapshot data is: in, are the initial results of the upper and lower half arrays of the i-th snapshot data, f is the target frequency, θ is the target azimuth, are the upper half frequency domain signal and the lower half frequency domain signal of the i-th snapshot data at the target frequency, are the upper half array weighted vector and the lower half array weighted vector of the target azimuth and target frequency respectively. The upper half array weighted vector and the lower half array weighted vector differ by a phase offset, which can be expressed as: Among them, H represents the conjugate transpose, N is the number of array elements, is the phase difference between array elements corresponding to the target azimuth angle, d is the array element spacing, and c is the speed of sound.

4. The linear array passive synthetic aperture method according to claim 1, wherein: The calculation formula for the compensation result of the m+1th snapshot data is: in, is the compensation result of the m+1th snapshot data, B m+1 (θ,f) is the target initial result of the m+1th snapshot data, is the phase difference of the x+1th snapshot data.

5. The linear array passive synthetic aperture method according to any one of claims 1 to 4, characterized in that: The product of the length of the snapshot data and the total number of snapshots is smaller than the time correlation radius of the signal of the target frequency.

6. The linear array passive synthetic aperture method according to any one of claims 1 to 4, characterized in that: The weighting method used in beamforming is conventional beamforming weighting, c or adaptive weighting.

7. The linear array passive synthetic aperture method according to any one of claims 1 to 4, characterized in that: The phase difference is calculated by a cross-correlation method, a multi-frequency point averaging method or a least squares method.

8. A linear array passive synthetic aperture device, characterized in that: The linear array passive synthetic aperture device comprises: A beamforming module is configured to divide the i-th snapshot data of the linear array into an upper array and a lower array, and perform beamforming on the target azimuth and target frequency to obtain an initial result of the upper array and an initial result of the lower array for the i-th snapshot data. The product of the snapshot data length and the total number of snapshots is less than the time correlation radius of the signal at the target frequency, i is a positive integer in the range [1, M], and M is the total number of snapshots. a phase difference calculation module, configured to calculate a phase difference of the m+1th snapshot data based on an initial result of an upper half array of the m+1th snapshot data and an initial result of a lower half array of the mth snapshot data, where m is any positive integer in the range of [1, M-1]; a phase compensation module, configured to accumulate and compensate the phase differences of the second to m+1th snapshot data to a target initial result of the m+1th snapshot data to obtain a compensation result of the m+1th snapshot data, where the target initial result is a lower-half array initial result or a full-array initial result, and the full-array initial result is composed of an upper-half array initial result and a lower-half array initial result; The coherent superposition module is used to coherently superpose the target initial result of the first snapshot data and the compensation results of the second to M-th snapshot data to obtain a narrowband synthetic aperture azimuth spectrum of the target azimuth angle at the target frequency.

9. A linear array passive synthetic aperture device, characterized in that: The linear array passive synthetic aperture device includes a processor, a memory, and a linear array passive synthetic aperture program stored in the memory and executable by the processor, wherein when the linear array passive synthetic aperture program is executed by the processor, the steps of the linear array passive synthetic aperture method as described in any one of claims 1 to 7 are implemented.

10. A readable storage medium, characterized in that: The readable storage medium stores a linear array passive synthetic aperture program, wherein when the linear array passive synthetic aperture program is executed by a processor, the steps of the linear array passive synthetic aperture method according to any one of claims 1 to 7 are implemented.

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