Multi-receiving-array synthetic aperture sonar imaging method and device considering intra-pulse motion

Abstract

The invention discloses a multi-receiving-array synthetic aperture sonar imaging method and device considering intra-pulse motion, and the method comprises the steps: building an echo baseband signal model in a two-dimensional plane under the condition that the relative motion speed of a platform in a signal transmitting and receiving pulse width is not changed in a pulse repetition period; performing error analysis on envelope time delay and phase of an echo baseband signal in the echo baseband signal model based on the waveform scaling factor, and determining an approximate signal model of the echo baseband signal model; solving a two-dimensional frequency spectrum of an approximate echo baseband signal in the approximate signal model; based on the two-dimensional frequency spectrum, focusing is completed by using a single-station imaging algorithm to obtain a multi-receiving-array synthetic aperture sonar imaging result, multi-receiving-array synthetic aperture sonar imaging under the condition of considering intra-pulse motion is realized, and the resolution of underwater imaging is improved.

Description

Technical Field

[0001] The present application relates to the field of underwater surveying and mapping, and more specifically, to a multi-receiving array synthetic aperture sonar imaging method and device taking intra-pulse motion into consideration. Background Art

[0002] Multi-subarray synthetic aperture sonar is widely used in seabed topography mapping because its azimuth resolution is higher than that of side-scan sonar. The movement of the platform (i.e., sonar platform) between the transmitted pulse and the received pulse is called inter-pulse motion. Here, unlike the stop-and-go model in synthetic aperture radar, the inter-pulse motion in synthetic aperture sonar cannot be ignored, so a non-stop-and-go model is generally used in synthetic aperture sonar. The movement within the width of the transmitted pulse and the received pulse is called intra-pulse motion. When the platform moves at high speed or the pulse time is long, the intra-pulse motion cannot be ignored, and it is manifested as the expansion and contraction of the waveform in the time domain.

[0003] At present, in frequency modulated continuous wave synthetic aperture radar or high altitude high speed motion synthetic aperture radar imaging, due to the long pulse time and fast platform speed, the intra-pulse motion is generally approximated as Doppler frequency shift, and all of them are improvements based on the stop-and-go model, which is not applicable in sonar. The research on the Doppler effect in related multi-receiver array synthetic aperture sonar is also based on the stop-and-go assumption and the back propagation algorithm. It is not combined with the frequency domain line-by-line algorithm and requires a lot of computing resources. It is impossible to achieve real-time, high-resolution imaging while considering the intra-pulse motion.

[0004] Therefore, it becomes an urgent problem to provide a method for realizing real-time, high-resolution multi-receiving array synthetic aperture sonar imaging while taking into account the intrapulse motion. Summary of the invention

[0005] In response to at least one defect or improvement need in the prior art, the present invention provides a multi-receiving array synthetic aperture sonar imaging method and device that takes intra-pulse motion into consideration, so that the imaging method can be applied to high-speed and large pulse width situations while taking intra-pulse motion into consideration, and can ensure high imaging resolution.

[0006] To achieve the above-mentioned purpose, according to the first aspect of the present invention, a multi-receiving array synthetic aperture sonar imaging method considering intra-pulse motion is provided, the method comprising: establishing an echo baseband signal model in a two-dimensional plane under the condition that the relative motion speed of the platform within the width of the signal transmission and reception pulses remains unchanged within a pulse repetition period; performing error analysis on the envelope delay and phase of the echo baseband signal in the echo baseband signal model based on a waveform stretching factor to determine an approximate signal model of the echo baseband signal model; solving the two-dimensional spectrum of the approximate echo baseband signal in the approximate signal model; and completing focusing based on the two-dimensional spectrum using a single-station imaging algorithm to obtain a multi-receiving array synthetic aperture sonar imaging result.

[0007] In an exemplary embodiment, the establishment of an echo baseband signal model in a two-dimensional plane under the condition that the relative movement speed of the platform within the signal transmission and reception pulse width remains unchanged within a pulse repetition period includes: determining the relative speed of the transmitting array in a multi-receiving array synthetic aperture sonar with respect to the target as the relative movement speed of the platform within the signal transmission and reception pulse width; determining the echo signal of each receiving array in the multi-receiving array synthetic aperture sonar based on the relative speed; and demodulating the echo signal to remove the carrier frequency to obtain the echo baseband signal.

[0008] In an exemplary embodiment, determining the approximate signal model of the echo baseband signal model includes: obtaining a first analysis result by performing an approximate error analysis on a first error factor, wherein the first error factor affects the envelope delay and phase of the echo signal; obtaining a second analysis result by performing an approximate error analysis on a second error factor, wherein the second error factor affects the envelope delay of the echo signal; obtaining a third analysis result by performing an approximate error analysis on a third error factor, wherein the third error factor affects the phase of the echo signal; and obtaining the approximate echo baseband signal based on the first analysis result, the second analysis result and the third analysis result.

[0009] In an exemplary embodiment, solving the two-dimensional spectrum of the approximate echo baseband signal in the approximate signal model includes: acquiring the range frequency domain signal of the approximate echo baseband signal; and determining the range phase dwell time of the range frequency domain signal according to the phase dwell principle.

[0010] In an exemplary embodiment, after determining the range-direction phase dwell time of the range-frequency domain signal, the method further includes: determining the propagation time at the equivalent phase center as the signal propagation time of the approximate echo signal, determining the distance history of the approximate echo baseband signal; and solving the two-dimensional spectrum of the approximate echo baseband signal in the approximate signal model based on the distance history.

[0011] In an exemplary embodiment, focusing is completed based on the two-dimensional spectrum using a single-station imaging algorithm to obtain a focusing result of a multi-receiving array synthetic aperture sonar imaging, including: compensating a fixed phase term in the two-dimensional time domain in the two-dimensional spectrum, wherein the fixed phase term is a corresponding first phase multiplication factor; performing range compression after Fourier transform in the range-frequency domain using a second phase multiplication factor; and performing envelope delay compensation in the range-frequency domain using a third phase multiplication factor.

[0012] In an exemplary embodiment, the method further includes: obtaining an azimuth time domain reconstruction result of the two-dimensional spectrum by inverse Fourier transform in the range frequency domain; and combining the azimuth time domain reconstruction result with a single-station imaging algorithm to obtain the focusing result of the multi-receiving array synthetic aperture sonar imaging.

[0013] According to the second aspect of the present invention, there is also provided a multi-receiving array synthetic aperture sonar imaging device taking into account intra-pulse motion, which comprises: an establishing unit for establishing an echo baseband signal model in a two-dimensional plane under the condition that the relative motion speed of the platform within the signal transmission and reception pulse width remains unchanged within a pulse repetition period; a first determining unit for performing error analysis on the envelope delay and phase of the echo baseband signal in the echo baseband signal model based on a waveform stretching factor, and determining an approximate signal model of the echo baseband signal model; a first solving unit for solving the two-dimensional spectrum of the approximate echo baseband signal in the approximate signal model; and an imaging unit for completing focusing based on the two-dimensional spectrum using a single-station imaging algorithm to obtain a multi-receiving array synthetic aperture sonar imaging result.

[0014] According to a third aspect of the present invention, there is also provided a computer-readable storage medium, in which a computer program is stored, wherein the computer program is configured to execute the above-mentioned multi-receiving array synthetic aperture sonar imaging method considering intra-pulse motion when running.

[0015] According to a fourth aspect of the present invention, there is also provided an electronic device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor executes the multi-receiving array synthetic aperture sonar imaging method taking into account intrapulse motion through the computer program.

[0016] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0017] (1) The present invention provides a multi-receiving array synthetic aperture sonar imaging method that takes intra-pulse motion into consideration. First, the relative motion speed of the platform within the width of the signal transmission and reception pulses is considered, and it is assumed that the relative motion speed is constant within a pulse repetition period, and an echo baseband signal model that takes intra-pulse motion into consideration is established in a two-dimensional plane. On this basis, the influence of the relative motion speed (waveform stretching factor) on the time delay and phase of the signal model is analyzed, and through error analysis, a certain approximation is made to the model to facilitate subsequent processing. The resident phase principle is utilized, and the distance history under the phase center approximation is adopted to solve the two-dimensional spectrum of the approximated echo baseband signal. The envelope offset and phase error caused by the micro-distance migration caused by the phase center approximation distance history are corrected, and focusing can be completed in combination with the single-station imaging algorithm.

[0018] (2) The multi-receiving array synthetic aperture sonar imaging method considering the intra-pulse motion provided by the present invention is adopted. The echo baseband signal model considering the intra-pulse motion is more accurate than the current non-stop-and-go model, and can be applied to high-speed, large pulse width and other situations. Within the allowable error range, the influence of the intra-pulse motion on the signal envelope and phase is analyzed, rather than simply approximating the intra-pulse motion as a frequency shift, so it is more accurate; the distance history based on the phase center approximation is adopted, and the phase dwell principle is used to obtain a two-dimensional spectrum that is completely analytical; any frequency domain line-by-line imaging algorithm can be combined with the obtained two-dimensional spectrum, which has universal applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 A schematic flow chart of an optional multi-receiving array synthetic aperture sonar imaging method considering intra-pulse motion provided in an embodiment of the present application;

[0021] Figure 2 A schematic diagram of the positional relationship between an optional synthetic aperture sonar transmitting array and a receiving array provided in an embodiment of the present application;

[0022] FIG3( a) is a schematic diagram of an optional first error factor provided in an embodiment of the present application;

[0023] FIG3( b ) is a schematic diagram of another optional first error factor provided in an embodiment of the present application;

[0024] Figure 4 A schematic diagram of an optional second error factor provided in an embodiment of the present application;

[0025] Figure 5 A schematic diagram of an optional third error factor provided in an embodiment of the present application;

[0026] Figure 6 A schematic flow chart of an optional multi-receiving array synthetic aperture sonar imaging method considering intra-pulse motion provided in an embodiment of the present application;

[0027] Figure 7 A schematic diagram of a point target focusing result of a multi-receiving array synthetic aperture sonar imaging taking into account intra-pulse motion provided in an optional embodiment of the present application;

[0028] Figure 8 A schematic diagram of the structure of an optional multi-receiving array synthetic aperture sonar imaging device considering intra-pulse motion provided in an embodiment of the present application;

[0029] Fig. 9 A schematic diagram of the structure of an optional electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] The terms "first", "second", "third", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof 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.

[0032] According to one aspect of the embodiments of the present application, a multi-receiving array synthetic aperture sonar imaging method considering intra-pulse motion is provided. Figure 1 The multi-receiving array synthetic aperture sonar imaging method considering intra-pulse motion provided by an embodiment of the present application is described.

[0033] Figure 1 FIG. 1 is a flow chart of an optional multi-receiving array synthetic aperture sonar imaging method considering intra-pulse motion provided by an embodiment of the present application, such as Figure 1 As shown, the process includes the following steps:

[0034] S102, establishing an echo baseband signal model in a two-dimensional plane under the condition that the relative movement speed of the platform within the width of the signal transmission and reception pulses remains unchanged within a pulse repetition period;

[0035] S104, performing error analysis on the envelope delay and phase of the echo baseband signal in the echo baseband signal model based on the waveform stretching factor, and determining an approximate signal model of the echo baseband signal model;

[0036] S106, solving the two-dimensional spectrum of the approximate echo baseband signal in the approximate signal model;

[0037] S108, based on the two-dimensional spectrum, a single-station imaging algorithm is used to complete focusing, and a multi-receiving array synthetic aperture sonar imaging result is obtained.

[0038] The position change of the platform within the time width of a single pulse transmission and reception is usually called intra-pulse motion. This motion has a significant impact on imaging quality because it causes envelope delay and phase changes of the echo signal, thereby affecting imaging resolution.

[0039] The multi-receiving array synthetic aperture sonar imaging algorithm provided in this application can be applied to scenarios where the pulse width is large and the platform speed is fast while taking into account the intra-pulse motion. This method can achieve more accurate imaging of underwater terrain or targets.

[0040] In this embodiment, the relative movement speed of the platform within the width of the signal transmission and reception pulse is considered, and it is assumed that the relative movement speed is constant within a pulse repetition period, and an echo baseband signal model considering the intra-pulse movement is established in a two-dimensional plane; on the basis of this model, the influence of the relative movement speed (waveform expansion factor) on the envelope delay and phase of the signal model is analyzed, and through error analysis, a certain approximation is made to the model to facilitate subsequent processing. Using the resident phase principle and the distance history under the phase center approximation, the two-dimensional spectrum of the approximated echo baseband signal is solved, and the envelope offset and phase error caused by the micro-distance migration brought by the phase center approximation distance history are corrected. Finally, focusing can be completed by combining the single-station imaging algorithm.

[0041] When establishing a simulation model, simulation can be performed according to the parameters recorded in Table 1, which is a simulation system parameter table.

[0042] Table 1

[0043]

[0044]

[0045] For example, Figure 2A schematic diagram of the positional relationship between an optional synthetic aperture sonar transmitting array and a receiving array provided in an embodiment of the present application is shown in FIG. Figure 2 As shown in Figure 1, multi-receiver array synthetic aperture sonar (SAS) is an advanced high-resolution underwater imaging technology that uses multiple receiving arrays to increase the mapping rate. The SAS transmission signal is a linear frequency modulation signal, and the radial velocity between the SAS and the target P (underwater mapping target) is v r (t; r), the scattering intensity of the target is A 0 ; Let f c is the center frequency of the transmitted pulse signal; K r is the frequency modulation slope of the transmitted pulse signal; w r (·) is the envelope of the transmitted pulse signal; w a (·) is the antenna pattern weight; A 0 is the amplitude. Unless otherwise specified, the amplitude terms irrelevant to the imaging quality are ignored in the formula derivation in this application.

[0046] Optionally, assuming that the relative speed of the platform and the target remains unchanged within a pulse repetition period, for the convenience of processing, the relative speed of the transmitting array relative to the target is generally taken, and an echo baseband signal model in a two-dimensional plane can be established. After determining the echo baseband signal model, the waveform expansion factor can be determined based on the relative speed, and the envelope delay and phase of the echo baseband signal in the echo baseband signal model can be analyzed for errors. On the basis of the precise signal model, the approximate signal model is obtained by simplifying within the error allowable range. Then, the two-dimensional spectrum of the approximate echo baseband signal in the approximate signal model is solved, and focusing is completed by combining the two-dimensional spectrum with the single-station imaging algorithm to obtain the focusing result of multi-receiving array synthetic aperture sonar imaging, thereby realizing multi-receiving array synthetic aperture sonar imaging.

[0047] Through the above steps S102 to S108, an echo baseband signal model in a two-dimensional plane is established under the condition that the relative movement speed of the platform within the width of the signal transmission and reception pulses remains unchanged within a pulse repetition period; error analysis is performed on the envelope delay and phase of the echo baseband signal in the echo baseband signal model based on the waveform stretching factor to determine the approximate signal model of the echo baseband signal model; the two-dimensional spectrum of the approximate echo baseband signal in the approximate signal model is solved; based on the two-dimensional spectrum, focusing is completed using a single-station imaging algorithm to obtain a multi-receiving array synthetic aperture sonar imaging result, and the echo baseband signal model considering the intra-pulse motion is more accurate than the current non-stop-and-go model, and can be applied to situations such as high speed and large pulse width. Within the allowable error range, the influence of the intra-pulse motion on the signal envelope and phase is analyzed, rather than simply approximating the intra-pulse motion as a frequency shift, so it is more accurate; a distance history based on the phase center approximation is adopted, and the phase dwell principle is used to obtain a completely analytical two-dimensional spectrum; any frequency domain line-by-line imaging algorithm can be combined with the obtained two-dimensional spectrum, which has universal applicability.

[0048] In an exemplary embodiment, when the relative movement speed of the platform within the width of the signal transmission and reception pulses remains unchanged within a pulse repetition period, establishing the echo baseband signal model in a two-dimensional plane includes:

[0049] S11, determining the relative speed of the transmitting array relative to the target in the multi-receiving array synthetic aperture sonar as the relative movement speed of the platform within the width of the signal transmitting and receiving pulses;

[0050] S12, determining an echo signal of each receiving array in a multi-receiving array synthetic aperture sonar based on the relative velocity;

[0051] S13, demodulate the echo signal to remove the carrier frequency, and obtain an echo baseband signal.

[0052] In this embodiment, assuming that the time delay difference between signals received at different positions in a single hydrophone array is negligible, the relative speed of the transmitting array in the multi-receiving array synthetic aperture sonar relative to the target can be determined as the relative movement speed of the platform within the signal transmission and reception pulse width, and the echo signal of each receiving array in the multi-receiving array synthetic aperture sonar is determined based on the relative speed. Exemplarily, in the continuous motion state, the echo signal of the mth receiving array can be expressed as:

[0053]

[0054] In the formula, represents the waveform expansion factor (relative motion speed), represents the signal propagation time; c represents the underwater sound speed; v r (t) represents the radial velocity during the pulse transmission and reception, f cK is the carrier frequency of the transmitted pulse signal; r is the frequency modulation slope of the transmitted Chirp signal; τ and t represent the slow time and fast time respectively; A 0 is the amplitude. Unless otherwise specified, the amplitude terms that are irrelevant to the imaging quality are ignored in the following formula derivation.

[0055] w r (·) is the envelope of the transmitted pulse signal which is approximately rectangular and can be expressed as: r (τ) = rect(τ / T p ).

[0056] w a (·) is the two-way pattern weighting function of the transceiver array, and its expression can be:

[0057]

[0058] The original echo signal is demodulated to remove the carrier frequency. The expression of the demodulated echo baseband signal can be:

[0059]

[0060] In addition to affecting the envelope delay and phase of the signal, the stretch factor s will also cause changes in the frequency modulation slope and pulse width of the echo signal, which is reflected as the stretching or compression of the waveform in the time domain. The imaging process is actually the matched filtering of the demodulated echo signal. The demodulated echo baseband signal can be analyzed. The change in the frequency modulation slope will cause the filter to mismatch, widen the main lobe width (Impulse Response Width, IRW) and raise the side lobes.

[0061] Optionally, for pulse signals, the 4dB beam width can be used to determine the IRW size, and the quadratic phase error (QPE) can be used to quantitatively analyze the IRW widening degree. When the frequency modulation slope offset is ΔK and the pulse width is T p When the pulse center is defined as the reference origin, the QPE mismatch is the largest at both ends of the pulse width, and QPE can be expressed as:

[0062]

[0063] In general, when the IRW is widened by 2%, 5% and 10%, the corresponding QPE is 0.27π, 0.41π and 0.55π respectively. Because when the QPE is near 0.28π, the widening of the main lobe may cause the nearest side lobe to merge into the main lobe, whether the QPE exceeds 0.27π can be used to determine whether to consider the influence of the telescopic factor on the frequency modulation slope. At this time, the corresponding IRW widening is 2%. Using the parameters in Table 1 for simulation, the QPE can be obtained to be 0.018π, which is much smaller than 0.27π. Therefore, the influence of the telescopic factor s on the frequency modulation slope can be ignored, but the influence on the phase and delay cannot be ignored. Further, the phase in the echo baseband signal expression can be:

[0064]

[0065] Where:

[0066] τ 1,m (t; r) takes into account the influence of radial velocity on the basis of the traditional non-stop-go time, which will change the delay and phase of the signal, τ 2,m (t; r) only affects the delay, τ 3,m (t; r) will change the signal phase. In order to facilitate the subsequent azimuth Fourier transform, τ 1,m (t; r), τ 2,m (t; r) and τ 3,m (t; r) is simplified.

[0067] In an exemplary embodiment, determining an approximate signal model of the echo baseband signal model includes:

[0068] S21, obtaining a first analysis result by performing an approximate error analysis on a first error factor, wherein the first error factor affects an envelope delay and a phase of an echo signal;

[0069] S22, obtaining a second analysis result by performing an approximate error analysis on the second error factor, wherein the second error factor affects the envelope delay of the echo signal;

[0070] S23, obtaining a third analysis result by performing an approximate error analysis on the third error factor, wherein the third error factor affects the phase of the echo signal;

[0071] S24, obtaining an approximate echo baseband signal based on the first analysis result, the second analysis result and the third analysis result.

[0072] In the embodiment of the present application, since the obtained echo baseband signal expression is complex and not conducive to subsequent processing, it can be approximated within the error allowable range, and the signal receiving and transmitting time expression after considering the influence of the radial velocity of the pulse motion can be expressed. In an optional example, by adjusting the first error factor (such as τ 1,m (t; r)) to perform approximate error analysis to obtain a first analysis result, where the first error factor affects the envelope delay and phase of the echo signal; by adjusting the second error factor (e.g., τ 2,m (t; r)) to perform approximate error analysis to obtain a second analysis result, where the second error factor affects the envelope delay of the echo signal; by adjusting the third error factor (e.g., τ 3,m (t; r)) performs approximate error analysis to obtain a third analysis result. Here, the third error factor affects the phase of the echo signal. The following specifically performs approximate error analysis on the three error factors.

[0073] 1) τ 1,m (t; r) approximation error analysis

[0074]

[0075] If the radial velocity of the transmitting array is used, and it is assumed that the pulse transmission and reception period v r (t) = v·sinθ T unchanged, according to Figure 2 have The analytical expression of vr(t) can be obtained as:

[0076]

[0077] Will Expanding it into a first-order term of t, we can get τ 1,m The approximate expression of (t; r) is

[0078]

[0079] Among them, α 1 =v 2 / c 2 , the above approximation gives τ 1,m (t; r) brings an error, the dimension of which is time. The time error can be expressed as:

[0080]

[0081] Δτ can be adjusted according to the parameters shown in Table 1. 1,m (t; r) for simulation, Δτ 1,m (t; r) takes the maximum value Δτ at the edge of the beam 1,max,m (r), so we can get Δτ of different sub-matrices1,max,m (r) changes in the entire surveying band, as shown in Figure 3(a) and Figure 3(b). It can be seen that c·Δτ exists in the entire surveying band. 1，max，m (r)<<λ / 8 and c·Δτ 1，max，m (r)<<ρ r , so τ 1,m (t; r) is expressed as The error caused is negligible.

[0082] 2) τ 2,m (t; r) approximation error analysis

[0083] τ 2,m The expression of (t; r) is relatively complicated. 2,m (t; r) is expanded into a first-order term of t, then τ 2,m (t; r) can be approximately expressed as:

[0084] in, The total error caused by the above approximation is:

[0085]

[0086] Δτ can be adjusted according to the parameters shown in Table 1. 2,m (t; r) to simulate and obtain the edge sub-array The changing pattern in the whole surveying belt, such as Figure 4 As shown. Figure 4 It can be seen that there are Therefore, τ 2,m (t; r) is expressed as The error caused is negligible.

[0087] 3) τ 3,m (t; r) approximation error analysis

[0088] τ 3,m The expression of (t; r) is relatively complicated. If it is ignored directly, the error caused is:

[0089] Δτ 3,m (t; r) = τ 3,m (t; r)

[0090] According to the parameters shown in Table 1, Δτ 3,m (t; r) to simulate and obtain the edge sub-array The changing pattern in the whole surveying belt, such as Figure 5 As shown. Figure 5 It can be seen that there are Ignore τ 3,mThe phase error caused by (t; r) can be ignored.

[0091] After obtaining the above error analysis results, the approximate form of the echo baseband signal can be established. After the above three approximations, the baseband form of the echo signal at the target P(r,0) received by the mth receiving array can be expressed as:

[0092]

[0093] Let f c is the center frequency of the transmitted pulse signal; K r is the frequency modulation slope of the transmitted pulse signal; w r (·) is the envelope of the transmitted pulse signal; w a (·) is the antenna pattern weight; A 0 is the amplitude. Unless otherwise specified, the amplitude terms irrelevant to the imaging quality are ignored in the formula derivation below. Then the baseband form of the echo signal of the target P located at (r, 0) received by the mth receiving array can be expressed as:

[0094]

[0095] In an exemplary embodiment, solving the two-dimensional spectrum of the approximate echo baseband signal in the approximate signal model includes:

[0096] S31, obtaining a range frequency domain signal approximating an echo baseband signal;

[0097] S32, determining the range phase dwell time of the range frequency domain signal according to the phase dwell principle.

[0098] In the embodiment of the present application, the expression of the distance frequency domain signal is obtained as follows:

[0099]

[0100] The phase in the range frequency domain signal expression is:

[0101]

[0102] According to the phase dwell principle, The range phase dwell time can be obtained as:

[0103]

[0104] Furthermore, we can PSP,m (f r ,t;r) into In the result:

[0105]

[0106] In an exemplary embodiment, after determining the range phase dwell time of the range frequency domain signal, the method further includes:

[0107] S41, determining the propagation time at the equivalent phase center as the signal propagation time of the approximate echo signal, and determining the distance history of the approximate echo baseband signal;

[0108] S42, solving the two-dimensional spectrum of the approximate echo baseband signal in the approximate signal model based on the distance history.

[0109] In the present application example, Figure 2 The propagation time corresponding to the effective phase center (EPC) in Then the distance history can be expressed as:

[0110]

[0111] Where ΔR m (r) represents micro-distance migration, and the expression can be:

[0112] ΔR m (r) = (2vr / c + d m ) 2 / (4r)

[0113] Further, the azimuth Fourier transform is performed to obtain

[0114]

[0115] According to the phase dwell principle, The range phase dwell time can be obtained as:

[0116]

[0117] Where:

[0118] t PSP,m (f r ,f a ; r) bring in Then D 2df Expand to f r The quadratic term of It can be expressed as:

[0119]

[0120] Among them, the following conditions are met:

[0121]

[0122] The first term in the expression is the azimuth modulation term; the second term is the impact caused by non-stop-and-go operation; the first two terms can be unified in the range Doppler to compensate through azimuth compression. The third term is the transmission signal modulation term, which is the source of range pulse compression; the fourth term is the Doppler frequency linear phase term caused by the separation of transmission and reception, which can be compensated by azimuth frequency domain reconstruction or time domain reconstruction; the fifth term is the second-order coupling term of range and azimuth, which needs to be compensated by secondary range compression; the sixth term is the linear phase term of range frequency, which corresponds to the range migration (Range Cell Migration, RCM), which will cause envelope offset and needs to be compensated by delay correction; the seventh term is the linear phase of the carrier, which will change the phase of the signal and needs to be compensated by phase correction before azimuth reconstruction. If α is set 1 =0, α 2 =0, then It will degenerate into the traditional two-dimensional spectrum, which also explains that under high speed conditions, it will cause α 1 and α 2 Determines additional envelope offset and phase change.

[0123] In an exemplary embodiment, focusing is performed by combining a two-dimensional spectrum with a single-station imaging algorithm to obtain a multi-receiver array synthetic aperture sonar imaging result, including:

[0124] S51, compensating a fixed phase term in a two-dimensional time domain in a two-dimensional spectrum, wherein the fixed phase term is a corresponding first phase multiplication factor;

[0125] S52, performing range compression after Fourier transform in the range frequency domain by using a second phase multiplication factor;

[0126] S53, performing envelope delay compensation in the distance frequency domain by using a third phase multiplication factor.

[0127] In the embodiments of the present application, Figure 6 As shown, FFT is fast Fourier transform; IFFT is fast inverse Fourier transform. The present invention is further described below in conjunction with the accompanying drawings and embodiments. According to the aforementioned two-dimensional spectrum, each subarray is micro-migrated to eliminate ΔR m The envelope offset and phase error caused by (r) are first compensated in the two-dimensional time domain for the fixed phase term, and the corresponding phase multiplication factor (first phase multiplication factor) is:

[0128]

[0129] Then, after Fourier transform in the distance frequency domain, distance compression is performed, and the phase multiplication factor (second phase multiplication factor) is:

[0130]

[0131] In the distance frequency domain, envelope delay compensation is performed, and the corresponding phase multiplication factor (the third phase multiplication factor) is:

[0132]

[0133] In the above formula: r c is the distance between the centers of the surveying bands, α 2,ref For c The value of .

[0134] In an exemplary embodiment, the method further comprises:

[0135] S61, obtaining the azimuth time domain reconstruction result of the two-dimensional spectrum through inverse Fourier transform in the range frequency domain;

[0136] S62, combining the azimuth time domain reconstruction result with the single-station imaging algorithm to obtain the multi-receiver array synthetic aperture sonar imaging result.

[0137] In the embodiment of the present application, the item related to the array element number in the signal has been eliminated, that is, after the conversion of the multi-subarray signal to the single array signal is completed, focusing can be completed by the traditional single-station imaging algorithm. Taking the range Doppler algorithm as an example, the focusing result obtained is as follows: Figure 6 As shown. Through the inverse Fourier transform of the range frequency domain, the azimuth time domain reconstruction result of the two-dimensional spectrum is obtained, and the azimuth time domain reconstruction result is combined with the single-station imaging algorithm to obtain the multi-receiver array synthetic aperture sonar focusing result (ie, imaging result).

[0138] According to another aspect of an embodiment of the present application, an imaging device for implementing the above-mentioned multi-receiving array synthetic aperture sonar imaging method considering intra-pulse motion is also provided. Figure 8 is a schematic structural diagram of an optional multi-receiving array synthetic aperture sonar imaging device considering intra-pulse motion according to an embodiment of the present application, such as Figure 8 As shown, the device may include:

[0139] The establishing unit 802 is used to establish the echo baseband signal model in the two-dimensional plane under the condition that the relative movement speed of the platform within the width of the signal transmission and reception pulses remains unchanged within a pulse repetition period;

[0140] A first determining unit 804 is configured to perform error analysis on an envelope delay and a phase of an echo baseband signal in the echo baseband signal model based on a waveform stretching factor, and determine an approximate signal model of the echo baseband signal model;

[0141] A first solving unit 806 is used to solve the two-dimensional spectrum of the approximate echo baseband signal in the approximate signal model;

[0142] The imaging unit 808 is used to complete focusing based on the two-dimensional spectrum using a single-station imaging algorithm to obtain a multi-receiving array synthetic aperture sonar imaging result.

[0143] It should be noted that the establishing unit 802 in this embodiment can be used to execute the above step S102, the first determining unit 804 in this embodiment can be used to execute the above step S104, the first solving unit 806 in this embodiment can be used to execute the above step S106, and the imaging unit 808 in this embodiment can be used to execute the above step S108.

[0144] Through the above modules, under the condition that the relative movement speed of the platform within the width of the signal transmission and reception pulses remains unchanged within a pulse repetition period, an echo baseband signal model in a two-dimensional plane is established; based on the waveform stretching factor, the envelope delay and phase of the echo baseband signal in the echo baseband signal model are analyzed for errors, and the approximate signal model of the echo baseband signal model is determined; the two-dimensional spectrum of the approximate echo baseband signal in the approximate signal model is solved; based on the two-dimensional spectrum, the single-station imaging algorithm is used to complete the focusing, and the multi-receiving array synthetic aperture sonar imaging result is obtained. The echo baseband signal model considering the intra-pulse motion is more accurate than the current non-stop-and-go model, and can be applied to situations such as high speed and large pulse width. Within the allowable error range, the influence of the intra-pulse motion on the signal envelope and phase is analyzed, rather than simply approximating the intra-pulse motion as a frequency shift, so it is more accurate; the distance history based on the phase center approximation is adopted, and the phase dwell principle is used to obtain a completely analytical two-dimensional spectrum; any frequency domain line-by-line imaging algorithm can be combined with the obtained two-dimensional spectrum, which has universal applicability.

[0145] In an exemplary embodiment, the establishing unit comprises:

[0146] A first determination module is used to determine the relative speed of the transmitting array in the multi-receiving array synthetic aperture sonar relative to the target as the relative movement speed of the platform within the signal transmission and reception pulse width;

[0147] A second determination module is used to determine the echo signal of each receiving array in the multi-receiving array synthetic aperture sonar based on the relative speed;

[0148] The echo signal is demodulated to remove the carrier frequency, thereby obtaining the echo baseband signal.

[0149] In an exemplary embodiment, the determining unit includes:

[0150] A first analysis module, configured to obtain a first analysis result by performing an approximate error analysis on a first error factor, wherein the first error factor affects an envelope delay and a phase of the echo signal;

[0151] A second analysis module, configured to obtain a second analysis result by performing an approximate error analysis on a second error factor, wherein the second error factor affects an envelope delay of the echo signal;

[0152] A third analysis module, configured to obtain a third analysis result by performing an approximate error analysis on a third error factor, wherein the third error factor affects the phase of the echo signal;

[0153] An approximation module is used to obtain the approximate echo baseband signal based on the first analysis result, the second analysis result and the third analysis result.

[0154] In an exemplary embodiment, the solving unit comprises:

[0155] An acquisition module, used for acquiring a range frequency domain signal of the approximate echo baseband signal;

[0156] The third determination module is used to determine the range phase dwell time of the range frequency domain signal according to the phase dwell principle.

[0157] In an exemplary embodiment, the apparatus further comprises:

[0158] A second determining unit, configured to determine the propagation time at the equivalent phase center as the signal propagation time of the approximate echo signal, and determine the distance history of the approximate echo baseband signal;

[0159] The second solving unit is used to solve the two-dimensional spectrum of the approximate echo baseband signal in the approximate signal model based on the distance history.

[0160] In one exemplary embodiment, the imaging comprises:

[0161] A first compensation module, configured to compensate a fixed phase term in a two-dimensional time domain in the two-dimensional spectrum, wherein the fixed phase term is a corresponding first phase multiplication factor;

[0162] A compression module, used for performing distance compression after Fourier transform in the distance frequency domain by means of a second phase multiplication factor;

[0163] The second compensation module is used to perform envelope delay compensation in the distance frequency domain through a third phase multiplication factor.

[0164] In an exemplary embodiment, the apparatus further comprises:

[0165] A reconstruction unit, used for obtaining the azimuth time domain reconstruction result of the two-dimensional spectrum through inverse Fourier transform in the range frequency domain;

[0166] A focusing unit is used to combine the azimuth time domain reconstruction result with a single-station imaging algorithm to obtain the multi-receiving array synthetic aperture sonar imaging result.

[0167] It should be noted here that the examples and scenarios implemented by the above-mentioned modules and corresponding steps are the same, but are not limited to the contents disclosed in the above-mentioned embodiments. It should be noted that the above-mentioned modules as part of the device can run in a hardware environment and can be implemented by software or hardware, wherein the hardware environment includes a network environment.

[0168] According to another aspect of the embodiments of the present application, a storage medium is also provided. Optionally, in this embodiment, the storage medium can be used to execute the program code of any of the multi-receiving array synthetic aperture sonar imaging methods considering intrapulse motion in the embodiments of the present application.

[0169] Optionally, in this embodiment, the storage medium is configured to store program codes for executing the following steps:

[0170] S1, in the case where the relative movement speed of the platform within the width of the signal transmission and reception pulses remains unchanged within a pulse repetition period, an echo baseband signal model in a two-dimensional plane is established;

[0171] S2, performing error analysis on the envelope delay and phase of the echo baseband signal in the echo baseband signal model based on the waveform stretching factor, and determining an approximate signal model of the echo baseband signal model;

[0172] S3, solving the two-dimensional spectrum of the approximate echo baseband signal in the approximate signal model;

[0173] S4, based on the two-dimensional spectrum, uses the single-station imaging algorithm to complete focusing and obtain the multi-receiver array synthetic aperture sonar imaging results.

[0174] Optionally, the specific examples in this embodiment may refer to the examples described in the above embodiments, which will not be described in detail in this embodiment.

[0175] Among them, computer-readable storage media may include, but are not limited to, any type of disk, including floppy disks, optical disks, DVDs, CD-ROMs, microdrives and magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, DRAMs, VRAMs, flash memory devices, magnetic or optical cards, nanosystems (including molecular memory ICs), or any type of medium or device suitable for storing instructions and / or data.

[0176] According to another aspect of an embodiment of the present application, an electronic device for implementing the above-mentioned multi-receiving array synthetic aperture sonar imaging method considering intra-pulse motion is also provided. The electronic device may be a server, a terminal, or a combination thereof.

[0177] Fig. 9 is a schematic diagram of the structure of an optional electronic device according to an embodiment of the present application, such as Fig. 9 As shown, it includes a processor 902, a communication interface 904, a memory 906 and a communication bus 908, wherein the processor 902, the communication interface 904, and the memory 906 communicate with each other through the communication bus 908, wherein:

[0178] Memory 906, used for storing computer programs;

[0179] The processor 902 is used to implement the following steps when executing the computer program stored in the memory 906:

[0180] S1, in the case where the relative movement speed of the platform within the width of the signal transmission and reception pulses remains unchanged within a pulse repetition period, an echo baseband signal model in a two-dimensional plane is established;

[0181] S2, performing error analysis on the time delay and phase of the echo baseband signal in the echo baseband signal model based on the waveform stretching factor, and determining an approximate signal model of the echo baseband signal model;

[0182] S3, solving the two-dimensional spectrum of the approximate echo baseband signal in the approximate signal model;

[0183] S4, based on the two-dimensional spectrum, uses the single-station imaging algorithm to complete focusing and obtain the multi-receiver array synthetic aperture sonar imaging results.

[0184] Optionally, the communication bus may be a PCI (Peripheral Component Interconnect) bus, or an EISA (Extended Industry Standard Architecture) bus, etc. The communication bus may be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Fig. 9 The communication interface is used for communication between the electronic device and other devices.

[0185] The memory may include RAM, or may include non-volatile memory, such as at least one disk memory. Optionally, the memory may also be at least one storage device located away from the aforementioned processor.

[0186] As an example, the memory 906 may include, but is not limited to, the establishing unit 802, the first determining unit 804, the first solving unit 806, and the imaging unit 808 in the multi-receiving array synthetic aperture sonar imaging device considering intra-pulse motion. In addition, other module units in the multi-receiving array synthetic aperture sonar imaging device considering intra-pulse motion may also be included but are not limited to, which will not be described in detail in this example.

[0187] The above-mentioned processor can be a general-purpose processor, which can include but not be limited to: CPU (Central Processing Unit), NP (Network Processor), etc.; it can also be DSP (Digital Signal Processing), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components.

[0188] Optionally, the specific examples in this embodiment may refer to the examples described in the above embodiments, and this embodiment will not be described in detail here.

[0189] It should be noted that, for the aforementioned method embodiments, for the sake of simplicity, they are all expressed as a series of action combinations, but those skilled in the art should be aware that the present application is not limited by the described order of actions, because according to the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present application.

[0190] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0191] In the several embodiments provided in the present application, it should be understood that the disclosed devices can be implemented in other ways. For example, the device embodiments described above are only schematic, such as the division of the units, which is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some service interfaces, and the indirect coupling or communication connection of devices or units can be electrical or other forms.

[0192] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0193] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0194] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable memory. Based on this understanding, the technical solution of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a memory, including a number of instructions to enable a computer device (which can be a personal computer, server or network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned memory includes: U disk, read-only memory (ROM), random access memory (RAM), mobile hard disk, disk or optical disk and other media that can store program code.

[0195] A person of ordinary skill in the art can understand that all or part of the steps in the various methods of the above embodiments can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable memory, which can include: a flash drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, etc.

[0196] The above is only an exemplary embodiment of the present disclosure, and the scope of the present disclosure cannot be limited thereto. That is, any equivalent changes and modifications made according to the teachings of the present disclosure are still within the scope of the present disclosure. After considering the specification and practicing the disclosure here, those skilled in the art will easily think of the implementation scheme of the present disclosure. This application is intended to cover any modification, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary technical means in the technical field not recorded in the present disclosure. The description and examples are regarded as exemplary only, and the scope and spirit of the present disclosure are defined by the claims.

[0197] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0198] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A multi-receive array synthetic aperture sonar imaging method considering intrapulse motion, characterized in that: include: Under the condition that the relative movement speed of the platform within the width of the signal transmission and reception pulses remains unchanged within a pulse repetition period, the echo baseband signal model in the two-dimensional plane is established; Performing error analysis on envelope delay and phase of the echo baseband signal in the echo baseband signal model based on the waveform stretching factor to determine an approximate signal model of the echo baseband signal model; Solving the two-dimensional spectrum of the approximate echo baseband signal in the approximate signal model; Based on the two-dimensional spectrum, a single-station imaging algorithm is used to complete focusing and obtain a multi-receiving array synthetic aperture sonar imaging result.

2. The multi-receiving array synthetic aperture sonar imaging method considering intra-pulse motion as claimed in claim 1, characterized in that: The method of establishing the echo baseband signal model in a two-dimensional plane under the condition that the relative movement speed of the platform within the width of the signal transmission and reception pulses remains unchanged within a pulse repetition period includes: The relative speed of the transmitting array in the multi-receiving array synthetic aperture sonar relative to the target is determined as the relative movement speed of the platform within the width of the signal transmitting and receiving pulses; Determine the echo signal of each receiving array in the multi-receiving array synthetic aperture sonar based on the relative speed; The echo signal is demodulated to remove the carrier frequency, thereby obtaining the echo baseband signal.

3. The multi-receiving array synthetic aperture sonar imaging method considering intra-pulse motion as claimed in claim 1, characterized in that: The determining of the approximate signal model of the echo baseband signal model comprises: Obtaining a first analysis result by performing an approximate error analysis on a first error factor, wherein the first error factor affects an envelope delay and a phase of the echo signal; Obtaining a second analysis result by performing an approximate error analysis on a second error factor, wherein the second error factor affects an envelope delay of the echo signal; Obtaining a third analysis result by performing an approximate error analysis on a third error factor, wherein the third error factor affects the phase of the echo signal; The approximate echo baseband signal is obtained based on the first analysis result, the second analysis result and the third analysis result.

4. The multi-receiving array synthetic aperture sonar imaging method considering intra-pulse motion as claimed in claim 1, characterized in that: The step of solving the two-dimensional spectrum of the approximate echo baseband signal in the approximate signal model comprises: Acquire a range frequency domain signal of the approximate echo baseband signal; According to the phase dwell principle, the range phase dwell time of the range frequency domain signal is determined.

5. The multi-receiving array synthetic aperture sonar imaging method considering intra-pulse motion as claimed in claim 4, characterized in that: After determining the range phase dwell time of the range frequency domain signal, the method further includes: Determine the propagation time at the equivalent phase center as the signal propagation time of the approximate echo signal, and determine the distance history of the approximate echo baseband signal; A two-dimensional spectrum of an approximate echo baseband signal in the approximate signal model is solved based on the distance history.

6. The multi-receiving array synthetic aperture sonar imaging method considering intra-pulse motion as claimed in claim 1, characterized in that: The method of focusing based on the two-dimensional spectrum using a single-station imaging algorithm to obtain a multi-receiving array synthetic aperture sonar imaging result includes: A two-dimensional time domain compensation fixed phase term in the two-dimensional spectrum, wherein the fixed phase term is a corresponding first phase multiplication factor; Range compression is performed after Fourier transformation in the range frequency domain by means of a second phase multiplication factor; Envelope delay compensation is performed in the distance frequency domain via the third phase multiplication factor.

7. The multi-receiving array synthetic aperture sonar imaging method considering intra-pulse motion according to any one of claims 1 to 6, characterized in that: The method further comprises: Obtaining the azimuth time-domain reconstruction result of the two-dimensional spectrum through inverse Fourier transform in the range frequency domain; The multi-receiving array synthetic aperture sonar imaging result is obtained by combining the azimuth time domain reconstruction result with a single-station imaging algorithm.

8. A multi-receiving array synthetic aperture sonar imaging device taking into account intrapulse motion, characterized in that: include: The establishing unit is used to establish the echo baseband signal model in the two-dimensional plane under the condition that the relative movement speed of the platform within the width of the signal transmission and reception pulses remains unchanged within a pulse repetition period; A first determining unit, configured to perform error analysis on an envelope delay and a phase of an echo baseband signal in the echo baseband signal model based on a waveform stretching factor, and determine an approximate signal model of the echo baseband signal model; A first solving unit, used for solving a two-dimensional spectrum of an approximate echo baseband signal in the approximate signal model; The imaging unit is used to complete focusing based on the two-dimensional spectrum using a single-station imaging algorithm to obtain a multi-receiving array synthetic aperture sonar imaging result.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored program, wherein the program executes the method according to any one of claims 1 to 7 when executed.

10. An electronic device comprising a memory and a processor, characterized in that: A computer program is stored in the memory, and the processor is configured to execute the method according to any one of claims 1 to 7 through the computer program.

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