A near-field phase compensation method based on high-frequency multi-beam sonar

Abstract

The present application relates to a kind of near-field phase compensation methods based on high-frequency multi-beam sonar, the compensation method needs to measure three groups of data, simultaneously utilize the phase data of left, middle, right three angles of sound source measurement sonar, according to near-field geometric model, the phase difference of each channel is calculated;According to angle, segmented compensation is carried out to channel phase, including the following steps: installing sonar and laying sound source;Data acquisition;Calculate channel phase consistency;Segmented phase compensation.The near-field phase compensation method described in the present application only needs to measure three groups of data, does not need to know the accurate direction of sound source, and the requirement of test environment is not high, so it is simple to implement, the amount of calculation is small, and the compensation effect is remarkable.

Description

Technical Field

[0001] This invention relates to the field of high-frequency multibeam sonar signal processing technology, and in particular to a near-field phase compensation method based on high-frequency multibeam sonar. Background Technology

[0002] High-frequency multibeam sonar is a crucial instrument for marine target detection, especially for small targets. It is primarily used for the precise location and classification of near-range targets in the ocean, thus requiring high-resolution acoustic images. However, in practical engineering, the inability to maintain consistent channel phase leads to significant sidelobe fluctuations, main lobe broadening, or distortion after beamforming, affecting acoustic image quality and resulting in unclear imaging. Therefore, phase compensation of the receiving channel is necessary. Current phase compensation methods require measuring multiple sets of data and selecting the optimal set for compensation calculation. This method is complex, computationally intensive, not fast or convenient, and the compensation effect is generally limited. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a near-field phase compensation method based on high-frequency multi-beam sonar. This compensation method requires measuring three sets of data simultaneously, using a sound source to measure phase data at three angles: left, center, and right. The phase difference between each channel is calculated based on a near-field geometric model. The channel phase is then segmented and compensated according to the angle, including the following steps:

[0004] Step S1: Install the sonar and deploy the sound source; install the sonar on a turntable in a pool or lake, immersing it in the water to a certain depth; place the sound source in front of the sonar at close range, ensuring that it is at the same immersion depth as the sonar.

[0005] Step S2: Data Acquisition; The sound source emits a pulse signal, the sonar begins to receive the signal, acquires and saves array element domain data; After saving a set of data, rotate the turntable to position the sound source to the left of the sonar, acquires and saves array element domain data; Then, rotate the turntable to position the sound source to the right of the sonar, acquires and saves array element domain data; Stop the sonar operation and end the measurement.

[0006] Step S3: Calculate channel phase consistency; calculate the phase difference of each channel by processing the saved data;

[0007] Step S4: Segmented phase compensation; the phase consistency of each channel is calculated based on the three sets of data according to step S3 above.

[0008] In one embodiment of the present invention, the sonar in step S1 needs to rotate with the turntable so that the sound source is located at the center of the sonar.

[0009] In one embodiment of the present invention, the phase difference of each channel in step S3 is specifically defined as follows:

[0010] 1) Calculate the phase value of each channel corresponding to the three sets of data using the FFT phase calculation method. Using one channel as a reference, the phase difference of each channel can be calculated.

[0011] 2) Based on the near-field geometric model, such as Figure 2 As shown. Taking the equivalent acoustic center P of the array as the reference element, and setting it as the origin of the coordinate system; x i Let be the distance of the i-th primitive from the equivalent sound center, with the direction to the right of the origin being positive; let r be the distance of the sound source from the equivalent sound center, and let θ be the angle between the source and the sound axis; then the path phase difference of each channel is obtained.

[0012]

[0013] 3) Since the preset azimuth angle and the distance from the sound source to the equivalent sound center of the array in the above formula are imprecise, and their errors are very sensitive to the measurement of phase consistency, the statistical sum of squares and residual Q are used to accurately estimate the azimuth of the sound source:

[0014]

[0015] The minimum value of the above formula is obtained by summing the azimuth and range segments. The corresponding θ0 and r0 are the precise azimuth and range of the sound source. A comparison diagram of the measured phase and the precisely calculated geometric model phase is shown below. Figure 3 As shown;

[0016] 4) Use the azimuth angle θ0 and distance r0 obtained above to correct the phase difference caused by the near-field sound path, that is, subtract the sound path phase difference from the measured phase difference. The difference is the phase consistency of each channel. The result is as follows: Figure 4 As shown.

[0017] Compared with the prior art, the above-mentioned technical solution of the present invention has the following advantages: the near-field phase compensation method of the present invention only requires the measurement of three sets of data, does not require knowing the precise location of the sound source, has low requirements for the test environment, is simple to implement, has a small amount of calculation, and has a significant compensation effect. Attached Figure Description

[0018] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0019] Figure 1 This is a flowchart illustrating the working method of the near-field phase compensation method based on high-frequency multibeam sonar of the present invention.

[0020] Figure 2 This is a diagram of the near-field geometric model described in this invention;

[0021] Figure 3 This is a phase comparison diagram between the measured and geometric models described in this invention;

[0022] Figure 4 This is a compensation curve diagram of the phase consistency of each channel as described in this invention;

[0023] Figure 5 This is a schematic diagram of the uncompensated receiver directionality curve described in this invention;

[0024] Figure 6 This is a schematic diagram of the compensated receiver directionality curve described in this invention. Detailed Implementation

[0025] like Figure 1 As shown, this embodiment provides a near-field phase compensation method based on high-frequency multi-beam sonar. The compensation method requires measuring three sets of data, simultaneously using a sound source to measure phase data at three angles: left, center, and right. The phase difference of each channel is calculated based on a near-field geometric model. Based on the angle, the channel phase is segmented for compensation, including the following steps:

[0026] Step S1: Install the sonar and deploy the sound source; install the sonar on a turntable in a pool or lake, submerging it to a certain depth; place the sound source close to the sonar, ensuring it is at the same submerged depth as the sonar; rotate the turntable to center the sound source on the sonar.

[0027] Step S2: Data Acquisition; The sound source emits a pulse signal, the sonar begins to receive the signal, acquires and saves array element domain data; After saving a set of data, rotate the turntable to position the sound source to the left of the sonar, acquires and saves array element domain data; Then, rotate the turntable to position the sound source to the right of the sonar, acquires and saves array element domain data; Stop the sonar operation and end the measurement.

[0028] Step S3: Calculate channel phase consistency; calculate the phase difference of each channel by processing the saved data;

[0029] Step S4: Segmented phase compensation; the phase consistency of each channel is calculated based on the three sets of data according to step S3 above.

[0030] The channel is divided into three segments, and phase compensation is performed using phase data calculated at the corresponding angles. The receiver directivity before compensation is as follows: Figure 5 As shown, the result after compensation is as follows Figure 6 As shown, it is clear that after phase compensation, the sidelobe undulations are not obvious, the main lobe width is narrowed, and the main lobe is not distorted.

[0031] The phase difference of each channel in step S3 is as follows:

[0032] 1) Calculate the phase value of each channel corresponding to the three sets of data using the FFT phase calculation method. Using one channel as a reference, the phase difference of each channel can be calculated.

[0033] 2) Based on the near-field geometric model, such as Figure 2 As shown. Taking the equivalent acoustic center P of the array as the reference element, and setting it as the origin of the coordinate system; x i Let be the distance of the i-th primitive from the equivalent sound center, with the direction to the right of the origin being positive; let r be the distance of the sound source from the equivalent sound center, and let θ be the angle between the source and the sound axis; then the path phase difference of each channel is obtained.

[0034]

[0035] 3) Since the preset azimuth angle and the distance from the sound source to the equivalent sound center of the array in the above formula are imprecise, and their errors are very sensitive to the measurement of phase consistency, the statistical sum of squares and residual Q are used to accurately estimate the azimuth of the sound source:

[0036]

[0037] The minimum value of the above formula is obtained by summing the azimuth and range segments. The corresponding θ0 and r0 are the precise azimuth and range of the sound source. A comparison diagram of the measured phase and the precisely calculated geometric model phase is shown below. Figure 3 As shown;

[0038] 4) Use the azimuth angle θ0 and distance r0 obtained above to correct the phase difference caused by the near-field sound path, that is, subtract the sound path phase difference from the measured phase difference. The difference is the phase consistency of each channel. The result is as follows: Figure 4 As shown.

[0039] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A near-field phase compensation method based on high-frequency multi-beam sonar, wherein the compensation method requires measuring three sets of data, simultaneously measuring phase data at three angles (left, center, and right) using a sound source, calculating the phase difference of each channel based on a near-field geometric model, and performing segmented compensation of the channel phase according to the angle, characterized in that... Includes the following steps: Step S1: Install the sonar and deploy the sound source; install the sonar on a turntable in a pool or lake, immersing it in the water to a certain depth; place the sound source in front of the sonar at close range, ensuring that it is at the same immersion depth as the sonar. Step S2: Collect data; The sound source emits a pulse signal, and the sonar begins to receive the signal, collecting and saving data in the array element domain. After saving a set of data, the turntable is rotated to position the sound source to the left of the sonar, collecting and saving data in the array element domain. Next, rotate the turntable to position the sound source to the right of the sonar, collect and save the array element domain data; stop the sonar operation and end the measurement. Step S3: Calculate channel phase consistency; calculate the phase difference of each channel by processing the saved data; Specifically, it includes the following sub-steps: The phase values ​​of each channel corresponding to the three sets of data are obtained by using FFT to calculate the phase. Taking one of the channels as a reference, the phase difference of each channel can be calculated. Based on the near-field geometric model, the equivalent acoustic center P of the array is taken as the reference element and set as the origin of the coordinate system. For the first The distance of each element from the equivalent sound center is positive when it is located to the right of the origin; the distance of the sound source from the equivalent sound center is... The angle between the direction of the acoustic axis and the direction of the acoustic axis is ; The path phase difference of each channel is obtained as follows: ; Since the preset azimuth angle and distance from the sound source to the equivalent sound center of the array in the above formula are imprecise, and their errors are very sensitive to the measurement of phase consistency, the statistical sum of squares residuals are used instead. To accurately estimate the location of the sound source: Sum the directions and distances piecewise, find the minimum value of the above formula, and the corresponding... and It refers to the precise azimuth and distance of the sound source; The azimuth angle obtained above and distance To correct for the phase difference caused by the near-field sound path, the sound path phase difference is subtracted from the measured phase difference; the difference is the phase consistency of each channel. ; Step S4: Segmented phase compensation; the phase consistency of each channel is calculated based on the three sets of data according to step S3 above.

2. The near-field phase compensation method according to claim 1, characterized in that: In step S1, the sonar needs to rotate with the turntable so that the sound source is located at the center of the sonar.

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