Transmit-receive monostatic synthetic aperture sonar range stack imaging method, system and apparatus

Abstract

The application discloses a kind of transceiver combined synthetic aperture sonar distance stack imaging method, system and device, it is related to image processing technical field, the distance stack imaging method includes steps: for the reference point target in imaging area, the two-way slant range history is calculated;Based on two-way slant range history and the parameter of transmission signal, the reference echo signal of reference point target is calculated, and reference spectrum is obtained by two-dimensional frequency domain transformation;For the original measured echo signal of transceiver combined synthetic aperture sonar, echo spectrum is obtained by two-dimensional frequency domain transformation, and echo spectrum and reference spectrum are conjugated in two-dimensional frequency domain Multiplication;For the coherent accumulation of conjugated multiplication result in distance direction frequency domain, and inverse fourier transform is carried out in azimuth direction;For the pixel at other distances in imaging area, according to the above steps, the processing result of all pixels in entire imaging area is obtained, on the basis, de-loading frequency is carried out, and the imaging result of entire imaging area is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of image processing, in particular to a transmit-receive collocated synthetic aperture sonar range stack imaging method, system and device. BACKGROUND

[0002] The transmit-receive collocated synthetic aperture sonar virtually synthesizes a large aperture array based on a small aperture array moving at a constant speed in a straight line, thereby obtaining constant azimuth resolution independent of detection range and operating frequency; in order to simplify imaging processing, the traditional imaging algorithm generally makes an approximation that the transmit-receive collocated synthetic aperture sonar is stationary during signal transmission and echo reception, which is the so-called "stop-go-stop" approximation. In fact, the sonar cannot remain stationary during signal transmission and echo reception when it is working, but continuously moves at a constant speed in the azimuth direction. That is, the position of the sonar in the azimuth direction when receiving echoes is not the position when transmitting signals, and this position difference will cause changes in the Doppler and range migration of the echoes. If the traditional imaging algorithm based on the "stop-go-stop" approximation model is directly used for imaging processing, the Doppler and range migration errors caused by the position difference of the transmit-receive signal array are not compensated for, and when the imaging distance is far, the imaging result is not accurate enough, and even the imaging result may be distorted. SUMMARY

[0003] In view of the above technical problems, the present application provides a transmit-receive collocated synthetic aperture sonar range stack imaging method for imaging the echoes of a transmit-receive collocated synthetic aperture sonar, the range stack imaging method comprising the following steps:

[0004] S1, for a reference point target with a distance coordinate of and an azimuth coordinate of 0 in the calculation imaging area, accurately calculating the two-way slant range history;

[0005] S2, based on the accurately calculated two-way slant range history and the parameters of the transmitted signal, calculating the reference echo signal of the reference point target in step S1, and performing two-dimensional frequency domain transformation on the reference echo signal to obtain a reference spectrum;

[0006] S3, performing two-dimensional frequency domain transformation on the original measured echo signal of the transmit-receive collocated synthetic aperture sonar to obtain an echo spectrum, and performing a conjugate multiplication operation on the echo spectrum and the reference spectrum in two-dimensional frequency domain;

[0007] S4, for the conjugate multiplication result in step S3, performing a coherent accumulation operation in the range direction and an inverse Fourier transform operation in the azimuth direction;

[0008] S5, the processing steps of step S1, step S2, step S3 and step S4 are performed for other pixels at other distances in the imaging area, and the processing results of all pixels in the imaging area are obtained, and the imaging results of the entire imaging area are obtained after the de-carrier operation.

[0009] Preferably, in step S1, it is assumed that the slow time of the transceiver array synthetic aperture sonar in the azimuth direction is , the coordinate of any pixel in the imaging area in the range direction is , the coordinate of the transceiver array synthetic aperture sonar in the azimuth direction is 0, the towing speed of the transceiver array synthetic aperture sonar is , the coordinate of the transceiver array synthetic aperture sonar in the azimuth direction is , the exact propagation time of the transceiver array synthetic aperture sonar signal from transmission to reception is , the distance of the transceiver array synthetic aperture sonar along the azimuth direction in this time is , the distance between the transceiver array synthetic aperture sonar and the pixel in the imaging area at the signal transmission time is calculated , the expression is , the distance between the transceiver array synthetic aperture sonar and the pixel in the imaging area at the signal reception time is calculated according to the exact propagation time of the transceiver array synthetic aperture sonar signal from transmission to reception , the expression is , and the exact two-way slant range history can be calculated, and the expression is .

[0010] Preferably, in step S2, it is assumed that the transmitted signal is , where is the range direction fast time, and the exact two-way slant range history corresponding time delay is , where represents the sound speed in water, so the reference point target with the range direction coordinate and the azimuth direction coordinate 0 can be represented as . .

[0011] Preferably, in step S3, the original measured echo signal of the transceiver array synthetic aperture sonar is , and the echo spectrum is obtained after two-dimensional frequency domain transformation , , represent the range direction instantaneous frequency and the azimuth direction Doppler frequency respectively, and the expression for the conjugate multiplication operation of the echo spectrum and the reference spectrum in the two-dimensional frequency domain is ​, where * represents the reference spectrum in step S2 The conjugate operation is performed.

[0012] Preferably, in step S4, the coherent accumulation operation is performed in the range-azimuth domain for the conjugate multiplication result in step S3, and the result after the coherent accumulation operation is The expression of the result is: The inverse Fourier transform in the azimuth direction is performed for the result after the coherent accumulation operation , and the processing result of different pixels with the range coordinate value is obtained. The expression of the result is: wherein, represents the coordinate of the target in the azimuth direction, represents the imaginary unit.

[0013] Preferably, in step S5, the processing of steps S1, S2, S3 and S4 is repeated, and in steps S1, S2, S3 and S4, the coordinate of the reference target in the range direction in the imaging area is updated to the corresponding coordinate value to obtain the processing result on the corresponding range coordinate value . For the coordinate values corresponding to all the sampling gates in the range direction, the processing method of steps S1, S2, S3 and S4 is iteratively calculated to obtain the processing result corresponding to the entire imaging area . Based on the result, the de-carrier frequency processing is performed to obtain the final imaging result of the entire imaging area The expression of the result is: , represents the carrier frequency.

[0014] According to another aspect of the present application, the present application provides a transceiver array synthetic aperture sonar range stack imaging system for imaging the echo of a transceiver array synthetic aperture sonar, the range stack imaging system comprising:

[0015] a first calculation unit, wherein the first calculation unit is configured to accurately calculate the two-way slant range history for a reference point target with the range coordinate and the azimuth coordinate 0 in the calculation imaging area;

[0016] a second calculation unit, wherein the second calculation unit is configured to calculate the reference echo signal of the reference point target based on the accurately calculated two-way slant range history and the parameters of the transmitted signal;

[0017] a first transformation unit, wherein the first transformation unit is configured to perform two-dimensional frequency domain transformation on the reference echo signal to obtain a reference spectrum;

[0018] a second transform unit, wherein the second transform unit is configured to perform a two-dimensional frequency domain transform on the raw measured echo signals of the transceiver-compound synthetic aperture sonar to obtain an echo spectrum;

[0019] a conjugate multiplication unit, wherein the conjugate multiplication unit is configured to perform a conjugate multiplication operation on the echo spectrum and the reference spectrum in the two-dimensional frequency domain to obtain a conjugate multiplication result;

[0020] a conjugate multiplication processing unit, wherein the conjugate multiplication processing unit is configured to perform a coherent accumulation operation on the conjugate multiplication result in the range frequency domain and an inverse Fourier transform operation in the azimuth direction;

[0021] an imaging unit, wherein the imaging unit is configured to repeat the first calculation unit, the second calculation unit, the first transform unit, the second transform unit, the conjugate multiplication unit, the conjugate multiplication processing unit for other pixels at different ranges in the imaging region to obtain the processing results of all pixels in the entire imaging region, and then perform a de-chirp operation to obtain the imaging results of the entire imaging region.

[0022] According to another aspect of the present application, the present application further provides a computing device comprising a processor and a memory, wherein computer program instructions are stored in the memory, and the computer program instructions, when executed in the processor, cause the processor to perform the transceiver-compound synthetic aperture sonar range stack imaging method as follows:

[0023] S1, for a reference point target in the imaging region with a range coordinate of and an azimuth coordinate of 0, accurately calculating a two-way slant range history;

[0024] S2, based on the accurately calculated two-way slant range history and the parameters of the transmitted signal, calculating the reference echo signal of the reference point target in step S1, and performing a two-dimensional frequency domain transform on the reference echo signal to obtain a reference spectrum;

[0025] S3, performing a two-dimensional frequency domain transform on the raw measured echo signals of the transceiver-compound synthetic aperture sonar to obtain an echo spectrum, and performing a conjugate multiplication operation on the echo spectrum and the reference spectrum in the two-dimensional frequency domain;

[0026] S4, for the conjugate multiplication result in step S3, performing a coherent accumulation operation in the range frequency domain and an inverse Fourier transform operation in the azimuth direction;

[0027] S5, for other pixels at different ranges in the imaging region, performing the processing steps of steps S1, S2, S3, and S4 to obtain the processing results of all pixels in the entire imaging region, and then performing a de-chirp operation to obtain the imaging results of the entire imaging region.

[0028] Compared with the prior art, the distance stack imaging method has at least the following beneficial effects: compared with the traditional transceiver collocation synthetic aperture sonar imaging method, the distance stack imaging method compensates for the motion along the azimuth direction during the transmission and reception of signals of the transceiver collocation synthetic aperture sonar, so that the targets in the entire imaging area can be completely focused, and the distance stack imaging method can greatly improve the imaging efficiency of the transceiver collocation synthetic aperture sonar. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 A flowchart of a transceiver collocation synthetic aperture sonar distance stack imaging method of a preferred embodiment of the present application.

[0030] Figure 2 A spatial geometry between the transceiver collocation synthetic aperture sonar and the target in the distance stack imaging method of the above-mentioned preferred embodiment of the present application.

[0031] Figure 3 An azimuth profile of the imaging results of the distance stack imaging method of the present application and the traditional distance stack imaging method.

[0032] Figure 4 A local enlarged view of the main lobe of the azimuth profile of the imaging results of the distance stack imaging method of the present application and the traditional distance stack imaging method.

[0033] Figure 5 A framework diagram of a transceiver collocation synthetic aperture sonar distance stack imaging system of a preferred embodiment of the present application.

[0034] Figure 6 A block diagram of a computing device of a preferred embodiment of the present application.

[0035] In the drawings:

[0036] 800, distance stack imaging system; 810, first computing unit; 820, second computing unit; 830, first transformation unit; 840, second transformation unit; 850, conjugate multiplication unit; 860, conjugate multiplication result processing unit; 870, imaging unit;

[0037] 900, computing device; 910, processor; 920, memory; 930, input device; 940, output device. DETAILED DESCRIPTION

[0038] Before any embodiments of the application are explained in detail, it is to be understood that the application is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The application is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising" or "having" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms "mounted," "connected," "supported," and "coupled" and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, "connected" and "coupled" are not restricted to physical or mechanical connections or couplings.

[0039] Also, in the disclosure of the present application, the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore the above terms cannot be understood as limiting the present application; secondly, the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of one element can be one, and in another embodiment, the number of the element can be multiple, and the term "one" cannot be understood as limiting the number.

[0040] Reference will now be made to the drawings accompanying the present application Figure 1 A distance stack imaging method of a transceiver integrated synthetic aperture sonar according to a preferred embodiment of the present application will be disclosed and described in the following description, which specifically includes the following steps: S1, for the distance stack imaging method, the distance stack imaging method is used for calculating the distance stack imaging of the imaging region, and the distance stack imaging method is used for calculating the distance stack imaging of the imaging region S1. For the reference point target with azimuth coordinate 0, accurately calculate the two-way slant range history; S2. Based on the accurately calculated two-way slant range history and the parameters of the transmitted signal, calculate the reference echo signal of the reference point target in step S1, and perform a two-dimensional frequency domain transformation on the reference echo signal to obtain the reference spectrum; S3. Perform a two-dimensional frequency domain transformation on the original measured echo signal of the transceiver synthetic aperture sonar to obtain the echo spectrum, and perform a conjugate multiplication operation on the echo spectrum and the reference spectrum in the two-dimensional frequency domain; S4. For the conjugate multiplication result in step S3, perform a coherent accumulation operation in the range frequency domain, and perform an inverse Fourier transform operation in the azimuth direction; S5. For the pixels at other distances in the imaging area, process them according to the processing steps of steps S1, S2, S3, and S4 to obtain the processing results of all pixels in the entire imaging area. On this basis, perform a carrier frequency removal operation to obtain the imaging result of the entire imaging area. The range stacking imaging method compensates for azimuthal motion during the transmission and reception of signals by the transceiver synthetic aperture sonar, thereby enabling the target to be fully focused throughout the entire imaging area. Furthermore, the range stacking imaging method of this invention can significantly improve the imaging efficiency of transceiver synthetic aperture sonar.

[0041] Figure 2 This is a spatial geometry diagram of the transceiver synthetic aperture sonar and the target in the range stacking imaging method described in this invention. The axis is the distance direction. The axis represents the azimuth direction. The black-filled hexagon represents a pixel in the imaging region along the range direction, with its coordinates being 0 in the azimuth direction and 0 in the range direction. When the combined transceiver synthetic aperture sonar is not in operation, its azimuth coordinate is 0, and its velocity... sports After a certain period of time, the azimuth coordinates of the combined transceiver synthetic aperture sonar are: The precise propagation time of the combined transmit and receive synthetic aperture sonar signal from transmission to reception is... During this time period, the distance traveled by the combined transceiver synthetic aperture sonar along the azimuth direction is... .

[0042] In step S1, for the distance coordinates in the calculated imaging region, In the section "Accurately Calculating the Two-Way Slant Range History for a Reference Point Target with Azimuth Coordinate of 0," it is assumed that the slow time of the combined transceiver synthetic aperture sonar in the azimuth direction is... The coordinates of any pixel in the imaging region in the distance direction are If the azimuth coordinate is 0, then calculate the distance between the transceiver synthetic aperture sonar at the moment of signal transmission and this pixel in the imaging region. The expression is Based on the precise propagation time of the signal from transmission to reception Calculate the distance between the transceiver synthetic aperture sonar and this pixel in the imaging region at the moment of signal reception. The expression is This allows for the calculation of the precise two-way slant distance history. The expression is .

[0043] In step S2, "Based on the precisely calculated two-way slant range history and the parameters of the transmitted signal, calculate the reference echo signal of the reference point target in step S1, and perform a two-dimensional frequency domain transformation on the reference echo signal to obtain the reference spectrum," it is assumed that the transmitted signal is... ,in, To determine the distance travel time, the accurate two-way slant distance history is obtained according to step S1. The corresponding latency is ,in, Representing the speed of sound in water, the distance coordinate is... Echo signal of the reference point target with azimuth coordinate 0 It can be represented as: Among them, the slow time for the azimuth direction is .right Perform a two-dimensional frequency domain transformation to obtain the reference spectrum. , , These represent the instantaneous frequency in the range direction and the Doppler frequency in the azimuth direction, respectively.

[0044] In step S3, "perform a two-dimensional frequency domain transformation on the original measured echo signal of the transceiver synthetic aperture sonar to obtain the echo spectrum, and perform a conjugate multiplication operation between the echo spectrum and the reference spectrum in the two-dimensional frequency domain," it is assumed that the original measured echo signal of the transceiver synthetic aperture sonar is... The echo spectrum is obtained after performing a two-dimensional frequency domain transformation. , , Let represent the instantaneous frequency in the range direction and the Doppler frequency in the azimuth direction, respectively. The echo spectrum and the reference spectrum are multiplied by their conjugates in the two-dimensional frequency domain, and the expression is: Here, * indicates the reference spectrum in step S2. Perform the conjugate operation.

[0045] In step S4, the process of "performing a coherent accumulation operation in the range frequency domain and an inverse Fourier transform operation in the azimuth domain on the conjugate multiplication result from step S3" refers to the result after coherent accumulation. The expression is: ,in, The coordinates of the target in the range direction as defined in step 1. , These represent the instantaneous frequency in the range direction and the Doppler frequency in the azimuth direction, respectively.

[0046] Regarding the results after coherent accumulation Performing an inverse Fourier transform in the azimuth direction yields the range coordinates. Processing results of different pixels Its expression is: ,in, Indicates the target's coordinates in the azimuth direction. This indicates the tow velocity of the combined transmitting and receiving synthetic aperture sonar. It represents the imaginary unit.

[0047] In step S5, "for pixels at other distances in the imaging area, the processing steps of steps S1, S2, S3, and S4 are performed to obtain the processing results of all pixels in the entire imaging area. Based on this, a carrier frequency removal operation is performed to obtain the imaging result of the entire imaging area." Steps S1, S2, S3, and S4 are repeated. During the processing of steps S1, S2, S3, and S4, the coordinates of the reference target in the range direction in the imaging area are updated to the corresponding coordinate values. To obtain the corresponding distance coordinate values The processing results By iteratively calculating the coordinate values ​​corresponding to all sampling gates along the distance according to steps S1, S2, S3, and S4, the processing result corresponding to the entire imaging area is obtained. Based on this result, carrier frequency removal processing is performed to obtain the final imaging result of the entire imaging area. Its expression is: ,in, Indicates distance to fast time. Indicates the carrier frequency.

[0048] Assuming the tow speed of the combined transceiver synthetic aperture sonar (SAPS) is 0.125 m / s, the aperture of its array elements in the azimuth direction is 0.08 m, the center frequency of the transmitted linear frequency modulated (LFM) signal is 150 kHz, the bandwidth is 10 kHz, and the pulse repetition frequency is 6.25 Hz, and assuming an ideal point target exists in the scene with an azimuth aperture coordinate of 10 m and a range spatial coordinate of 111 m, the influence of the SAPS's azimuth motion during signal transmission and reception on the echo is considered. Echo simulation is performed, and based on this, both the traditional range stack imaging method (which does not consider the azimuth motion of the SAPS during signal transmission and reception) and the range stack imaging method described in this invention are used to image the simulated echo. Figure 3An azimuth profile image obtained by imaging processing using a conventional range stacking method and the range stacking imaging method of the present invention, which do not consider the azimuth movement of the combined transceiver synthetic aperture sonar during signal transmission and reception. Figure 4 for Figure 3 A magnified view of a portion of the main lobe. From Figure 4 It can be clearly seen that the imaging results of traditional imaging methods have a small offset in the azimuth direction. This means that traditional imaging methods cannot accurately image the target, resulting in distortion of the focusing result. However, the distance stacking imaging method of the present invention can image the target more accurately without causing distortion of the focusing result, thus verifying that the distance stacking imaging method of the present invention can accurately focus the target within the imaging area.

[0049] Furthermore, comparing the range stack imaging method described in this invention with another transceiver combined synthetic aperture sonar time-domain point-by-point imaging method with better imaging effect, for 800 sampling points in the azimuth direction and 512 sampling points in the range direction, the range stack imaging method of this invention can obtain the imaging result in only 54s, while the time-domain point-by-point imaging method requires 46875s to obtain the imaging result. The range stack imaging method of this invention is about 868 times more efficient than the time-domain point-by-point imaging method, further verifying the high efficiency of the range stack imaging method of this invention.

[0050] Reference Appendix Figure 5 According to another aspect of the present invention, the present invention further provides a range stack imaging method system 800 for transceiver synthetic aperture sonar, used to image the echo of transceiver synthetic aperture sonar. The range stack imaging method system 800 includes a first calculation unit 810, a second calculation unit 820, a first transformation unit 830, a second transformation unit 840, a conjugate multiplication unit 850, a conjugate multiplication result processing unit 860, and an imaging unit 870. The first calculation unit 810, the second calculation unit 820, the first transformation unit 830, the second transformation unit 840, the conjugate multiplication unit 850, the conjugate multiplication result processing unit 860, and the imaging unit 870 cooperate with each other to compensate for the azimuthal motion of the transceiver synthetic aperture sonar during signal transmission and reception, thereby enabling the target within the entire imaging area to be fully focused.

[0051] Specifically, the first calculation unit 810 is used to calculate the range coordinates in the imaging region. The first calculation unit 820 is used to accurately calculate the two-way slant range history of a reference point target with an azimuth coordinate of 0. The second calculation unit 820 is used to calculate the reference echo signal of the reference point target based on the accurately calculated two-way slant range history and the parameters of the transmitted signal. The first transformation unit 830 is used to perform a two-dimensional frequency domain transformation on the reference echo signal to obtain a reference spectrum. The second transformation unit 840 is used to perform a two-dimensional frequency domain transformation on the original measured echo signal of the transceiver synthetic aperture sonar to obtain an echo spectrum. The conjugate multiplication unit 850 is used to perform a conjugate multiplication operation on the echo spectrum and the reference spectrum in the two-dimensional frequency domain to obtain the conjugate multiplication result. The conjugate multiplication result processing unit 860 is used to perform a coherent accumulation operation on the conjugate multiplication result in the range direction frequency domain and an inverse Fourier transform operation in the azimuth direction. The imaging unit 870 is used to repeatedly execute the first calculation unit 810, the second calculation unit 820, the first transformation unit 830, the second transformation unit 840, the conjugate multiplication unit 850, and the conjugate multiplication result processing unit 860 for pixels at other distances in the imaging area, so as to obtain the processing results of all pixels in the entire imaging area, and perform a carrier frequency removal operation on this basis to obtain the imaging result of the entire imaging area.

[0052] The first calculation unit 810 calculates the distance coordinate in the imaging region as follows: When accurately calculating the two-way slant range history for a reference point target with an azimuth coordinate of 0, it is assumed that the slow time of the combined transceiver synthetic aperture sonar in the azimuth direction is... The coordinates of any pixel in the imaging region in the distance direction are If the azimuth coordinate is 0, then calculate the distance between the transceiver synthetic aperture sonar at the moment of signal transmission and this pixel in the imaging region. The expression is Based on the precise propagation time of the signal from transmission to reception Calculate the distance between the transceiver synthetic aperture sonar and this pixel in the imaging region at the moment of signal reception. The expression is Therefore, the accurate two-way slant distance history can be calculated. The expression is .

[0053] When the second calculation unit 820 calculates the reference echo signal of the reference point target based on the accurately calculated two-way slant range history and the parameters of the transmitted signal, it assumes that the transmitted signal is... ,in For distance-to-time, precise two-way slant distance history. The corresponding latency is ,in where c is the sound speed in water, and the range coordinate is , and the bearing coordinate is 0 , can be expressed as , where the slow time in bearing is .

[0054] The first transform unit 830 performs a two-dimensional frequency domain transform on the echo signal of the reference point target with the range coordinate and the bearing coordinate being 0 to obtain a reference spectrum , , , where f r and f b represent the range instantaneous frequency and the bearing Doppler frequency, respectively.

[0055] The second transform unit 840 performs a two-dimensional frequency domain transform on the original measured echo signal of the transceiver array synthetic aperture sonar to obtain an echo spectrum, assuming that the original measured echo signal of the transceiver array synthetic aperture sonar is , and the echo spectrum obtained after the two-dimensional frequency domain transform is , , , where f r and f b represent the range instantaneous frequency and the bearing Doppler frequency, respectively.

[0056] The conjugate multiplication unit 850 performs a conjugate multiplication operation in the two-dimensional frequency domain on the echo spectrum obtained by the second transform unit 840 and the reference spectrum obtained by the first transform unit 830 to obtain a conjugate multiplication result, and the expression of the conjugate multiplication result is , where * represents a conjugate operation on the reference spectrum in step S2.

[0057] The conjugate multiplication result processing unit 860 performs a coherent accumulation operation in the range frequency domain and an inverse Fourier transform operation in the bearing direction on the conjugate multiplication result, and the expression of the result after the coherent accumulation is , where is the coordinate of any pixel in the imaging area defined by the first calculation unit 810 in the range direction, i.e., the coordinate of the target in the range direction, , , where f r and f b represent the range instantaneous frequency and the bearing Doppler frequency, respectively. The conjugate multiplication result processing unit 860 performs an inverse Fourier transform in the bearing direction on the result after the coherent accumulation

[0058] , and the range coordinate value of the result is . processing results of different pixels , whose expression is: , wherein, represents the coordinate of the target in the azimuth direction, represents the towing speed of the Towed Synthetic Aperture Sonar, represents the imaginary unit.

[0059] The imaging unit 870 updates the coordinate of the reference target in the distance direction in the imaging area to the corresponding coordinate value when each processing step of the first calculation unit 810, the second calculation unit 820, the first transformation unit 830, the second transformation unit 840, the conjugate multiplication unit 850, and the conjugate multiplication result processing unit 860 is performed, so as to obtain the processing result on the corresponding distance coordinate value . , and the processing result corresponding to the entire imaging area is obtained by iteratively calculating the coordinate values corresponding to all sampling gate pairs in the distance direction according to the processing steps of the first calculation unit 810, the second calculation unit 820, the first transformation unit 830, the second transformation unit 840, the conjugate multiplication unit 850, and the conjugate multiplication result processing unit 860 . Further, the imaging unit 870 performs the de-chirp processing based on the result, so as to obtain the final imaging result of the entire imaging area , whose expression is: , wherein, represents the fast time in the distance direction, represents the carrier frequency.

[0060] Reference is made to the accompanying drawings Figure 6 According to another aspect of the present application, the present application further provides a computing device 900, wherein the computing device 900 comprises a processor 910 and a memory 920, and computer program instructions are stored in the memory 920, and the computer program instructions make the processor 910 execute the distance stack imaging method when running in the processor 910, wherein the distance stack imaging method comprises the following steps: S1, for calculating the distance coordinate ​, the reference point target with the azimuth coordinate of 0, and the two-way slant range history is calculated accurately; S2, the reference echo signal of the reference point target in step S1 is calculated based on the two-way slant range history calculated accurately and the parameters of the transmitted signal, and the reference echo signal is subjected to two-dimensional frequency domain transformation to obtain a reference spectrum; S3, the original measured echo signal of the transceiver combined synthetic aperture sonar is subjected to two-dimensional frequency domain transformation to obtain an echo spectrum, and the echo spectrum is subjected to a conjugate multiplication operation with the reference spectrum in the two-dimensional frequency domain; S4, the conjugate multiplication result in step S3 is subjected to a coherent accumulation operation in the range domain and an inverse Fourier transform operation in the azimuth direction; S5, the pixels at other ranges in the imaging area are processed according to the processing steps of steps S1, S2, S3 and S4, and the processing result of all the pixels in the entire imaging area is obtained, and on this basis, a de-carrier frequency operation is performed, and the imaging result of the entire imaging area is obtained. The distance stack imaging method compensates for the movement along the azimuth direction during the transmission and reception of the transceiver combined synthetic aperture sonar, and thus the targets in the entire imaging area can be completely focused.

[0061] In one embodiment of the computing device 900 of the present application, the memory 920 can include one or more computer program products that can include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. The volatile memory may, for example, include random access memory (RAM), cache memory, and / or the like. The non-volatile memory may, for example, include read-only memory (ROM), hard disk, flash memory, and / or the like. One or more computer program instructions can be stored on the computer-readable storage media, and the processor 910 can execute the program instructions to implement the functions of the distance stack imaging method of the present application described above.

[0062] In one embodiment of the computing device 900 of the present application, the processor 910 can be a central processing unit (CPU) or other forms of processing units with data processing capabilities and / or instruction execution capabilities, which can execute the program instructions stored on the computer-readable storage media to implement the functions of the distance stack imaging method of the present application described above.

[0063] In one embodiment of the computing device 900 of the present application, the computing device 900 can further include an input device 930 and an output device 940. The input device 930 can be, but is not limited to, a keyboard, a mouse, and the output device 940 can be, but is not limited to, a display, a speaker, a printer. The input device 930 and the output device 940 can be connected to the processor 910 through a bus system.

[0064] Those skilled in the art should understand that the embodiments described above and shown in the drawings are merely for illustrative explanation of the present application, and are not intended to limit the present application. All equivalent embodiments, modifications and improvements within the spirit of the present application should be included in the protection scope of the present application.

Claims

1. A range stack imaging method for transceiver synthetic aperture sonar, used for imaging the echoes of transceiver synthetic aperture sonar, characterized in that, The distance stack imaging method includes the following steps: S1, for calculating the range coordinates in the imaging region, For a reference point target with an azimuth coordinate of 0, accurately calculate the two-way slant distance journey; S2, based on the accurately calculated two-way slant range history and the parameters of the transmitted signal, calculate the reference echo signal of the reference point target in step S1, and perform a two-dimensional frequency domain transformation on the reference echo signal to obtain the reference spectrum. S3, perform a two-dimensional frequency domain transformation on the original measured echo signal of the transceiver synthetic aperture sonar to obtain the echo spectrum, and perform a conjugate multiplication operation between the echo spectrum and the reference spectrum in the two-dimensional frequency domain. S4. For the conjugate multiplication result in step S3, perform coherent accumulation in the frequency domain of the range direction and inverse Fourier transform in the azimuth direction. S5. For pixels at other distances in the imaging area, process them according to the processing steps of S1, S2, S3 and S4 to obtain the processing results of all pixels in the entire imaging area. On this basis, perform a carrier frequency removal operation to obtain the imaging result of the entire imaging area. In step S1, it is assumed that the slow time of the transceiver combined synthetic aperture sonar in the azimuth direction is... The coordinates of any pixel in the imaging region in the distance direction are With the azimuth coordinate at 0, the tow velocity of the combined transceiver synthetic aperture sonar is... The coordinates of the combined transceiver synthetic aperture sonar in the azimuth direction are: The precise propagation time of the combined transmit and receive synthetic aperture sonar signal from transmission to reception is... During this time period, the distance traveled by the combined transceiver synthetic aperture sonar along the azimuth direction is... Calculate the distance between the transceiver synthetic aperture sonar at the moment of signal transmission and this pixel in the imaging region. The expression is Based on the precise propagation time of the signal from transmission to reception Calculate the distance between the transceiver synthetic aperture sonar and this pixel in the imaging region at the moment of signal reception. The expression is This allows for the calculation of the precise two-way slant distance history. The expression is ; In step S2, assume the transmitted signal is ,in For distance-to-time, precise two-way slant distance history. The corresponding latency is ,in To represent the speed of sound in water, the distance coordinate is... Echo signal of the reference point target with azimuth coordinate 0 Represented as: .

2. The transceiver combined synthetic aperture sonar range stack imaging method according to claim 1, characterized in that, In step S3, it is assumed that the original measured echo signal of the combined transceiver synthetic aperture sonar is The echo spectrum is obtained after performing a two-dimensional frequency domain transformation. , , Let represent the instantaneous frequency in the range direction and the Doppler frequency in the azimuth direction, respectively. The echo spectrum and the reference spectrum are multiplied by their conjugates in the two-dimensional frequency domain, and the expression is: Here, * indicates the reference spectrum. Perform the conjugate operation.

3. The transceiver combined synthetic aperture sonar range stack imaging method according to claim 2, characterized in that, In step S4, the conjugate multiplication result from step S3 is coherently accumulated in the range-direction frequency domain. The result after coherent accumulation... The expression is: Regarding the results after coherent accumulation Performing an inverse Fourier transform in the azimuth direction yields the range coordinates. Processing results of different pixels Its expression is: ,in, Indicates the target's coordinates in the azimuth direction. It represents the imaginary unit.

4. The transceiver combined synthetic aperture sonar range stack imaging method according to claim 3, characterized in that, In step S5, the processes of steps S1, S2, S3, and S4 are repeated, and in steps S1, S2, S3, and S4, the coordinates of the reference target in the range direction in the imaging area are updated to the corresponding coordinate values. To obtain the corresponding distance coordinate values The processing results By iteratively calculating the coordinate values ​​corresponding to all sampling gates along the distance according to steps S1, S2, S3, and S4, the processing result corresponding to the entire imaging area is obtained. Based on this result, carrier frequency removal processing is performed to obtain the final imaging result of the entire imaging area. Its expression is: , Indicates the carrier frequency.

5. A transceiver combined synthetic aperture sonar range stack imaging system, used for imaging the echo of a transceiver combined synthetic aperture sonar based on the transceiver combined synthetic aperture sonar range stack imaging method according to claim 1, characterized in that, include: A first calculation unit, wherein the first calculation unit is used to calculate the range coordinates of the imaging region. For a reference point target with an azimuth coordinate of 0, accurately calculate the two-way slant distance journey; A second calculation unit, wherein the second calculation unit is used to calculate the reference echo signal of the reference point target based on the accurately calculated two-way slant range history and the parameters of the transmitted signal; A first transformation unit, wherein the first transformation unit is used to perform a two-dimensional frequency domain transformation on the reference echo signal to obtain a reference spectrum; A second transformation unit, wherein the second transformation unit is used to perform two-dimensional frequency domain transformation on the original measured echo signal of the transceiver combined synthetic aperture sonar to obtain the echo spectrum; A conjugate multiplication unit, wherein the conjugate multiplication unit is used to perform a conjugate multiplication operation between the echo spectrum and the reference spectrum in the two-dimensional frequency domain, and obtain the conjugate multiplication result; A conjugate multiplication processing unit, wherein the conjugate multiplication processing unit is used to perform a coherent accumulation operation on the conjugate multiplication result in the range frequency domain and an inverse Fourier transform operation in the azimuth direction; An imaging unit is provided, wherein the imaging unit is used to repeatedly execute the first calculation unit, the second calculation unit, the first transformation unit, the second transformation unit, the conjugate multiplication unit, and the conjugate multiplication processing unit for pixels at other distances in the imaging region, so as to obtain the processing results of all pixels in the entire imaging region, and perform a carrier frequency removal operation on this basis to obtain the imaging result of the entire imaging region.

6. The transceiver combined synthetic aperture sonar range stack imaging system according to claim 5, characterized in that, The first calculation unit calculates the range coordinates of the imaging region as follows: When accurately calculating the two-way slant range history for a reference point target with an azimuth coordinate of 0, it is assumed that the slow time of the combined transceiver synthetic aperture sonar in the azimuth direction is... The coordinates of any pixel in the imaging region in the distance direction are With the azimuth coordinate at 0, the tow velocity of the combined transceiver synthetic aperture sonar is... Calculate the distance between the transceiver synthetic aperture sonar at the moment of signal transmission and this pixel in the imaging region. The expression is Based on the precise propagation time of the signal from transmission to reception Calculate the distance between the transceiver synthetic aperture sonar and this pixel in the imaging region at the moment of signal reception. The expression is This allows for the calculation of the precise two-way slant distance history. The expression is .

7. The transceiver combined synthetic aperture sonar range stack imaging system according to claim 6, characterized in that, When the second calculation unit calculates the reference echo signal of the reference point target based on the accurately calculated two-way slant range history and the parameters of the transmitted signal, it assumes that the transmitted signal is... ,in, For distance-to-time, precise two-way slant distance history. The corresponding latency is ,in, Representing the speed of sound in water, the distance coordinate is... Echo signal of the reference point target with azimuth coordinate 0 Represented as: .

8. A computing device, characterized in that, It includes a processor and a memory, wherein computer program instructions are stored in the memory, and when the computer program instructions are executed in the processor, the processor causes the processor to perform the transceiver combined synthetic aperture sonar range stack imaging method as described in any one of claims 1 to 4.

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