Inquiry signal detection system and detection method thereof applied to underwater positioning system

Abstract

The present invention discloses an inquiry signal detection system and a detection method thereof applied to an underwater positioning system, and relates to the field of underwater communication technology, wherein the detection method comprises the following steps: S1, an inquiry device transmits a positioning inquiry signal, wherein the positioning inquiry signal comprises a wake-up signal, an identification signal and a positioning ID signal; S2, a detection device continuously detects the signal by means of spectrum analysis, and if the detected signal contains the wake-up signal, the identification signal and the positioning ID signal, and the frequency of the positioning ID signal is consistent with the ID signal frequency preset by the detection device, then it is determined that the detected signal is the positioning inquiry signal. In this way, the inquiry signal detection method can provide a better detection effect.

Description

Technical Field

[0001] The present invention relates to the field of underwater communication technology, and in particular to an inquiry signal detection system and a detection method thereof applied to an underwater positioning system. Background Art

[0002] In recent years, countries have increasingly developed and utilized marine resources. In the process of developing and utilizing marine resources, frogmen or manned submersibles are often needed to explore and operate underwater environments. Unlike the surface environment, in the underwater environment, due to the serious attenuation of electromagnetic waves, it is necessary to use hydroacoustic communication technology to achieve communication between underwater equipment and between underwater equipment and surface equipment. One of the main purposes of communication between these devices is to locate underwater equipment to reduce danger and / or rescue underwater equipment in danger. The process of locating underwater equipment is generally that the array transmits a positioning inquiry signal, the communication machine responds after receiving the positioning inquiry signal, and the array receives the response signal. Subsequently, the location of the communication machine is located according to the content and time of the positioning inquiry signal transmitted by the array and the content and time of the response signal of the communication machine. In actual application environments, the types of signals transmitted by the array are diverse, and there may be multiple communicators in the same water area. Therefore, when a communicator receives a signal transmitted by the array, the traditional method is to use a matched filtering detection method to detect whether the signal is a positioning inquiry signal for the local machine. Since the signal is easily affected by echoes, reflections and other factors in the water, the detection effect of the matched filtering detection method is poor. Therefore, how to determine whether the signal is a positioning inquiry signal for the local machine and ensure the detection effect is a technical problem that the inventor of the present invention is committed to solving. Summary of the invention

[0003] The object of the present invention is to provide an inquiry signal detection system and a detection method thereof applied to an underwater positioning system, so as to solve the technical problems raised in the above-mentioned background technology.

[0004] To achieve the above object, the present invention provides the following technical solution: a query signal detection method applied to an underwater positioning system, comprising the following steps:

[0005] S1, the inquiry device transmits a positioning inquiry signal, wherein the positioning inquiry signal includes a wake-up signal, an identification signal and a positioning ID signal;

[0006] S2, the detection device continuously detects signals by spectrum analysis. If the detected signal contains the wake-up signal, the identification signal and the positioning ID signal, and the frequency of the positioning ID signal is consistent with the ID signal frequency preset by the detection device, the detected signal is determined to be the positioning inquiry signal.

[0007] As a further improvement of the technical solution of the present invention, the step S1 further includes the steps of:

[0008] S1.1, the query device transmits a first pulse signal, wherein the first pulse signal serves as the wake-up signal;

[0009] S1.2, after the first interval time, the query device transmits a second pulse signal, wherein the second pulse signal serves as the identification signal;

[0010] S1.3, after the second interval time, the inquiry device transmits a third pulse signal, wherein the third pulse signal serves as the positioning ID signal, wherein the frequency of the first pulse signal, the frequency of the second pulse signal and the frequency of the third pulse signal are different.

[0011] As a further improvement of the technical solution of the present invention, the duration of the first pulse signal, the duration of the second pulse signal and the duration of the third pulse signal are the same.

[0012] As a further improvement of the technical solution of the present invention, the step S2 further includes the steps of:

[0013] S2.1, moving the received original signal spectrum to the baseband signal;

[0014] S2.2, low-pass filtering the moved signal;

[0015] S2.3, downsampling the filtered signal;

[0016] S2.4, performing spectrum analysis on the downsampled signal to detect whether the signal is the positioning inquiry signal.

[0017] As a further improvement of the technical solution of the present invention, in step S2.3, the filtered signal is downsampled by 10 times.

[0018] As a further improvement of the technical solution of the present invention, the step 2.4 further comprises the steps of:

[0019] S2.4.1, take the average of m FFT calculation results near the frequency point;

[0020] S2.4.2, taking i times the mean as the threshold, if the n FFT calculation results near the frequency point have a value exceeding the threshold, it is determined that there is a peak of the frequency, thereby determining whether the pulse frequencies corresponding to the wake-up signal, the identification signal and the positioning ID signal have peaks, wherein the parameters m, n and i are all natural numbers, and m>n;

[0021] S2.4,3, when a peak value appears, exclude the m FFT calculation results near the frequency point and find the maximum value of the remaining FFT calculation results;

[0022] S2.4.4, using p times the maximum value of the remaining FFT calculation results as the fourth threshold, where the parameter p is a natural number;

[0023] S2.4.5, when the frequency peak value of the wake-up signal, the frequency peak value of the identification signal and the frequency peak value of the positioning ID signal are all greater than a fourth threshold, it is determined that the detection device has detected the positioning inquiry signal.

[0024] According to another aspect of the present invention, the present invention further provides an inquiry signal detection system for an underwater positioning system, comprising:

[0025] An inquiry device, used to transmit a positioning inquiry signal, wherein the positioning inquiry signal includes a wake-up signal, an identification signal and a positioning ID signal;

[0026] The detection device is used to continuously detect signals by spectrum analysis. If the detected signal contains the wake-up signal, the identification signal and the positioning ID signal, and the frequency of the positioning ID signal is consistent with the ID signal frequency preset by the detection device, then the detected signal is judged to be the positioning inquiry signal.

[0027] As a further improvement of the technical solution of the present invention, the inquiry device transmits the positioning inquiry signal in the following manner: first, a first pulse signal is transmitted as the wake-up signal; secondly, after a first interval, a second pulse signal is transmitted as the identification signal; and thirdly, after a second interval, a third pulse signal is transmitted as the positioning ID signal, wherein the frequency of the first pulse signal, the frequency of the second pulse signal and the frequency of the third pulse signal are different.

[0028] As a further improvement of the technical solution of the present invention, the detection device further comprises:

[0029] A shifting unit, used for shifting the received original signal spectrum to a baseband signal;

[0030] A filtering unit, used for low-pass filtering the moved signal;

[0031] A downsampling unit, used for downsampling the filtered signal;

[0032] The spectrum analysis unit is used to perform spectrum analysis on the downsampled signal to detect whether the signal is the positioning inquiry signal.

[0033] As a further improvement of the technical solution of the present invention, the downsampling unit is used to downsample the filtered signal by a factor of 10.

[0034] Compared with the prior art, the query signal detection method of the present invention has at least the following beneficial effects:

[0035] 1. The inquiry signal detection method of the present invention allows the detection device to continuously detect signals by frequency analysis. When the detected signal contains the wake-up signal, the identification signal and the positioning ID signal and the frequency of the positioning ID signal is consistent with the frequency of the preset ID signal, it is determined that the positioning inquiry signal is detected. Signals are easily affected by various factors such as echoes and reflections underwater, and the traditional matched filter detection method has poor detection effect. The present invention allows the detection device to detect signals by continuous spectrum analysis, which has a better detection effect to ensure that the detection device can detect the positioning inquiry signal.

[0036] 2. The inquiry signal detection method of the present invention allows the inquiry device to transmit a signal including three pulse signals at intervals. Among the three pulse signals, the first pulse signal is used as the wake-up signal, the second pulse signal is used as the identification signal, and the third pulse signal is used as the positioning ID signal. The frequencies of the three pulse signals are different, so that the detection device can distinguish the purpose of the signal. The wake-up signal is used to wake up multiple detection devices in an area. When these detection devices receive the signal transmitted by the inquiry device, they can judge whether the signal is the positioning inquiry signal according to the identification signal. If the signal is the positioning inquiry signal, these detection devices judge whether the positioning ID signal corresponds to the local device. Subsequently, the detection device that judges the positioning ID signal as corresponding to the local device transmits the corresponding response signal to locate the detection device (i.e., the local device) in the future. Preferably, the duration of the first pulse signal, the duration of the second pulse signal and the duration of the third pulse signal are the same. In this way, the energy of the three pulse signals on the spectrum is close, which is convenient for subsequent detection.

[0037] Other beneficial effects of the interrogation signal detection method of the present invention will be further disclosed and explained in the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of an application scenario of an inquiry signal detection system according to a preferred embodiment of the present invention.

[0039] Figure 2 It is a schematic diagram of three pulse frequencies emitted by an interrogation device of the interrogation signal detection system according to the above preferred embodiment of the present invention.

[0040] Figure 3 It is a schematic diagram of the frequency spectrum of three pulse frequencies emitted by the inquiry device of the inquiry signal detection system according to the above preferred embodiment of the present invention.

[0041] Figure 4 It is a block diagram of a detection device of the inquiry signal detection system according to the above preferred embodiment of the present invention.

[0042] Figure 5 It is a flow chart of an inquiry signal detection method according to a preferred embodiment of the present invention.

[0043] In the figure:

[0044] 100. Inquiry equipment;

[0045] 200, detection device; 201, first detection device; 202, second detection device; 203, third detection device; 204, fourth detection device; 210, moving unit; 220, filtering unit; 230, downsampling unit; 240, spectrum analysis unit. DETAILED DESCRIPTION

[0046] Before describing in detail any embodiment of the present invention, it should be understood that the present invention is not limited in its application to the construction and arrangement details of the components described below or illustrated in the following figures. The present invention can have other embodiments and can be practiced or carried out in various ways. In addition, it should be understood that the words and terms used here are for descriptive purposes and should not be considered restrictive. The use of "including" or "having" and its variations herein is intended to cover the items and their equivalents and additional items displayed below. Unless otherwise specified or limited, the terms "install", "connect", "support" and "couple" and their variations are widely used and cover direct installation and indirect installation, connection, support and connection. In addition, "connect" and "couple" are not limited to physical or mechanical connections or connections.

[0047] Furthermore, on the first aspect, in the disclosure of the present invention, the orientations or positional relationships indicated by terms such as “longitudinal”, “transverse”, “upper”, “lower”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside” and “outside” are based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore the above terms cannot be understood as limitations on the present invention; on the second aspect, the term “one” should be understood as “at least one” or “one or more”, that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the element may be multiple, and the term “one” cannot be understood as a limitation on the quantity.

[0048] The inquiry signal detection system applied to the underwater positioning system of the present invention involves the communication between the inquiry device 100 and the detection device 200. The inquiry device 100 can be a base array, and the detection device 200 can be a communication device. The inquiry device 100 and the detection device 200 are both equipped with transducers, and the communication between the inquiry device 100 and the detection device 200 is based on the underwater acoustic communication technology. Specifically, the inquiry device 100 first converts the information into an electrical signal, and then digitizes the information through an encoder, and then the transducer converts the electrical signal into an acoustic signal, which can be transmitted in water. The transducer of the detection device 200 converts the received acoustic signal into an electrical signal, and the decoder deciphers the digital information, thereby realizing the communication between the inquiry device 100 and the detection device 200. It can be understood that, based on the same method, the inquiry device 100 can also receive the information transmitted by the detection device 200.

[0049] Typically, the inquiry device 100 can be equipped on a surface device, such as a mother ship, and the detection device 200 can be installed on an underwater device, such as a frogman or a submersible, so that the underwater positioning system allows the mother ship to locate the frogman or the submersible. Nevertheless, in other specific application scenarios, the inquiry device 100 can also be equipped on an underwater device.

[0050] In some specific scenarios, the inquiry device 100 will transmit different types of signals. When the detection device 200 receives the signal transmitted by the inquiry device 100, it needs to determine whether the signal is a positioning inquiry signal. If the signal is the positioning inquiry signal, the detection device 200 can transmit a response signal for subsequent positioning of the detection device 200. In other specific scenarios, there are multiple detection devices 200 in the same area. When the detection device 200 receives the positioning inquiry signal transmitted by the inquiry device 100, it needs to determine whether the positioning inquiry signal corresponds to the local device. If the detection device 200 detects that the positioning inquiry signal transmitted by the inquiry device 100 corresponds to the local device, the detection device 200 transmits the response signal for subsequent positioning of the detection device 200. At the same time, the detection device 200 can perform friend-or-foe identification when determining whether the positioning inquiry signal corresponds to the local device, so as to prevent the detection device 200 from being illegally positioned, thereby facilitating the safety of the detection device 200.

[0051] Figures 1 to 4 The interrogation signal detection system of the present invention is shown, wherein the interrogation signal detection system comprises the interrogation device 100 and the detection device 200, and the interrogation device 100 and the detection device 200 are capable of underwater acoustic communication. In order to more clearly disclose the content and features of the interrogation signal detection system of the present invention, Figure 1 In the specific example of the interrogation signal detection system shown, the number of the detection devices 200 may be four, which are respectively a first detection device 201, a second detection device 202, a third detection device 203 and a fourth detection device 204, and the first detection device 201, the second detection device 202, the third detection device 203 and the fourth detection device 204 can respectively perform underwater acoustic communication with the interrogation device 100. It can be understood that in other specific examples of the interrogation signal detection system of the present invention, the number of the detection devices 200 may be more or less.

[0052] When it is necessary to locate the detection device 200, the inquiry device 100 is used to transmit the positioning inquiry signal, which includes a wake-up signal, an identification signal and a positioning ID signal. The detection device 200 is used to continuously detect the signal by spectrum analysis. If the detected signal contains the wake-up signal, the identification signal and the positioning ID signal and the frequency of the positioning ID signal is consistent with the frequency of the ID signal preset in the detection device 200, the detected signal is judged to be the positioning inquiry signal. Then, the detection device 200 is used to transmit the corresponding response signal for subsequent positioning of the detection device 200. Different from the matched filtering detection method used in the prior art, the detection device 200 of the inquiry signal detection system of the present invention detects whether the signal is the positioning inquiry signal by spectrum analysis, which can effectively avoid the influence of echoes, reflections and other factors on the signal underwater, and provide better detection effect.

[0053] Specifically, the inquiry device 100 transmits a signal to an area in a broadcasting form, and the first detection device 201, the second detection device 202, the third detection device 203 and the fourth detection device 204 are awakened after receiving the signal, and determine whether the signal is the positioning inquiry signal. If the result of the determination is that the signal is the positioning inquiry signal corresponding to the local device, the corresponding response signal can be transmitted. For example, when the first detection device 201 determines that the positioning inquiry signal corresponds to the local device, the first detection device 201 transmits the corresponding response signal to locate the first detection device 201, and the second detection device 202, the third detection device 203 and the fourth detection device 204 do not transmit the response signal. When the second detection device 202 determines that the positioning inquiry signal corresponds to the local device, the second detection device 202 transmits the corresponding response signal to locate the second detection device 202, and the first detection device 201, the third detection device 203 and the fourth detection device 204 do not transmit the response signal.

[0054] In a specific example of the inquiry signal detection system of the present invention, the positioning inquiry signal emitted by the inquiry device 100 is composed of three pulse signals of different frequencies, the first pulse signal is used as the wake-up signal, which is used to wake up the first detection device 201, the second detection device 202, the third detection device 203 and the fourth detection device 204, the second pulse signal is used as the identification signal, which is used to identify that the signal emitted by the inquiry device 100 is the positioning inquiry signal, and the third pulse signal is used as the positioning ID signal, which is used by the first detection device 201, the second detection device 202, the third detection device 203 and the fourth detection device 204 to determine whether the positioning inquiry signal corresponds to the local device. Since the frequencies of the pulse signals of each segment are different, and the detection device 200 presets the functions corresponding to the signals of different frequencies, the detection device 200 can easily distinguish the purpose of each pulse signal after receiving the pulse signal.

[0055] That is to say, the way in which the inquiry device 100 transmits the positioning inquiry signal is: first, the inquiry device 100 transmits a first pulse signal, and the first detection device 201, the second detection device 202, the third detection device 203 and the fourth detection device 204 can be awakened after detecting the first pulse signal; secondly, after a first interval time, the inquiry device 100 transmits a second pulse signal, and the first detection device 201, the second detection device 202, the third detection device 203 and the fourth detection device 204 can confirm after detecting the second pulse signal. The signal transmitted by the inquiry device 100 is the positioning inquiry signal. Then, after the second interval time, the inquiry device 100 transmits a third pulse signal. After detecting the third pulse signal, the first detection device 201, the second detection device 202, the third detection device 203 and the fourth detection device 204 determine whether the positioning inquiry signal transmitted by the inquiry device 100 corresponds to the local machine. The determination method is to compare whether the frequency of the third pulse signal is consistent with the frequency of the ID signal preset by the local machine. If they are consistent, the positioning inquiry signal transmitted by the inquiry device 100 is determined to correspond to the local machine. For example, after detecting the third pulse signal, the first detection device 201 determines whether the frequency of the third pulse signal transmitted by the inquiry device 100 is consistent with the frequency of the ID signal preset by the local machine. If they are consistent, the first detection device 201 determines that the positioning inquiry signal transmitted by the inquiry device 100 corresponds to the local machine. At this time, the first detection device 201 transmits the response signal for the subsequent positioning of the first detection device 201. Refer to the attached Figure 2The horizontal axis represents the number of sampling points of the detection device 200, and the vertical axis represents the acquisition amplitude of the detection device 200. The left area represents the number of sampling points and the sampling amplitude of the first pulse signal of the detection device 200, the middle area represents the number of sampling points and the sampling amplitude of the second pulse signal of the detection device 200, and the right area represents the number of sampling points and the sampling amplitude of the third pulse signal of the detection device 200. Since the three pulse signals have different frequencies, the detection device 200 can easily distinguish the purposes of the three pulse signals after sampling the three pulse signals respectively.

[0056] Preferably, the duration of the first pulse signal, the duration of the second pulse signal, and the duration of the third pulse signal emitted by the inquiry device 100 are the same, so that the energy of the three pulse signals on the spectrum is close, which facilitates the detection device 200 to detect the three pulse signals. For example, in a specific example of the inquiry signal detection system of the present invention, the duration of the first pulse signal, the duration of the second pulse signal, and the duration of the third pulse signal emitted by the inquiry device 100 are all 20ms.

[0057] It is worth mentioning that, in the process of the inquiry device 100 transmitting the positioning inquiry signal, the duration of the first interval time and the second interval time may be the same or different. For example, in this specific example of the inquiry signal detection system of the present invention, the first interval time and the second interval time are both 10ms.

[0058] That is, in a specific example of the inquiry signal detection system of the present invention, the frequencies of the three-segment pulse signals emitted by the inquiry device 100 are as follows in reference to Table 1:

[0059] Table 1 Frequency of three-segment pulse signals

[0060]

[0061] The frequency of the ID signal preset by the first detection device 201 is 31kHz, the frequency of the ID signal preset by the second detection device 202 is 32kHz, the frequency of the ID signal preset by the third detection device 203 is 33kHz, and the frequency of the ID signal preset by the fourth detection device 204 is 34kHz. The inquiry device 100 transmits a first pulse signal with a frequency of 28kHz for 20ms to wake up the first detection device 201, the second detection device 202, the third detection device 203 and the fourth detection device 204. After an interval of 10ms, the inquiry device 100 transmits a second pulse signal with a frequency of 29kHz for 20ms to be used by the first detection device 201, the second detection device 202, the third detection device 203 and the fourth detection device 204 to determine that the signal transmitted by the inquiry device 100 is the positioning inquiry signal. After an interval of 10ms, if the inquiry device 100 transmits a third pulse signal with a frequency of 20ms and 31kHz, the first detection device 201 can determine that the positioning ID signal included in the positioning inquiry signal transmitted by the inquiry device 100 corresponds to the local device after detecting the third pulse signal. At this time, the first detection device 201 transmits the response signal. If the inquiry device 100 transmits a third pulse signal with a frequency of 20ms and 32kHz, the second detection device 202 can determine that the positioning ID signal included in the positioning inquiry signal transmitted by the inquiry device 100 corresponds to the local device after detecting the third pulse signal. At this time, the second detection device 202 transmits the response signal. If the inquiry device 100 transmits a third pulse signal with a frequency of 20ms and 33kHz, the third detection device 203 can determine that the positioning ID signal included in the positioning inquiry signal transmitted by the inquiry device 100 corresponds to the local machine after detecting the third pulse signal. At this time, the third detection device 203 transmits the response signal. If the inquiry device 100 transmits a third pulse signal with a frequency of 20ms and 34kHz, the fourth detection device 204 can determine that the positioning ID signal included in the positioning inquiry signal transmitted by the inquiry device 100 corresponds to the local machine after detecting the third pulse signal. At this time, the fourth detection device 204 transmits the response signal.

[0062] In the inquiry signal detection system of the present invention, the inquiry signal detection system directly realizes the detection of the positioning inquiry signal by spectrum analysis. The specific detection steps may be: first, the received original signal spectrum is shifted to the baseband signal, and the shift frequency may be 30kHz. For example, in the specific method in which the detection device 200 uses FPGA to detect the positioning inquiry signal, the built-in generation IP of FPGA can be used to generate 30kHz sine waves and cosine waves, and then the spectrum shift is realized by orthogonal transformation; secondly, the shifted signal is low-pass filtered, for example, the filter system can be first generated in matlab, and then pre-stored in the FPGA memory to be realized by multiplication and accumulation; thirdly, the filtered signal is downsampled, and the downsampling ratio can be selected as needed; finally, the downsampled signal is spectrum analyzed to detect whether the signal is the positioning inquiry signal. Since the inquiry signal detection system performs spectrum shifting in the process of detecting the positioning inquiry signal, the frequency after the shifting is actually detected as shown in Table 2:

[0063] Table 2 Frequency after relocation

[0064]

[0065] In the inquiry signal detection system of the present invention, by moving the received original signal spectrum to the baseband signal, the signal distortion caused by downsampling can be effectively avoided. By low-pass filtering the moved signal, the interference of noise can be reduced or even avoided. By downsampling the filtered signal, the number of FFT points can be greatly reduced, the amount of calculation can be reduced, and the calculation time can be saved, so as to improve the detection efficiency of the detection device 200.

[0066] In addition, Figure 4 A specific example of the detection device 200 is shown, and the detection device 200 includes a shifting unit 210, a filtering unit 220, a downsampling unit 230 and a spectrum analysis unit 240, wherein the shifting unit 210 is used to shift the received original signal spectrum to the baseband signal, and the shifting frequency can be 30kHz, so the frequency of the signal detected by the detection device 200 after being shifted is shown in Table 2, and by shifting the received original signal spectrum to the baseband signal, the distortion of the downsampled signal can be effectively avoided, wherein the filtering unit 220 is used to perform low-pass filtering on the shifted signal to reduce or even avoid clutter interference, wherein the downsampling unit 230 is used to downsample the filtered signal, greatly reducing the number of FFT points, reducing the amount of calculation and saving calculation time, so as to improve the detection efficiency of the detection device 200, wherein the spectrum analysis unit 240 is used to perform spectrum analysis on the downsampled signal to detect whether the signal is the positioning inquiry signal.

[0067] In some embodiments of the present invention, the downsampling ratio may be 10 times, that is, the filtered signal is downsampled 10 times. Since the filtered signal is downsampled 10 times, the FFT calculation of 2048 points can simultaneously include the three pulse frequencies in the positioning inquiry signal, and the detection device 200 will only detect whether there are peaks at the three required frequency points of the wake-up signal, the identification signal and the positioning ID signal in the subsequent spectrum analysis process. Therefore, spectrum analysis of the signal after being downsampled 10 times is sufficient for detecting the positioning inquiry signal.

[0068] The spectrum analysis unit 240 performs spectrum analysis on the downsampled signal to detect whether the signal is the positioning inquiry signal by detecting whether there are only three obvious frequency peaks near the required frequency point.

[0069] Specifically, the specific method for detecting whether there is a frequency peak near a frequency point is: take the average of m FFT calculation results near the frequency point, and then use i times the average as the threshold. If the n FFT calculation results near the frequency point have a value exceeding the threshold, it is judged that there is a peak of the frequency, wherein the parameters m, n and i are all natural numbers, and m>n. For example, in a specific example of the inquiry signal detection system of the present invention, the value of m is 80, the value of n is 20, and the value of i is 3, that is, take the average of 80 FFT calculation results near the frequency point, and then use 3 times the average as the threshold. If the 20 FFT calculation results near the frequency point have a value exceeding the threshold, it is judged that there is a peak of the frequency.

[0070] Since the transducer of the detection device 200 responds differently to different frequencies, the frequency peaks calculated by FFT are also different. In order to avoid the situation where a certain frequency cannot be detected, the detection device 200 of the inquiry signal detection system of the present invention needs to define respective thresholds and calculate them separately when detecting three pulse frequencies. Specifically, in order for the detection device 200 to detect whether there is a frequency peak at the frequency corresponding to the wake-up signal, first, the 80 FFT calculation results near the frequency point of the first pulse frequency are averaged, and then 3 times the average is used as the threshold of the frequency point of the first pulse frequency. Finally, if the 20 FFT calculation results near the frequency point of the first pulse frequency have a value exceeding this threshold, it is judged that the first pulse frequency has a frequency peak. In order for the detection device 200 to detect whether there is a frequency peak at the frequency corresponding to the identification signal, first, the 80 FFT calculation results near the frequency point of the second pulse frequency are averaged, and then 3 times the average is used as the threshold of the frequency point of the second pulse frequency. Finally, if the 20 FFT calculation results near the frequency point of the second pulse frequency have a value exceeding this threshold, it is judged that the second pulse frequency has a frequency peak. In order to enable the detection device 200 to detect whether there is a frequency peak in the frequency corresponding to the positioning ID signal, first, the 80 FFT calculation results near the frequency point of the third pulse frequency are averaged, and secondly, 3 times the average is used as the threshold of the frequency point of the third pulse frequency. Finally, if the 20 FFT calculation results near the frequency point of the third pulse frequency have a value exceeding this threshold, it is determined that the third pulse frequency has a frequency peak.

[0071] The normal positioning inquiry signal should contain only three obvious frequency peaks near the frequency points of the three pulse frequencies, but sometimes the noise signal may also exceed the threshold corresponding to the frequency points of the three pulse frequencies. If the detected signal is judged as the positioning inquiry signal only by detecting the presence of peaks near the frequency points of the three pulse frequencies, the noise signal may also be mistakenly judged as the positioning inquiry signal. Therefore, it is necessary to further eliminate the noise signal to ensure that the detection device 200 accurately detects the positioning inquiry signal.

[0072] Since the amplitude distribution of the entire spectrum of the noise signal is relatively messy and there are no three obvious frequency peaks, the noise signal can be excluded by using the difference in spectrum morphology to ensure that only three relatively obvious frequency peaks are included near the required frequency point, thereby accurately detecting the positioning inquiry signal. In order to ensure that there are only three obvious frequency peaks near the required frequency point, the specific method of the present invention is to exclude 80 FFT calculation results near the frequency point, find the maximum value of the remaining FFT calculation results, and use p times (for example, 5 times) of this maximum value as the fourth threshold value in addition to the above three threshold values, and then determine whether the above three frequency peaks are all greater than the fourth threshold value. Only when the above three frequency peaks are all greater than the fourth threshold value, the detection device 200 determines that the detected signal is the positioning inquiry signal. In addition, when the frequency of the positioning ID signal of the positioning inquiry signal is consistent with the frequency of the positioning ID signal preset by the detection device 200, it is determined that the positioning inquiry signal is sent to the local machine. At this time, the detection device 200 transmits the response signal. Refer to the attached Figure 3 , the horizontal axis is the number of FFT points, and the vertical axis is the FFT calculation amplitude, where threshold 1 is the threshold of the frequency point of the first pulse frequency, threshold 2 is the threshold of the frequency point of the second pulse frequency, threshold 3 is the threshold of the frequency point of the third pulse frequency, and threshold 4 is the fourth threshold in addition to threshold 1, threshold 2 and threshold 3.

[0073] In other words, the step of performing spectrum analysis on the downsampled signal further includes: first, taking the average of m FFT calculation results near the frequency point; second, taking i times the average as the threshold, if the n FFT calculation results near the frequency point have a value exceeding the threshold, it is judged that there is a peak of the frequency, so as to judge whether the pulse frequencies corresponding to the wake-up signal, the identification signal and the positioning ID signal have peaks, wherein the parameters m, n and i are all natural numbers, and m>n; third, when a peak appears, the m FFT calculation results near the frequency point are excluded, and the maximum value of the remaining FFT calculation results is found; fourth, taking p times the maximum value of the remaining FFT calculation results as the fourth threshold, wherein the parameter p is a natural number; fifth, when the frequency peak of the wake-up signal, the frequency peak of the identification signal and the frequency peak of the positioning ID signal are all greater than the fourth threshold, it is judged that the detection device has detected the positioning inquiry signal.

[0074] Reference Figure 5According to another aspect of the present invention, the present invention further provides an inquiry signal detection method applied to an underwater positioning system, wherein the inquiry signal detection method comprises the following steps: S1, the inquiry device 100 transmits the positioning inquiry signal, wherein the positioning inquiry signal comprises the wake-up signal, the identification signal and the positioning ID signal; S2, the detection device 200 continuously detects the signal by spectrum analysis, and if the detected signal contains the wake-up signal, the identification signal and the positioning ID signal, and the frequency of the positioning ID signal is consistent with the ID signal frequency preset by the detection device 200, then the detected signal is judged to be the positioning inquiry signal. Different from the matched filtering detection method adopted in the prior art, the inquiry signal detection method of the present invention allows the detection device 200 to detect whether the signal is the positioning inquiry signal by spectrum analysis, which can effectively avoid the influence of echoes, reflections and other factors on the signal underwater, and provide a better detection effect.

[0075] In an example of the inquiry signal detection method of the present invention, the step S1 further includes the following steps: S1.1, the inquiry device 100 transmits a first pulse signal, wherein the first pulse signal is used as the wake-up signal; S1.2, after a first interval, the inquiry device 100 transmits a second pulse signal, wherein the second pulse signal is used as the identification signal; S1.3, after a second interval, the inquiry device 100 transmits a third pulse signal, wherein the third pulse signal is used as the positioning ID signal. It should be noted that the frequency of the first pulse signal, the frequency of the second pulse signal and the frequency of the third pulse signal are different, so that the detection device 200 can distinguish the purpose of the three pulse signals. For example, in a specific example of the inquiry signal detection method of the present invention, the frequency of the first pulse signal can be 28kHz, the frequency of the second pulse signal can be 29kHz, and the frequency of the third pulse signal can be 31kHz, 32kHz, 33kHz and 34kHz.

[0076] Preferably, the duration of the first pulse signal, the duration of the second pulse signal and the duration of the third pulse signal are the same, for example, the duration of the three pulse signals are all 20 ms.

[0077] In an example of the inquiry signal detection method of the present invention, the step S2 further includes the following steps: S2.1, moving the received original signal spectrum to the baseband signal; S2.2, low-pass filtering the moved signal; S2.3, downsampling the filtered signal; S2.4, spectrum analysis of the downsampled signal to detect whether the signal is the positioning inquiry signal. In the inquiry signal detection method of the present invention, by moving the received original signal spectrum to the baseband signal, the signal distortion caused by downsampling can be effectively avoided, by low-pass filtering the moved signal, the interference of clutter can be reduced or even avoided, and by downsampling the filtered signal, the number of FFT points can be greatly reduced, the amount of calculation can be reduced, and the calculation time can be saved, so as to improve the detection efficiency of the detection device 200.

[0078] In an example of the inquiry signal detection method of the present invention, the step 2.4 further includes the steps: S2.4.1, taking the average of m FFT calculation results near the frequency point; S2.4.2, taking i times the average as the threshold, if the n FFT calculation results near the frequency point have a value exceeding the threshold, it is judged that there is a peak of the frequency, so as to judge whether the pulse frequencies corresponding to the wake-up signal, the identification signal and the positioning ID signal have peaks, wherein the parameters m, n and i are all natural numbers, and m>n; S2.4,3, when a peak appears, exclude the m FFT calculation results near the frequency point, and find the maximum value of the remaining FFT calculation results; S2.4.4, taking p times the maximum value of the remaining FFT calculation results as the fourth threshold, wherein the parameter p is a natural number; S2.4.5, when the frequency peak of the wake-up signal, the frequency peak of the identification signal and the frequency peak of the positioning ID signal are all greater than the fourth threshold, it is judged that the detection device has detected the positioning inquiry signal.

[0079] For example, in a specific example of the inquiry signal detection system of the present invention, in the step S2.3, the filtered signal is downsampled by 10 times. When the value of m is 80, the value of n is 20, the value of i is 3, and the value of p is 5, in the step S2.4.1, 80 FFT calculation results near the frequency point are averaged. In the step S2.4.2, 3 times the average is used as the threshold. If the 20 FFT calculation results near the frequency point have a value exceeding the threshold, it is determined that there is a peak of the frequency, thereby determining the wake-up signal, the Whether the pulse frequency corresponding to the identification signal and the positioning ID signal has a peak. In S2.4,3, when a peak appears, the 80 FFT calculation results near the frequency point are excluded, and the maximum value of the remaining FFT calculation results is found. In S2.4.4, 5 times the maximum value of the remaining FFT calculation results is used as the fourth threshold. In S2.4.5, when the frequency peak value of the wake-up signal, the frequency peak value of the identification signal and the frequency peak value of the positioning ID signal are all greater than the fourth threshold, it is determined that the detection device has detected the positioning inquiry signal.

[0080] It should be understood by those skilled in the art that the embodiments of the present invention described above and shown in the accompanying drawings are only examples and do not limit the present invention. The purpose of the present invention has been fully and effectively achieved. The functional and structural principles of the present invention have been demonstrated and explained in the embodiments, and the embodiments of the present invention may be modified or altered in any way without departing from the principles.

Claims

1. A method for detecting an inquiry signal applied to an underwater positioning system, characterized in that: The inquiry signal detection method comprises the following steps: S1, the inquiry device transmits a positioning inquiry signal, wherein the positioning inquiry signal includes a wake-up signal, an identification signal and a positioning ID signal; S2, the detection device continuously detects signals by spectrum analysis. If the detected signal contains the wake-up signal, the identification signal and the positioning ID signal, and the frequency of the positioning ID signal is consistent with the ID signal frequency preset by the detection device, then the detected signal is determined to be the positioning inquiry signal; Wherein said step S2 further comprises the steps of: S2.1, when the detection device uses FPGA to detect the positioning inquiry signal, a sine wave and a cosine wave are generated using the built-in generation IP of the FPGA, and the received original signal spectrum is moved to a baseband signal by orthogonal transformation; S2.2, first generate the filter system in matlab, then pre-store it in the FPGA memory to implement low-pass filtering of the moved signal through multiplication and accumulation; S2.3, downsampling the filtered signal; S2.4, performing spectrum analysis on the downsampled signal to detect whether the signal is the positioning inquiry signal, wherein step S2.4 further comprises the following steps: S2.4.1, take the average of m FFT calculation results near the frequency point; S2.4.2, taking i times the mean as the threshold, if the n FFT calculation results near the frequency point have a value exceeding the threshold, it is determined that there is a component of the frequency, thereby determining whether the pulse frequency corresponding to the wake-up signal, the identification signal and the positioning ID signal has a peak, wherein the parameters m, n and i are all natural numbers, and m>n; S2.4.3, when a peak value appears, exclude the m FFT calculation results near the frequency point and find the maximum value of the remaining FFT settlement results; S2.4.4, taking p times the maximum value of the remaining FFT settlement results as the fourth threshold, where the parameter p is a natural number; S2.4.5, when the frequency peak value of the wake-up signal, the frequency peak value of the identification signal and the frequency peak value of the positioning ID signal are all greater than a fourth threshold, determine that the detection device has detected the positioning inquiry signal.

2. The inquiry signal detection method according to claim 1, characterized in that: The step S1 further comprises the steps of: S1.1, the query device transmits a first pulse signal, wherein the first pulse signal serves as the wake-up signal; S1.2, after the first interval time, the query device transmits a second pulse signal, wherein the second pulse signal serves as the identification signal; S1.3, after the second interval time, the inquiry device transmits a third pulse signal, wherein the third pulse signal serves as the positioning ID signal, wherein the frequency of the first pulse signal, the frequency of the second pulse signal and the frequency of the third pulse signal are different.

3. The inquiry signal detection method according to claim 2, characterized in that: The duration of the first pulse signal, the duration of the second pulse signal and the duration of the third pulse signal are the same.

4. The inquiry signal detection method according to claim 1, characterized in that: In step S2.3, the filtered signal is downsampled by a factor of 10.

5. The inquiry signal detection method according to claim 4, characterized in that: When the value of m is 80, the value of n is 20, the value of i is 3, and the value of p is 5, in step 2.4.1, the 80 FFT calculation results near the frequency point are averaged, and in step S2.4.2, 3 times the average is used as the threshold. If the 20 FFT calculation results near the frequency point have a value exceeding the threshold, it is determined that there is a peak of the frequency, thereby determining whether the pulse frequencies corresponding to the wake-up signal, the identification signal and the positioning ID signal have peaks. In step S2.4.3, when a peak appears, the 80 FFT calculation results near the frequency point are excluded, and the maximum value of the remaining FFT calculation results is found. In step S2.4.4, 5 times the maximum value of the remaining FFT calculation results is used as the fourth threshold. In step S2.4.5, when the frequency peak of the wake-up signal, the frequency peak of the identification signal and the frequency peak of the positioning ID signal are all greater than the fourth threshold, it is determined that the detection device has detected the positioning inquiry signal.

6. An inquiry signal detection system for an underwater positioning system, characterized in that: The inquiry signal detection system comprises: An inquiry device, used to transmit a positioning inquiry signal, wherein the positioning inquiry signal includes a wake-up signal, an identification signal and a positioning ID signal; A detection device, used for continuously detecting signals by spectrum analysis, and if the detected signal contains the wake-up signal, the identification signal and the positioning ID signal, and the frequency of the positioning ID signal is consistent with the ID signal frequency preset by the detection device, then determining that the detected signal is the positioning inquiry signal; The detection device comprises: A moving unit, used to move the received original signal spectrum to a baseband signal. When the detection device uses FPGA to detect the positioning inquiry signal, the moving unit uses the built-in generation IP of FPGA to generate sine waves and cosine waves, and moves the received original signal spectrum to the baseband signal by orthogonal transformation. A filtering unit is used to perform low-pass filtering on the moved signal. The filtering unit first generates a filter system in Matlab, and then pre-stores it in the FPGA memory to implement low-pass filtering on the moved signal through multiplication and accumulation; A downsampling unit, used for downsampling the filtered signal; A spectrum analysis unit is used to perform spectrum analysis on the downsampled signal to detect whether the signal is the positioning inquiry signal, wherein the spectrum analysis unit performs spectrum analysis on the downsampled signal to detect whether the signal is the positioning inquiry signal in the following manner: taking the average of m FFT calculation results near the frequency point; taking i times the average as a threshold, if the n FFT calculation results near the frequency point have a value exceeding the threshold, it is judged that there is a component of the frequency, thereby judging whether a peak value appears in the pulse frequencies corresponding to the wake-up signal, the identification signal and the positioning ID signal, wherein parameters m, n and i are all natural numbers, and m>n; when a peak value appears, the m FFT calculation results near the frequency point are excluded, and the maximum value of the remaining FFT settlement results is found; p times the maximum value of the remaining FFT settlement results is taken as a fourth threshold, wherein parameter p is a natural number; when the frequency peak value of the wake-up signal, the frequency peak value of the identification signal and the frequency peak value of the positioning ID signal are all greater than the fourth threshold, it is judged that the detection device has detected the positioning inquiry signal.

7. The inquiry signal detection system according to claim 6, characterized in that: The inquiry device transmits the positioning inquiry signal in the following manner: first, a first pulse signal is transmitted as the wake-up signal; second, after a first interval, a second pulse signal is transmitted as the identification signal; and third, after a second interval, a third pulse signal is transmitted as the positioning ID signal, wherein the frequency of the first pulse signal, the frequency of the second pulse signal and the frequency of the third pulse signal are different.

8. The inquiry signal detection system according to claim 6, characterized in that: The downsampling unit is used to downsample the filtered signal by a factor of 10.

9. The inquiry signal detection system according to claim 6, characterized in that: When the value of m is 80, the value of n is 20, the value of i is 3, and the value of p is 5, the average of 80 FFT calculation results near the frequency point is taken, and 3 times the average is used as the threshold. If the 20 FFT calculation results near the frequency point have a value exceeding the threshold, it is determined that there is a peak of the frequency, so as to determine whether the pulse frequencies corresponding to the wake-up signal, the identification signal and the positioning ID signal have peaks. When a peak appears, the 80 FFT calculation results near the frequency point are excluded, and the maximum value of the remaining FFT calculation results is found. 5 times the maximum value of the remaining FFT calculation results is used as the fourth threshold. When the frequency peak of the wake-up signal, the frequency peak of the identification signal and the frequency peak of the positioning ID signal are all greater than the fourth threshold, it is determined that the detection device has detected the positioning inquiry signal.

10. The inquiry signal detection system according to claim 7, characterized in that: The duration of the first pulse signal, the duration of the second pulse signal and the duration of the third pulse signal are the same.

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