阅读说明：本技术 非线性声纳最小可检测信噪比测试方法及系统 (Method and system for testing minimum detectable signal-to-noise ratio of nonlinear sonar ) 是由 姚新 胡健辉 董浩 郜扬文 赵海旭 于 2021-08-11 设计创作，主要内容包括：本发明提供了一种非线性声纳最小可检测信噪比测试方法及系统,包括：基于差频信号等效声源级测量实验设备,实测差频等效声源级SL-(差)；采集并记录0°波束差频信号时域波形S-(差)(t)；基于最小可检测信噪比测试实验设备,记录经滤波后的差频信号电压有效值V-(rms)；计算传播损失TL；发射基阵停止发射,标准信号源输出差频信号时域波形S-(差)(t),经功率放大器、标准声源后发射,发射周期为T2,以大于预设声纳作用距离指标且离预设的声纳作用距离指标最近的目标为参考对象,由大到小调整标准信号源输出的差频信号S-(差)(t)的电压有效值,当声纳图像上参考对象消失时,记录标准信号源输出的差频信号电压有效值V2-(rms)；记录背景噪声带内噪声谱级NL；计算最小可检测信噪比。(The invention provides a method and a system for testing the minimum detectable signal-to-noise ratio of nonlinear sonar, comprising the following steps: based on difference frequency signal equivalent sound source level measurement experimental equipment, difference frequency equivalent sound source level SL is actually measured Difference (D) (ii) a Acquiring and recording 0-degree wave beam difference frequency signal time domain waveform S Difference (D) (t); based on the test experiment equipment of the minimum detectable signal-to-noise ratio, the effective value V of the voltage of the filtered difference frequency signal is recorded rms (ii) a Calculating propagation loss TL; the transmitting array stops transmitting, and the standard signal source outputs the time domain waveform S of the difference frequency signal Difference (D) (T) transmitting the signal after passing through a power amplifier and a standard sound source, wherein the transmission period is T2, and adjusting the difference frequency signal S output by the standard signal source from large to small by taking a target which is larger than the preset sonar working distance index and is closest to the preset sonar working distance index as a reference object Difference (D) (t) recording the effective voltage value V2 of the difference frequency signal output by the standard signal source when the reference object disappears on the sonar image rms (ii) a Recording the noise spectrum level NL in the background noise band; calculating a minimum detectable signal-to-noise ratio。)

1. A non-linear sonar minimum detectable signal-to-noise ratio testing method is characterized by comprising the following steps:

step S1: based on the difference frequency signal equivalent sound source level measurement experimental equipment,when the nonlinear sonar normally works, the difference frequency equivalent sound source level SL is actually measured_{Difference (D)}；

Step S2: when the nonlinear sonar normally works, 0-degree wave beam difference frequency signal time domain waveform S is collected and recorded_{Difference (D)}(t)；

Step S3: based on the minimum detectable signal-to-noise ratio test experimental equipment, the transmitting array transmits original frequency signals with the transmitting period of T1, the standard hydrophone receives difference frequency signals, and the voltage effective value V of the filtered difference frequency signals is recorded_rms；

Step S4: according to the effective voltage value V of the filtered difference frequency signal_rmsActually measured difference frequency equivalent sound level SL_{Difference (D)}And standard hydrophone sensitivity M, calculating propagation loss TL;

step S5: the transmitting array stops transmitting, and the standard signal source outputs the time domain waveform S of the difference frequency signal_{Difference (D)}(T) after the sonar signals pass through the power amplifier and the standard sound source, the transmitting period is T2, the transmitting period T2 is less than T1 and meets the preset condition, equidistant targets appear in the 0-degree beam direction of the sonar image, the target which is greater than the preset sonar action distance index and is closest to the preset sonar action distance index is taken as a reference object, and the difference frequency signal S output by the standard signal source is adjusted from large to small_{Difference (D)}(t) recording the effective voltage value V2 of the difference frequency signal output by the standard signal source when the reference object disappears on the sonar image_rmsThe sound source level of the difference frequency signal emitted by the current standard sound source is the minimum detectable sound source level SL₁；

Step S6: stopping transmitting the standard sound source, analyzing the background noise of the receiving array, and recording the noise spectrum level NL in the background noise band;

step S7: SL according to minimum detectable Source level₁Calculating a minimum detectable signal-to-noise ratio by using the background noise in-band noise spectrum level NL and the propagation loss;

the difference frequency signal equivalent sound source level measurement experimental equipment comprises a transmitter and a transmitting array for transmitting an original frequency signal, a standard hydrophone for receiving the difference frequency signal, a standard filter and a standard oscilloscope;

the minimum detectable signal-to-noise ratio test experimental apparatus comprises: calculating propagation loss by using a transmitter for transmitting an original frequency signal, a transmitting array, a standard hydrophone for receiving a difference frequency signal, a standard filter and a standard oscilloscope; the method comprises the steps of utilizing a programmable signal source for transmitting a difference frequency signal, a standard power amplifier and a standard sound source, a receiving array for receiving the difference frequency signal, a receiving electronic cabin, a signal processor for detecting a target of the difference frequency signal and a display and control console for displaying the target to calculate the minimum detectable signal-to-noise ratio.

2. The non-linear sonar minimum detectable signal-to-noise ratio testing method of claim 1, wherein the difference frequency signal equivalent sound source level measurement experimental apparatus employs: a standard hydrophone is arranged right below the auxiliary ship and at a distance H from the underwater depth, the horizontal distance between the standard hydrophone and the transmitting array is D1, and the transmitting array is arranged at the underwater depth H; the distance D1 is greater than the original frequency far-field distance, the original frequency far-field distance is greater than the difference frequency far-field distance, and the distance D1 is not less than the equivalent end-fire array length of the nonlinear sonar nonlinear effect; the depth H is larger than the cavitation depth of the emission signal of the emission array, and the emission array rain standard hydrophones are aligned with the depth and the center of a 0-degree wave beam.

3. The non-linear sonar minimum detectable signal-to-noise ratio test method of claim 1, wherein the measured difference frequency equivalent generator stage SL_{Difference (D)}The method comprises the following steps:

SL_{difference (D)}＝20lg(V1_rms)+20lg(D₁)-M (1)

Wherein M represents the standard hydrophone sensitivity; v1_rmsThe effective value of the signal voltage of the difference frequency sound signal after being received by the standard hydrophone and the filter is shown, and D1 shows the horizontal spacing of the emission matrix rain standard hydrophone.

4. The non-linear sonar minimum detectable signal-to-noise ratio testing method of claim 1, wherein the minimum detectable signal-to-noise ratio testing experimental apparatus employs: adjusting the horizontal distance between a standard hydrophone and an emission matrix in the difference frequency signal equivalent sound source level measurement experimental equipment to be a distance D2, and arranging a standard sound source right below the standard hydrophone; a receiving array is arranged right below the transmitting array; the distance D2 is greater than the difference frequency far-field distance and greater than the equivalent end-fire array length of the nonlinear sonar nonlinear effect; the depth H is larger than the cavitation depth of the transmitting signal of the transmitting array, the transmitting array is aligned with the same depth of the standard hydrophone and the center of the 0-degree wave beam, and the receiving array is aligned with the same depth of the standard sound source and the center of the 0-degree wave beam.

5. The non-linear sonar minimum detectable signal-to-noise ratio test method of claim 1, wherein the propagation loss TL employs:

TL＝SL_{difference (D)}-20lg(V_rms)+M (2)。

6. The non-linear sonar minimum detectable signal-to-noise ratio test method according to claim 1, wherein the step S5 employs:

SL₁＝SL_{difference (D)}+20lg(V2_rms/V1_rms) (3)。

7. The non-linear sonar minimum detectable signal-to-noise ratio test method of claim 1, wherein the minimum detectable signal-to-noise ratio employs:

SE＝SL₁-NL-TL (4)。

8. a non-linear sonar minimum detectable signal-to-noise ratio test system, comprising:

module M1: based on difference frequency signal equivalent sound source level measurement experimental equipment, when the nonlinear sonar normally works, difference frequency equivalent sound source level SL is actually measured_{Difference (D)}；

Module M2: when the nonlinear sonar normally works, 0-degree wave beam difference frequency signal time domain waveform S is collected and recorded_{Difference (D)}(t)；

Module M3: based on the test experimental equipment with the minimum detectable signal-to-noise ratio, the transmitting array transmits original frequency signals with the transmitting period of T1, the standard hydrophones receive difference frequency signals, and the voltage of the filtered difference frequency signals is recordedEffective value V_rms；

Module M4: according to the effective voltage value V of the filtered difference frequency signal_rmsActually measured difference frequency equivalent sound level SL_{Difference (D)}And standard hydrophone sensitivity M, calculating propagation loss TL;

module M5: the transmitting array stops transmitting, and the standard signal source outputs the time domain waveform S of the difference frequency signal_{Difference (D)}(T) after the sonar signals pass through the power amplifier and the standard sound source, the transmitting period is T2, the transmitting period T2 is less than T1 and meets the preset condition, equidistant targets appear in the 0-degree beam direction of the sonar image, the target which is greater than the preset sonar action distance index and is closest to the preset sonar action distance index is taken as a reference object, and the difference frequency signal S output by the standard signal source is adjusted from large to small_{Difference (D)}(t) recording the effective voltage value V2 of the difference frequency signal output by the standard signal source when the reference object disappears on the sonar image_rmsThe sound source level of the difference frequency signal emitted by the current standard sound source is the minimum detectable sound source level SL₁；

Module M6: stopping transmitting the standard sound source, analyzing the background noise of the receiving array, and recording the noise spectrum level NL in the background noise band;

module M7: SL according to minimum detectable Source level₁Calculating a minimum detectable signal-to-noise ratio by using the background noise in-band noise spectrum level NL and the propagation loss;

the difference frequency signal equivalent sound source level measurement experimental equipment comprises a transmitter and a transmitting array for transmitting an original frequency signal, a standard hydrophone for receiving the difference frequency signal, a standard filter and a standard oscilloscope;

the minimum detectable signal-to-noise ratio test experimental apparatus comprises: calculating propagation loss by using a transmitter for transmitting an original frequency signal, a transmitting array, a standard hydrophone for receiving a difference frequency signal, a standard filter and a standard oscilloscope; the method comprises the steps of utilizing a programmable signal source for transmitting a difference frequency signal, a standard power amplifier and a standard sound source, a receiving array for receiving the difference frequency signal, a receiving electronic cabin, a signal processor for detecting a target of the difference frequency signal and a display and control console for displaying the target to calculate the minimum detectable signal-to-noise ratio.

9. The non-linear sonar minimum detectable signal-to-noise ratio testing system of claim 8, wherein the difference frequency signal equivalent source level measurement experiment apparatus employs: a standard hydrophone is arranged right below the auxiliary ship and at a distance H from the underwater depth, the horizontal distance between the standard hydrophone and the transmitting array is D1, and the transmitting array is arranged at the underwater depth H; the distance D1 is greater than the original frequency far-field distance, the original frequency far-field distance is greater than the difference frequency far-field distance, and the distance D1 is not less than the equivalent end-fire array length of the nonlinear sonar nonlinear effect; the depth H is greater than the cavitation depth of the emission signal of the emission array, and the emission array rain standard hydrophones are at the same depth and are aligned with the beam center of 0 degree;

the actually measured difference frequency equivalent source stage SL_{Difference (D)}The method comprises the following steps:

SL_{difference (D)}＝20lg(V1_rms)+20lg(D₁)-M (1)

Wherein M represents the standard hydrophone sensitivity; v1_rmsThe effective value of the signal voltage of the difference frequency sound signal after being received by the standard hydrophone and the filter is shown, and D1 shows the horizontal spacing of the emission matrix rain standard hydrophone.

10. The non-linear sonar minimum detectable signal-to-noise ratio testing system of claim 8, wherein the minimum detectable signal-to-noise ratio testing experiment device employs: adjusting the horizontal distance between a standard hydrophone and an emission matrix in the difference frequency signal equivalent sound source level measurement experimental equipment to be a distance D2, and arranging a standard sound source right below the standard hydrophone; a receiving array is arranged right below the transmitting array; the distance D2 is greater than the difference frequency far-field distance and greater than the equivalent end-fire array length of the nonlinear sonar nonlinear effect; the depth H is greater than the cavitation depth of the transmitting signal of the transmitting array, the transmitting array is at the same depth as the standard hydrophone and is aligned with the center of a 0-degree wave beam, and the receiving array is at the same depth as the standard sound source and is aligned with the center of a 0-degree wave beam;

the propagation loss TL employs:

TL＝SL_{difference (D)}-20lg(V_rms)+M (2)

The module M5 employs:

SL₁＝SL_{difference (D)}+20lg(V2_rms/V1_rms) (3)

The minimum detectable signal-to-noise ratio employs:

SE＝SL₁-NL-TL (4)。

Technical Field

The invention relates to the field of nonlinear sonar performance testing methods, in particular to a method and a system for testing a minimum detectable signal-to-noise ratio of nonlinear sonar.

Background

The nonlinear sonar (particularly sonar using a parametric transmission technology, nonparametric receiving) has the characteristics of low-frequency narrow beam and no side lobe, has the characteristics of long acting distance, suitability for turbid water areas and use in shallow complicated sea areas, and has been effectively applied to the fields of underwater small target detection, seabed shallow stratum detection and underwater self-guiding.

Patent document CN105891805B (application number: 201610327756.6) discloses a method for evaluating sonar detection performance under different environmental noise conditions. And testing the propagation loss of each frequency of the sea area under the test depth in a good hydrological environment and a standard propagation loss database under the good hydrological condition and the low-noise environment with the background changing along with the distance to obtain the relation between the propagation loss and the detection distance. If the standard propagation loss database of the sea area is not established, the database needs to be established first for table look-up in comparison. The invention can solve the problem that the sonar detection performance evaluation depends on the environment noise environment too much, changes the defect that the sonar detection performance index can be evaluated only in a good hydrological environment, and can save a large amount of time and resources and improve the working efficiency. The sonar detection performance evaluation results have unified evaluation results, and can be compared and analyzed, so that reliable basis is provided for judging the quality of sonar performance.

In the field of sonar performance test, in order to reduce the requirements on test sites, environments and equipment and improve test efficiency, a sonar minimum detectable signal-to-noise ratio is usually used for reflecting the sonar operating distance. The actual working signal of the conventional system sonar is ideal, the difference with the standard signal is basically negligible, and the minimum detectable signal-to-noise ratio can be accurately measured by the method for adjusting the size of the standard signal emitted by the standard sound source through actual measurement propagation loss, so that the judgment is carried outThe satisfaction of the sonar range index is shown in fig. 1 (distance D is greater than far field distance). However, the transmitting system of the nonlinear sonar is very complex, and the actual working signal and the standard signal have larger difference, and the energy loss formed by the difference can cause larger error in the process of measuring the minimum detectable signal-to-noise ratio, so that the measured value of the minimum detectable signal-to-noise ratio is better than the true capability of the sonar, thereby reducing the requirement on the acting distance of the sonar. The energy loss due to these differences mainly includes the emission loss E caused by the in-band non-uniformity of the emission system_n1Conversion area loss E caused by insufficient length of end-fire array equivalent to nonlinear effect_n2Conversion rate loss E caused by different frequency down-shift ratios of nonlinear effects_n3And some minor other losses E_nAnd others.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a method and a system for testing the minimum detectable signal-to-noise ratio of nonlinear sonar.

The invention provides a non-linear sonar minimum detectable signal-to-noise ratio testing method, which comprises the following steps:

step S1: based on difference frequency signal equivalent sound source level measurement experimental equipment, when the nonlinear sonar normally works, difference frequency equivalent sound source level SL is actually measured_{Difference (D)}；

Step S2: when the nonlinear sonar normally works, 0-degree wave beam difference frequency signal time domain waveform S is collected and recorded_{Difference (D)}(t)；

Step S3: based on the minimum detectable signal-to-noise ratio test experimental equipment, the transmitting array transmits original frequency signals with the transmitting period of T1, the standard hydrophone receives difference frequency signals, and the voltage effective value V of the filtered difference frequency signals is recorded_rms；

Step S4: according to the effective voltage value V of the filtered difference frequency signal_rmsActually measured difference frequency equivalent sound level SL_{Difference (D)}And standard hydrophone sensitivity M, calculating propagation loss TL;

step S5: the transmitting array stops transmitting, and the standard signal source outputs the time domain waveform S of the difference frequency signal_{Difference (D)}(t) passing through a power amplifier, a standard sound sourceAnd post-transmitting, wherein the transmission period is T2, the transmission period T2 is less than T1 and meets the preset condition, equidistant targets appear in the sonar image beam direction of 0 degree, the target which is greater than the preset sonar action distance index and is closest to the preset sonar action distance index is taken as a reference object, and the difference frequency signal S output by the standard signal source is adjusted from large to small_{Difference (D)}(t) recording the effective voltage value V2 of the difference frequency signal output by the standard signal source when the reference object disappears on the sonar image_rmsThe sound source level of the difference frequency signal emitted by the current standard sound source is the minimum detectable sound source level SL₁；

Step S6: stopping transmitting the standard sound source, analyzing the background noise of the receiving array, and recording the noise spectrum level NL in the background noise band;

step S7: SL according to minimum detectable Source level₁Calculating a minimum detectable signal-to-noise ratio by using the background noise in-band noise spectrum level NL and the propagation loss;

the difference frequency signal equivalent sound source level measurement experimental equipment comprises a transmitter and a transmitting array for transmitting an original frequency signal, a standard hydrophone for receiving the difference frequency signal, a standard filter and a standard oscilloscope;

the minimum detectable signal-to-noise ratio test experimental apparatus comprises: calculating propagation loss by using a transmitter for transmitting an original frequency signal, a transmitting array, a standard hydrophone for receiving a difference frequency signal, a standard filter and a standard oscilloscope; the method comprises the steps of utilizing a programmable signal source for transmitting a difference frequency signal, a standard power amplifier and a standard sound source, a receiving array for receiving the difference frequency signal, a receiving electronic cabin, a signal processor for detecting a target of the difference frequency signal and a display and control console for displaying the target to calculate the minimum detectable signal-to-noise ratio.

Preferably, the difference frequency signal equivalent sound source level measurement experimental equipment adopts: a standard hydrophone is arranged right below the auxiliary ship and at a distance H from the underwater depth, the horizontal distance between the standard hydrophone and the transmitting array is D1, and the transmitting array is arranged at the underwater depth H; the distance D1 is greater than the original frequency far-field distance, the original frequency far-field distance is greater than the difference frequency far-field distance, and the distance D1 is not less than the equivalent end-fire array length of the nonlinear sonar nonlinear effect; the depth H is larger than the cavitation depth of the emission signal of the emission array, and the emission array rain standard hydrophones are aligned with the depth and the center of a 0-degree wave beam.

Preferably, the measured difference frequency equivalent source stage SL_{Difference (D)}The method comprises the following steps:

SL_{difference (D)}＝20lg(V1_rms)+20lg(D₁)-M (1)

Wherein M represents the standard hydrophone sensitivity; v1_rmsThe effective value of the signal voltage of the difference frequency sound signal after being received by the standard hydrophone and the filter is shown, and D1 shows the horizontal spacing of the emission matrix rain standard hydrophone.

Preferably, the minimum detectable signal-to-noise ratio test experimental apparatus employs: adjusting the horizontal distance between a standard hydrophone and an emission matrix in the difference frequency signal equivalent sound source level measurement experimental equipment to be a distance D2, and arranging a standard sound source right below the standard hydrophone; a receiving array is arranged right below the transmitting array; the distance D2 is greater than the difference frequency far-field distance and greater than the equivalent end-fire array length of the nonlinear sonar nonlinear effect; the depth H is larger than the cavitation depth of the transmitting signal of the transmitting array, the transmitting array is aligned with the same depth of the standard hydrophone and the center of the 0-degree wave beam, and the receiving array is aligned with the same depth of the standard sound source and the center of the 0-degree wave beam.

Preferably, the propagation loss TL employs:

TL＝SL_{difference (D)}-20lg(V_rms)+M (2)。

Preferably, the step S5 adopts:

SL₁＝SL_{difference (D)}+20lg(V2_rms/V1_rms) (3)。

Preferably, the minimum detectable signal-to-noise ratio employs:

SE＝SL₁-NL-TL (4)。

the invention provides a non-linear sonar minimum detectable signal-to-noise ratio testing system, which comprises:

module M1: based on difference frequency signal equivalent sound source level measurement experimental equipment, when the nonlinear sonar normally works, difference frequency equivalent sound source level SL is actually measured_{Difference (D)}；

Module M2: in thatWhen the nonlinear sonar normally works, 0-degree wave beam difference frequency signal time domain waveform S is collected and recorded_{Difference (D)}(t)；

Module M3: based on the minimum detectable signal-to-noise ratio test experimental equipment, the transmitting array transmits original frequency signals with the transmitting period of T1, the standard hydrophone receives difference frequency signals, and the voltage effective value V of the filtered difference frequency signals is recorded_rms；

Module M4: according to the effective voltage value V of the filtered difference frequency signal_rmsActually measured difference frequency equivalent sound level SL_{Difference (D)}And standard hydrophone sensitivity M, calculating propagation loss TL;

module M5: the transmitting array stops transmitting, and the standard signal source outputs the time domain waveform S of the difference frequency signal_{Difference (D)}(T) after the sonar signals pass through the power amplifier and the standard sound source, the transmitting period is T2, the transmitting period T2 is less than T1 and meets the preset condition, equidistant targets appear in the 0-degree beam direction of the sonar image, the target which is greater than the preset sonar action distance index and is closest to the preset sonar action distance index is taken as a reference object, and the difference frequency signal S output by the standard signal source is adjusted from large to small_{Difference (D)}(t) recording the effective voltage value V2 of the difference frequency signal output by the standard signal source when the reference object disappears on the sonar image_rmsThe sound source level of the difference frequency signal emitted by the current standard sound source is the minimum detectable sound source level SL₁；

Module M6: stopping transmitting the standard sound source, analyzing the background noise of the receiving array, and recording the noise spectrum level NL in the background noise band;

module M7: SL according to minimum detectable Source level₁Calculating a minimum detectable signal-to-noise ratio by using the background noise in-band noise spectrum level NL and the propagation loss;

the difference frequency signal equivalent sound source level measurement experimental equipment comprises a transmitter and a transmitting array for transmitting an original frequency signal, a standard hydrophone for receiving the difference frequency signal, a standard filter and a standard oscilloscope;

the minimum detectable signal-to-noise ratio test experimental apparatus comprises: calculating propagation loss by using a transmitter for transmitting an original frequency signal, a transmitting array, a standard hydrophone for receiving a difference frequency signal, a standard filter and a standard oscilloscope; the method comprises the steps of utilizing a programmable signal source for transmitting a difference frequency signal, a standard power amplifier and a standard sound source, a receiving array for receiving the difference frequency signal, a receiving electronic cabin, a signal processor for detecting a target of the difference frequency signal and a display and control console for displaying the target to calculate the minimum detectable signal-to-noise ratio.

Preferably, the difference frequency signal equivalent sound source level measurement experimental equipment adopts: a standard hydrophone is arranged right below the auxiliary ship and at a distance H from the underwater depth, the horizontal distance between the standard hydrophone and the transmitting array is D1, and the transmitting array is arranged at the underwater depth H; the distance D1 is greater than the original frequency far-field distance, the original frequency far-field distance is greater than the difference frequency far-field distance, and the distance D1 is not less than the equivalent end-fire array length of the nonlinear sonar nonlinear effect; the depth H is greater than the cavitation depth of the emission signal of the emission array, and the emission array rain standard hydrophones are at the same depth and are aligned with the beam center of 0 degree;

the actually measured difference frequency equivalent source stage SL_{Difference (D)}The method comprises the following steps:

SL_{difference (D)}＝20lg(V1_rms)+20lg(D₁)-M (1)

Wherein M represents the standard hydrophone sensitivity; v1_rmsThe effective value of the signal voltage of the difference frequency sound signal after being received by the standard hydrophone and the filter is shown, and D1 shows the horizontal spacing of the emission matrix rain standard hydrophone.

Preferably, the minimum detectable signal-to-noise ratio test experimental apparatus employs: adjusting the horizontal distance between a standard hydrophone and an emission matrix in the difference frequency signal equivalent sound source level measurement experimental equipment to be a distance D2, and arranging a standard sound source right below the standard hydrophone; a receiving array is arranged right below the transmitting array; the distance D2 is greater than the difference frequency far-field distance and greater than the equivalent end-fire array length of the nonlinear sonar nonlinear effect; the depth H is greater than the cavitation depth of the transmitting signal of the transmitting array, the transmitting array is at the same depth as the standard hydrophone and is aligned with the center of a 0-degree wave beam, and the receiving array is at the same depth as the standard sound source and is aligned with the center of a 0-degree wave beam;

the propagation loss TL employs:

TL＝SL_{difference (D)}-20lg(V_rms)+M (2)

The module M5 employs:

SL₁＝SL_{difference (D)}+20lg(V2_rms/V1_rms) (3)

The minimum detectable signal-to-noise ratio employs:

SE＝SL₁-NL-TL (4)。

compared with the prior art, the invention has the following beneficial effects:

1. compared with the conventional system sonar minimum detectable signal-to-noise ratio test method, the method takes the error caused by the larger difference between the actual working signal and the standard signal into consideration, and the test result is more accurate;

2. compared with the action distance test method, the invention does not need to consider the factors of reverberation, hydrology, target and the like, thereby greatly simplifying the sonar action distance index verification method;

3. the invention has simple test equipment and strong test method operability, improves the test efficiency and reduces the test cost.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:

fig. 1 is a schematic diagram of a minimum detectable signal-to-noise ratio measurement of a conventional system sonar.

Fig. 2 is a schematic diagram of the equivalent sound source level measurement of the nonlinear sonar difference frequency signal of the present invention.

Fig. 3 is a schematic diagram of the minimum detectable signal-to-noise ratio measurement of the nonlinear sonar of the present invention.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.

Example 1

The invention solves the problem that the existing method is difficult to accurately measure the minimum detectable signal-to-noise ratio of the nonlinear sonar; a non-linear sonar minimum detectable signal-to-noise ratio test method is provided.

The invention provides a non-linear sonar minimum detectable signal-to-noise ratio testing method, which comprises the following steps:

step S1: based on difference frequency signal equivalent sound source level measurement experimental equipment, when the nonlinear sonar normally works, difference frequency equivalent sound source level SL is actually measured_{Difference (D)}；

Step S2: when the nonlinear sonar normally works, 0-degree wave beam difference frequency signal time domain waveform S is collected and recorded_{Difference (D)}(t)；

Step S3: based on the minimum detectable signal-to-noise ratio test experimental equipment, the transmitting array transmits original frequency signals with the transmitting period of T1, the standard hydrophone receives difference frequency signals, and the voltage effective value V of the filtered difference frequency signals is recorded_rms；

Step S4: according to the effective voltage value V of the filtered difference frequency signal_rmsActually measured difference frequency equivalent sound level SL_{Difference (D)}And standard hydrophone sensitivity M, calculating propagation loss TL;

step S5: the transmitting array stops transmitting, and the standard signal source outputs the time domain waveform S of the difference frequency signal_{Difference (D)}(t) (where standard signals are not applicable, avoid E_n1、E_n2、E_n3、E_nAnd others), transmitting the signals after passing through a power amplifier and a standard sound source, wherein the transmission period is T2, the transmission period T2 is far shorter than T1, equidistant target bright spots appear in a sonar image beam direction of 0 degree, a target which is larger than a preset sonar action distance index and is closest to the preset sonar action distance index is taken as a reference object AA, and a difference frequency signal S output by the standard signal source is adjusted from large to small_{Difference (D)}(t) recording the effective voltage value V2 of the difference frequency signal output by the standard signal source when the target bright spot AA disappears on the sonar image_rmsThe sound source level of the difference frequency signal emitted by the current standard sound source is the minimum detectable sound source level SL₁；

Step S6: stopping transmitting the standard sound source, analyzing the background noise of the receiving array, and recording the noise spectrum level NL in the background noise band;

step S7: SL according to minimum detectable Source level₁Calculating a minimum detectable signal-to-noise ratio by using the background noise in-band noise spectrum level NL and the propagation loss;

the difference frequency signal equivalent sound source level measurement experimental equipment comprises a transmitter and a transmitting array for transmitting an original frequency signal, a standard hydrophone for receiving the difference frequency signal, a standard filter and a standard oscilloscope;

the minimum detectable signal-to-noise ratio test experimental apparatus comprises: calculating propagation loss by using a transmitter for transmitting an original frequency signal, a transmitting array, a standard hydrophone for receiving a difference frequency signal, a standard filter and a standard oscilloscope; the method comprises the steps of utilizing a programmable signal source for transmitting a difference frequency signal, a standard power amplifier and a standard sound source, a receiving array for receiving the difference frequency signal, a receiving electronic cabin, a signal processor for detecting a target of the difference frequency signal and a display and control console for displaying the target to calculate the minimum detectable signal-to-noise ratio.

Specifically, the difference frequency signal equivalent sound source level measurement experimental equipment adopts: as shown in fig. 2, a standard hydrophone is arranged right below the auxiliary ship and at a distance H from the underwater depth, the horizontal distance between the standard hydrophone and the transmitting array is D1, and the transmitting array is at the underwater depth H; the distance D1 is greater than the original frequency far-field distance, the original frequency far-field distance is greater than the difference frequency far-field distance, and the distance D1 is not less than the equivalent end-fire array length of the nonlinear sonar nonlinear effect; the depth H is larger than the cavitation depth of the emission signal of the emission array, and the emission array rain standard hydrophones are aligned with the depth and the center of a 0-degree wave beam.

Specifically, the measured difference frequency equivalent source stage SL_{Difference (D)}The method comprises the following steps:

SL_{difference (D)}＝20lg(V1_rms)+20lg(D₁)-M (1)

Wherein M represents the standard hydrophone sensitivity; v1_rmsThe effective value of the signal voltage of the difference frequency sound signal after being received by the standard hydrophone and the filter is shown, and D1 shows the horizontal spacing of the emission matrix rain standard hydrophone.

Specifically, the minimum detectable signal-to-noise ratio test experimental equipment adopts: as shown in fig. 3, the horizontal distance between the standard hydrophone and the transmitting matrix in the difference frequency signal equivalent sound source level measurement experimental equipment is adjusted to be a distance D2, and a standard sound source is arranged right below the standard hydrophone; a receiving array is arranged right below the transmitting array; the distance D2 is greater than the difference frequency far-field distance and greater than the equivalent end-fire array length of the nonlinear sonar nonlinear effect; the depth H is larger than the cavitation depth of the transmitting signal of the transmitting array, the transmitting array is aligned with the same depth of the standard hydrophone and the center of the 0-degree wave beam, and the receiving array is aligned with the same depth of the standard sound source and the center of the 0-degree wave beam.

Specifically, the propagation loss TL employs:

TL＝SL_{difference (D)}-20lg(V_rms)+M (2)。

Specifically, the step S5 employs:

SL₁＝SL_{difference (D)}+20lg(V2_rms/V1_rms) (3)。

Specifically, the minimum detectable signal-to-noise ratio employs:

SE＝SL₁-NL-TL (4)。

the invention provides a non-linear sonar minimum detectable signal-to-noise ratio testing system, which comprises:

module M1: based on difference frequency signal equivalent sound source level measurement experimental equipment, when the nonlinear sonar normally works, difference frequency equivalent sound source level SL is actually measured_{Difference (D)}；

Module M2: when the nonlinear sonar normally works, 0-degree wave beam difference frequency signal time domain waveform S is collected and recorded_{Difference (D)}(t)；

Module M3: based on the minimum detectable signal-to-noise ratio test experimental equipment, the transmitting array transmits original frequency signals with the transmitting period of T1, the standard hydrophone receives difference frequency signals, and the voltage effective value V of the filtered difference frequency signals is recorded_rms；

Module M4: according to the effective voltage value V of the filtered difference frequency signal_rmsActually measured difference frequency equivalent sound level SL_{Difference (D)}And standard hydrophone sensitivity M, calculating propagation loss TL;

module M5: the transmitting array stops transmitting, and the standard signal source outputs the time domain waveform S of the difference frequency signal_{Difference (D)}(t) (where standard signals are not applicable, avoid E_n1、E_n2、E_n3、E_nAnd others), transmitting the signals after passing through a power amplifier and a standard sound source, wherein the transmission period is T2, the transmission period T2 is far shorter than T1, equidistant target bright spots appear in a sonar image beam direction of 0 degree, a target which is larger than a preset sonar action distance index and is closest to the preset sonar action distance index is taken as a reference object AA, and a difference frequency signal S output by the standard signal source is adjusted from large to small_{Difference (D)}(t) recording the effective voltage value V2 of the difference frequency signal output by the standard signal source when the target bright spot AA disappears on the sonar image_rmsThe sound source level of the difference frequency signal emitted by the current standard sound source is the minimum detectable sound source level SL₁；

Module M6: stopping transmitting the standard sound source, analyzing the background noise of the receiving array, and recording the noise spectrum level NL in the background noise band;

module M7: SL according to minimum detectable Source level₁Calculating a minimum detectable signal-to-noise ratio by using the background noise in-band noise spectrum level NL and the propagation loss;

the difference frequency signal equivalent sound source level measurement experimental equipment comprises a transmitter and a transmitting array for transmitting an original frequency signal, a standard hydrophone for receiving the difference frequency signal, a standard filter and a standard oscilloscope;

the minimum detectable signal-to-noise ratio test experimental apparatus comprises: calculating propagation loss by using a transmitter for transmitting an original frequency signal, a transmitting array, a standard hydrophone for receiving a difference frequency signal, a standard filter and a standard oscilloscope; the method comprises the steps of utilizing a programmable signal source for transmitting a difference frequency signal, a standard power amplifier and a standard sound source, a receiving array for receiving the difference frequency signal, a receiving electronic cabin, a signal processor for detecting a target of the difference frequency signal and a display and control console for displaying the target to calculate the minimum detectable signal-to-noise ratio.

Specifically, the difference frequency signal equivalent sound source level measurement experimental equipment adopts: as shown in fig. 2, a standard hydrophone is arranged right below the auxiliary ship and at a distance H from the underwater depth, the horizontal distance between the standard hydrophone and the transmitting array is D1, and the transmitting array is at the underwater depth H; the distance D1 is greater than the original frequency far-field distance, the original frequency far-field distance is greater than the difference frequency far-field distance, and the distance D1 is not less than the equivalent end-fire array length of the nonlinear sonar nonlinear effect; the depth H is larger than the cavitation depth of the emission signal of the emission array, and the emission array rain standard hydrophones are aligned with the depth and the center of a 0-degree wave beam.

Specifically, the measured difference frequency equivalent source stage SL_{Difference (D)}The method comprises the following steps:

SL_{difference (D)}＝20lg(V1_rms)+20lg(D₁)-M (1)

Wherein M represents the standard hydrophone sensitivity; v1_rmsThe effective value of the signal voltage of the difference frequency sound signal after being received by the standard hydrophone and the filter is shown, and D1 shows the horizontal spacing of the emission matrix rain standard hydrophone.

Specifically, the minimum detectable signal-to-noise ratio test experimental equipment adopts: as shown in fig. 3, the horizontal distance between the standard hydrophone and the transmitting matrix in the difference frequency signal equivalent sound source level measurement experimental equipment is adjusted to be a distance D2, and a standard sound source is arranged right below the standard hydrophone; a receiving array is arranged right below the transmitting array; the distance D2 is greater than the difference frequency far-field distance and greater than the equivalent end-fire array length of the nonlinear sonar nonlinear effect; the depth H is larger than the cavitation depth of the transmitting signal of the transmitting array, the transmitting array is aligned with the same depth of the standard hydrophone and the center of the 0-degree wave beam, and the receiving array is aligned with the same depth of the standard sound source and the center of the 0-degree wave beam.

Specifically, the propagation loss TL employs:

TL＝SL_{difference (D)}-20lg(V_rms)+M (2)。

Specifically, the module M5 employs:

SL₁＝SL_{difference (D)}+20lg(V2_rms/V1_rms) (3)。

Specifically, the minimum detectable signal-to-noise ratio employs:

SE＝SL₁-NL-TL (4)。

example 2

Example 2 is a preferred example of example 1

The test is carried out according to a non-linear sonar minimum detectable signal-to-noise ratio test method, in the embodiment, the original frequency far-field distance of the non-linear sonar is about 47m, the difference frequency far-field distance is about 12m, the length of the equivalent end-fire array is about 100m, and the cavitation depth is about 8 m.

Step 1, measuring equivalent sound source level of difference frequency signals, arranging test equipment as shown in figure 2, and obtaining a distance D₁100m, 10m depth H, the transmitting array is at the same depth with the standard hydrophone and the 0 degree wave beam center is aligned, when the nonlinear sonar normally works, the difference frequency signal equivalent sound source level SL is actually measured_{Difference (D)}，SL_{Difference (D)}＝203.66dB；

Step 2, recording difference frequency signal waveforms, namely collecting and recording the difference frequency signal waveform S (t) of a 0-degree wave beam when the nonlinear sonar normally works;

step 3, minimum detectable signal-to-noise ratio measurement, equipment deployment as shown in fig. 3, and distance D₂25m, depth H10 m;

step 4, transmitting the primary frequency signal by the transmitting array with a transmitting period T₁The standard hydrophone receives the difference frequency signal for 1s, and records the effective voltage value Vrms of the filtered difference frequency signal, wherein the Vrms is 9 e-6V;

step 5, calculating the propagation loss TL to be 30.37dB, wherein the standard hydrophone sensitivity M is-214.2 dB;

step 6, the transmitting array stops transmitting, and the standard sound source transmits the difference frequency signal S_{Difference (D)}(T), emission period T₂Observing sonar interface for 0.1S, adjusting S from large to small by taking a target which is larger than the action distance index and is closest to the action distance index as a reference object_{Difference (D)}(t) sound source level, when the target disappears, recording S at that time_{Difference (D)}(t) Source level of minimum detectable Source level SL₁，SL₁＝88.98(dB)；

Step 7, stopping transmitting the standard sound source, analyzing the background noise of the receiving array, and recording the in-band noise spectrum level NL of the background noise as 88.25 (dB);

and 8, calculating the minimum detectable signal-to-noise ratio SE-29.64 dB.

In this embodiment, the minimum detectable signal-to-noise ratio index requirement is-26 dB, and the measured value meets the index requirement.

In the description of the present application, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience in describing the present application and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present application.

Those skilled in the art will appreciate that, in addition to implementing the systems, apparatus, and various modules thereof provided by the present invention in purely computer readable program code, the same procedures can be implemented entirely by logically programming method steps such that the systems, apparatus, and various modules thereof are provided in the form of logic gates, switches, application specific integrated circuits, programmable logic controllers, embedded microcontrollers and the like. Therefore, the system, the device and the modules thereof provided by the present invention can be considered as a hardware component, and the modules included in the system, the device and the modules thereof for implementing various programs can also be considered as structures in the hardware component; modules for performing various functions may also be considered to be both software programs for performing the methods and structures within hardware components.

The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.