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

Abstract

The invention provides a linear array passive synthetic aperture method, device and equipment and a readable storage medium, and the method comprises the steps: dividing the ith snapshot data of a linear array into an upper half array and a lower half array, and carrying out the beam forming 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 ith snapshot data; calculating the phase difference of the (m + 1)-th snapshot data according to the initial result of the upper half array of the (m + 1)-th snapshot data and the initial result of the lower half array of the (m + 1)-th snapshot data; accumulating and compensating 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 compensation result of the (m + 1) th snapshot data; and performing coherent superposition on the target initial result of the first snapshot data and the compensation results of the second snapshot data to the Mth snapshot data to obtain a narrowband synthetic aperture azimuth spectrum of the target azimuth angle on the target frequency. According to the invention, the synthetic aperture does not require array element overlapping, and can adapt to a multi-target scene.

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, device, equipment and readable storage medium. Background Art

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

[0003] At present, the passive synthetic aperture algorithm is limited to the method of spatial overlap of some array elements. The phase difference caused by relative motion is calculated by overlapping array elements, and then compensated to the non-overlapping array element signal, so as to finally achieve array expansion. For example, algorithms such as ETAM (Extended Towed Array Measurement) and FFTSA (Fast Fourier Transform Synthetic Aperture) have high requirements for the array posture and need to ensure the existence of overlapping array elements. Research on passive synthetic aperture technology focuses on improving the accuracy of phase difference estimation of overlapping array elements. Therefore, the performance of current passive synthetic aperture algorithms is seriously degraded when the overlapping of array elements is difficult to accurately control due to factors such as the inaccurately known motion speed and the uncertain array motion posture. Summary of the invention

[0004] The present application provides a linear array passive synthetic aperture method, device, equipment and readable storage medium, which can solve the technical problem in the prior art that the performance of the passive synthetic aperture algorithm is seriously degraded when the 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 array and the lower array to perform beamforming on the target azimuth and the target frequency, and the initial results of the upper array and the lower array of the i-th snapshot data are obtained, where i is a positive integer in the range of [1, M], and M is the total number of snapshots;

[0007] The phase difference of the m+1th snapshot data is calculated according to 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, wherein 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 Mth snapshot data are coherently superimposed to obtain a narrow-band synthetic aperture azimuth spectrum of the target azimuth angle at the target frequency.

[0010] Further, in one embodiment, after the step of coherently superposing the target initial result of the first snapshot data and the compensation results of the second to Mth 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 a wideband synthetic aperture output azimuth spectrum of the target azimuth.

[0012] Further, 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 as follows:

[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 array weighted vector and lower array weighted vector of the target azimuth and target frequency respectively. The upper array weighted vector and the lower array weighted vector differ by a phase offset, which can be expressed as:

[0016]

[0017] Where H represents the conjugate transpose, N is the number of array elements, is the phase difference between array elements corresponding to the target azimuth, 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 used to divide the i-th snapshot data of the linear array into an upper array and a lower array to perform beamforming at a target azimuth and a target frequency, and obtain an initial result of the upper array and an initial result of the lower 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 of the target frequency, i is each positive integer in the range of [1,M], and M is the total number of snapshots;

[0026] A phase difference calculation module, used for calculating the phase difference of the m+1th snapshot data according to 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, wherein m is any positive integer in the range of [1, M-1];

[0027] A phase compensation module is used to accumulate and compensate the phase differences of the second 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, wherein 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;

[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 narrow-band 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, comprising 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 the present application, the snapshot data of the linear array is first divided into the upper and lower arrays for beam forming, and then the phase difference caused by the relative motion of the target and the linear array is calculated with the help of the lower array beam domain output of the former and the upper array beam domain output of the latter in adjacent snapshot data. The beam domain output of each snapshot data after the first is compensated with the help of the phase difference, so as 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 the present 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-noise ratio, and give full play to the advantage of the spatial coherence radius of the low-frequency signal. The time gain can be converted 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of a process flow of a linear array passive synthetic aperture method in one embodiment of the present application;

[0033] Figure 2 A schematic diagram of the azimuth spectrum of the present application and the prior art for processing dual-target single-frequency signals;

[0034] Figure 3 A schematic diagram of the azimuth spectrum of dual-target broadband LFM signals processed by the present 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 solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, 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 the present application clearer, the implementation methods of the present 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, the linear array passive synthetic aperture method comprises the following steps:

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

[0043] Specifically, the linear array includes N array elements arranged in a linear manner, 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 lower 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 array weighted vector and lower array weighted vector of the target azimuth and target frequency respectively. The upper array weighted vector and the lower array weighted vector differ by a phase offset, which can be expressed as:

[0047]

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

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

[0050] CBF weighting is based on the phase compensation of the received signal of each array element in the array, so that the signals in the desired direction are superimposed in phase to achieve beam pointing. The CBF weighting algorithm is simple, easy to implement and understand, with small calculation amount and low hardware requirements. It is suitable for scenarios with high real-time requirements and relatively simple interference environment.

[0051] The principle of BNF weighting is to maximize the output power of the target azimuth and make the output of the interference azimuth 0. BNF weighting achieves interference suppression by constructing a weight vector orthogonal to the interference array pop vector.

[0052] Adaptive weighting adjusts the weighting coefficients in real time according to 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, the adaptive weighting algorithm automatically adjusts the weighting coefficients according to the direction and strength of the interference signal, so that the beam can suppress interference while maintaining the gain of 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 still maintain good performance in complex and changeable interference environments. It can automatically optimize the beam direction according to different signal environments to improve the detection and resolution capabilities of target signals.

[0053] S2. Calculate the phase difference of the m+1th snapshot data according to 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].

[0054] Specifically, the calculation formula for the phase difference of the m+1th 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+1th 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 the phase difference based on the correlation between signals. The calculation is relatively simple and has a certain ability to suppress noise. If the noise is random and uncorrelated with the signal, the effect of the noise will be averaged when calculating the cross-correlation. The cross-correlation method is suitable for scenarios where the signal frequency is relatively single and the signal-to-noise ratio is high.

[0059] The multi-frequency averaging method is applicable to the case 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 the phase difference based on the idea of ​​minimizing the error. It has high accuracy and can accurately estimate the phase difference by minimizing the error in the presence of noise and interference. The least squares method is applicable to various types of signals as long as a suitable signal model can be established. The least squares method can also handle complex situations where the signal amplitude and phase change at the same time.

[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, which can be realized with B m (θ, f) are in phase, and further coherent superposition of outputs in different snapshot beam domains 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 the compensation result of the m+1th snapshot data, wherein the target initial result is the lower-array initial result or the full-array initial result, and the full-array initial result is composed of the upper-array initial result and the lower-array initial result.

[0072] Specifically, the phase difference of the m+1th snapshot data represents the phase difference caused by the relative motion between the target and the linear array during the m+1th snapshot process. In order to align the beam domain output of the m+1th snapshot data to the initial reference point, that is, the position corresponding to the linear array during the 1st snapshot process, the phase difference of the 2nd to m+1th snapshot data needs to be accumulated as the compensation phase.

[0073] For example, the calculation formula for the compensation result of the m+1th 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 Mth snapshot data to obtain a narrow-band 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, where 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 beam forming, and then the phase difference caused by the relative motion of the target and the linear array is calculated with the help of the lower array beam domain output of the former and the upper array beam domain output of the latter in adjacent snapshot data. The beam domain output of each snapshot data after the first is compensated with the help of the phase difference, so as 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-noise ratio, and give full play to the advantage of the spatial coherence radius of the low-frequency signal. The time gain can be converted 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 the present application and the prior art processing of dual-target single-frequency signals is shown.

[0080] Reference Figure 2 Compared with the narrow-band azimuth spectrum obtained by processing in the prior art, the narrow-band azimuth spectrum obtained by the present application has a narrower main lobe and lower side lobes, and can achieve aperture expansion, 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. Among them, the towed linear array has formation distortion due to its special working mode, and it is difficult to achieve array element overlap. When using passive synthetic aperture algorithms such as ETAM and FFTSA that have high requirements for formation posture, the performance is seriously degraded. When using the algorithm of this application, the performance advantage is obvious.

[0082] Further, in one embodiment, after the step of coherently superposing the target initial result of the first snapshot data and the compensation results of the second to Mth 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 a wideband synthetic aperture output azimuth spectrum of the target azimuth.

[0084] Specifically, incoherent superposition refers to the operation of superimposing multiple signals without a fixed phase relationship or with a randomly changing phase relationship during signal processing. In incoherent superposition, due to the uncertainty of the phase relationship, the amplitude of the superimposed signal cannot be controlled by the 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 a narrowband. However, when applied to a wideband, a 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 the prior art, the broadband azimuth spectrum obtained by the present application has a narrower main lobe and lower side lobes, and can achieve aperture expansion, 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 the present application, it can also be seen that the broadband azimuth spectrum obtained by processing in the present 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 acquired 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 comprises:

[0094] The beamforming module 10 is used to divide the i-th snapshot data of the linear array into an upper array and a lower array to perform beamforming at a target azimuth and a target frequency, and obtain an initial result of the upper array and an initial result of the lower 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 of the target frequency, i is each positive integer in the range of [1, M], and M is the total number of snapshots;

[0095] A phase difference calculation module 20 is used to calculate the phase difference of the m+1th snapshot data according to 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];

[0096] The phase compensation module 30 is used to accumulate and compensate the phase differences of the second 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, wherein 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;

[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 narrow-band 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, which is used to:

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

[0100] Further, 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 as follows:

[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 array weighted vector and lower array weighted vector of the target azimuth and target frequency respectively. The upper array weighted vector and the lower array weighted vector differ by a phase offset, which can be expressed as:

[0103]

[0104] Where H represents the conjugate transpose, N is the number of array elements, is the phase difference between array elements corresponding to the target azimuth, 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 its 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, the memory, and the communication interface.

[0116] The communication interface includes input / output (I / O) interface, physical interface and logical interface, etc., which are used to realize the interconnection of devices inside the linear array passive synthetic aperture device, and the interface used to realize the interconnection between the linear array passive synthetic aperture device and other devices (such as other computing devices or user devices). The physical interface can be an Ethernet interface, a fiber optic interface, an ATM interface, etc.; the user device can be a display, a keyboard, etc.

[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, and the general-purpose processor may call the linear array passive synthetic aperture program stored in the memory and execute the linear array passive synthetic aperture method provided in the embodiment 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 may refer to the various embodiments of the linear array passive synthetic aperture method of the present application, and will not be repeated here.

[0119] Those skilled in the art will understand that Figure 5 The hardware structure shown in the figure does not constitute a limitation on the present application, and may include more or less components than shown in the figure, or combine certain components, or arrange the components differently.

[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 only for description 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 "first", "second" and "third" to different types.

[0125] In the description of the embodiments of the present application, "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 the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary", "for example" or "for example" is intended to present related concepts in a specific way.

[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; the “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 that appear in a specific order are included, but it should be understood that these operations or steps may not be executed in the order in which they appear in the embodiments of the present application or in parallel, and the sequence number of the operation is only used to distinguish the different operations, and the sequence number itself does not represent any execution order. In addition, these processes may include more or fewer operations, and these operations or steps may be executed 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 a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application is essentially 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, disk, CD) as described above, and includes a number of instructions for 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 are not intended to 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 array and the lower array to perform beamforming on the target azimuth and the target frequency, and the initial results of the upper array and the lower array of the i-th snapshot data are obtained, where i is a positive integer in the range of [1, M], and M is the total number of snapshots; The phase difference of the m+1th snapshot data is calculated according to 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, wherein 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 Mth snapshot data are coherently superimposed to obtain a narrow-band 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, characterized in that: After the step of coherently superposing the target initial result of the first snapshot data and the compensation results of the second to Mth 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 a wideband synthetic aperture output azimuth spectrum of the target azimuth.

3. The linear array passive synthetic aperture method according to claim 1, characterized in that: 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 array weighted vector and lower array weighted vector of the target azimuth and target frequency respectively. The upper array weighted vector and the lower array weighted vector differ by a phase offset, which can be expressed as: Where H represents the conjugate transpose, N is the number of array elements, is the phase difference between array elements corresponding to the target azimuth, 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, characterized in that: 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 calculation method is the cross-correlation method, the multi-frequency point average method or the 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 used to divide the i-th snapshot data of the linear array into an upper array and a lower array to perform beamforming at a target azimuth and a target frequency, and obtain an initial result of the upper array and an initial result of the lower 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 of the target frequency, i is each positive integer in the range of [1,M], and M is the total number of snapshots; A phase difference calculation module, used for calculating the phase difference of the m+1th snapshot data according to 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, wherein m is any positive integer in the range of [1, M-1]; A phase compensation module is used to accumulate and compensate the phase differences of the second 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, wherein 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 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 narrow-band 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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