CN114019453B - Ranging method based on underwater acoustic baseline positioning system - Google Patents
Ranging method based on underwater acoustic baseline positioning system Download PDFInfo
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Abstract
The invention relates to the field of underwater sound measurement, and provides a distance measurement method based on an underwater sound baseline positioning system, which comprises the following steps: determining a transmitting signal corresponding to an original signal based on a preset spread spectrum signal and a modulation signal, wherein the original signal comprises transmitting time information; transmitting the transmit signal into an underwater acoustic environment; determining a valid signal and a frequency correction value from the continuously received underwater sound signal; determining a correlation detection signal based on the spread spectrum signal, the modulation signal and the frequency correction value; determining time of arrival information of the valid signal based on the correlation detection signal; determining a propagation time of the transmit signal and a distance of the transmit unit to the receive unit based on the modulated signal, the spread signal, and the effective signal. The method provided by the invention can accurately realize high-precision distance measurement based on the underwater acoustic baseline positioning system.
Description
Technical Field
The application relates to the field of underwater sound measurement, in particular to a distance measurement method based on an underwater sound baseline positioning system.
Background
The acoustic positioning technology is widely applied to ocean development, and a Long Base Line (LBL), a Short Base Line (SBL) and an Ultra-Short Base Line (USBL) acoustic positioning system are underwater acoustic positioning systems which are widely applied in recent years and have a rapid development speed. Limited by the rapid attenuation characteristics of electromagnetic waves in a marine environment, underwater positioning system propagation media have turned to the use of acoustic wave substitution.
The long baseline and short baseline positioning system mainly depends on positioning by an acoustic ranging method, ranging by an acoustic communication mode, and positioning of a target point by positioning algorithms such as back intersection of a plurality of acoustic elements; the ultra-short baseline positioning system also measures distance by means of an acoustic communication method, acquires a target azimuth by means of multi-primitive joint direction finding, and solves target point positioning by means of distance measurement and direction finding. Based on the working mode of the underwater acoustic baseline positioning system, the acoustic ranging method is one of the key positioning technologies, and the ranging precision directly affects the positioning precision.
Under the traditional narrow-band pulse signaling and the working mode thereof, a plurality of defects are exposed when the narrow-band pulse signaling faces a severe marine environment, the narrow-band signal is difficult to capture when reaching an acoustic array after being transmitted through a complex underwater sound field environment, and equivalent information is lost. The existing distance measuring mode of the acoustic positioning system at home and abroad mostly adopts the second-generation digital broadband spread spectrum signal communication technology to measure the phase, and then the distance measuring data is obtained, so that the problems of multipath interference, Doppler spread and the like are solved.
The existing phase and distance measurement by utilizing a second-generation digital spread spectrum signal communication technology is limited by the characteristic of low acoustic transmission rate, the distance measurement precision between a single pair of acoustic elements and an acoustic responder in China can reach a decimeter level at the highest, and the effect is still discounted under the environment of a shallow sea complex sea area. In the existing underwater acoustic digital broadband spread spectrum communication mode, in view of the wireless CDMA technology, the phase and distance measurement process is carried out by adopting a pseudo-random code synchronization process, so that the natural system precision limit exists, and the synchronization precision, namely the distance measurement precision, is changed along with the code element width. The existing distance measurement method is only broadband communication interactive information, and is not a high-precision distance measurement method specially designed for underwater sound positioning targets. An improved method for ranging an existing underwater sound broadband spread spectrum communication technology is found, the overall positioning precision of the system is improved, the system can stably work under the complex sea area sound field environment in accordance with the working mode of the underwater sound baseline positioning system, and the main problem of the underwater sound baseline positioning system is solved.
Due to various defects of the prior art, finding a high-precision distance measurement method capable of meeting the acoustic baseline positioning system becomes a research focus for solving the problem of distance measurement and positioning of the underwater acoustic baseline positioning system.
Disclosure of Invention
The application aims to provide a distance measurement method based on an underwater acoustic baseline positioning system, which is used for solving the problems in the prior art.
The embodiment of the application can be realized by the following technical scheme:
a distance measurement method based on an underwater acoustic baseline positioning system comprises the following steps:
s100: determining a transmitting signal corresponding to an original signal based on a preset spread spectrum signal and a preset modulation signal, wherein the original signal comprises transmitting time information;
s200: transmitting the transmit signal into an underwater acoustic environment using a transmit unit of the underwater acoustic baseline positioning system;
s300: determining a valid signal and a frequency correction value from an underwater sound signal continuously received by a receiving unit of the underwater sound baseline positioning system, wherein the valid signal is a signal received by the receiving unit after the transmitting signal propagates through an underwater sound environment, and the frequency correction value is determined based on the modulation signal and the valid signal;
s400: determining a correlation detection signal based on the spread spectrum signal, the modulation signal and the frequency correction value;
s500: performing sliding correlation detection on the effective signal based on the correlation detection signal, and determining arrival time information of the effective signal;
s600: acquiring the transmission time information based on the modulation signal, the spread spectrum signal and the effective signal, and determining the propagation time of the transmission signal and the distance from the transmitting unit to the receiving unit based on the transmission time information and the arrival time information.
Further, the step S100 of determining a transmission signal corresponding to the original signal based on the spread spectrum signal and the modulation signal further includes the following steps:
spreading the original signal by using the spread spectrum signal to obtain a spread spectrum original signal; and carrying out differential phase shift keying modulation on the spread original signal by using the modulation signal to obtain the transmitting signal.
Further, the spread spectrum signal is a pseudo random code sequence.
Preferably, the spread spectrum signal is a GOLD sequence.
Further, the step S300 of determining a valid signal and a frequency correction value from the underwater sound signal continuously received by the receiving unit of the underwater sound baseline positioning system further includes the following steps:
s310: continuously receiving an underwater acoustic signal using a receiving unit of the underwater acoustic baseline positioning system;
s320: calculating the frequency spectrum of the continuously received underwater sound signal in real time;
s330: searching the frequency spectrum of the continuously received underwater sound signal in the Doppler frequency shift searching range, judging whether a frequency peak exceeding a frequency peak detection threshold exists, if so, returning to the step S310, and if true, executing the step S340, wherein,
s340: and performing signal rollback and signal interception on the underwater sound signal with the true judgment result to obtain an effective signal, and calculating the difference value between the peak frequency of the effective signal and the peak frequency of the modulation signal to obtain the frequency correction value.
Preferably, the doppler shift search range is determined based on the modulation signal, and the frequency peak detection threshold is determined based on performance of the underwater acoustic baseline positioning system.
Further, the step S400 further includes the steps of:
carrying out differential phase shift keying modulation on the spread spectrum signal by using the modulation signal to obtain a correlation detection signal; and performing frequency correction on the correlation detection signal by using the frequency correction value.
Further, the step S500 further includes the steps of:
s510: setting an initial value and a sliding step length of a relative position of the correlation detection signal and the effective signal;
s520: calculating a correlation of the correlation detection signal and the valid signal;
s530: judging whether the correlation exceeds a correlation threshold value, if the judgment result is false, executing step S540, returning to execute step S520, if the judgment result is true, executing step S550, wherein,
s540: resetting the relative position of the correlation detection signal and the effective signal according to the sliding step length;
s550: and determining the arrival time of the effective signal according to the position of the correlation detection signal relative to the effective signal when the judgment result is a true value.
Preferably, the correlation threshold is determined based on a property of the spread spectrum signal.
Further, the step S600 of obtaining the transmission time information based on the modulation signal, the spread spectrum signal and the effective signal further includes the following steps:
carrying out coherent demodulation processing on the effective signal based on the modulation signal to obtain a demodulated effective signal; sampling and judging the demodulated effective signal to obtain a judgment signal; de-spreading the decision signal based on the spread spectrum signal to obtain the original signal; acquiring the transmission time information based on the original signal.
The distance measurement method based on the underwater acoustic baseline positioning system provided by the embodiment of the application at least has the following beneficial effects:
(1) the technical scheme of the application determines the initial position of the effective signal by adopting a mode of judging a sliding correlation method of the received effective signal and a correlation detection signal generated locally, and is different from a detection method of extracting code element information by a demodulation means and then synchronizing code elements in the prior art;
(2) the technical scheme of the application firstly demodulates the effective signal and then despreads the effective signal, and is different from the step of despreading and then demodulating the effective signal in the existing communication process.
Drawings
Fig. 1 is a flowchart of a distance measurement method based on an underwater acoustic baseline positioning system according to an embodiment of the present application;
FIG. 2 is a waveform of an original signal according to an embodiment of the present application;
fig. 3 is a schematic diagram of generating a GOLD sequence according to an embodiment of the present application;
fig. 4 illustrates auto-correlation and cross-correlation properties of GOLD sequences according to an embodiment of the present application;
FIG. 5 is a waveform of an original signal after spreading according to an embodiment of the present application;
FIG. 6 is a time domain and frequency domain waveform of a transmit signal in accordance with an implementation of the present application;
FIG. 7 is a flowchart of determining valid signal and frequency correction values according to an embodiment of the present application;
FIG. 8 is a frequency domain waveform of an effective signal according to an embodiment of the present application;
fig. 9 is a flowchart of step S500 according to an embodiment of the present application;
FIG. 10 is a graph of correlation between a correlation detection signal and a valid signal as a function of relative position according to an embodiment of the present application;
FIG. 11 is a diagram illustrating coherent demodulation of a desired signal according to an embodiment of the present application;
fig. 12 is a waveform diagram of an original signal resulting from despreading a sampled decision signal according to an embodiment of the present application;
fig. 13 shows simulation results at different signal-to-noise ratios according to an embodiment of the present application.
Detailed Description
Hereinafter, the technical solutions of the present application will be clearly and completely described in conjunction with the embodiments of the present application and with reference to the accompanying drawings, and it should be noted that the embodiments described below are for enabling those skilled in the art to better understand the technical solutions of the present application, and do not represent all the embodiments of the present application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The use of "first," "second," and the like in the description, claims, and drawings of this application is for the purpose of distinguishing between similar elements or objects, and is not intended to limit the order or sequence in which a particular element or sequence is claimed, or to imply relative importance. Furthermore, the terms "comprises," "comprising," and any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, or article that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, or article.
Unless expressly stated or limited otherwise, the terms "disposed," "connected," and "connected" are to be construed broadly and encompass, for example, fixed, removable, or integral connections; they may be mechanically coupled, directly coupled, indirectly coupled through intervening media, or may be interconnected between two elements. The specific meaning of the above terms in the present application will be specifically understood by those skilled in the art.
In order to solve the problems in the prior art described in the background art, an embodiment of the present application provides a distance measurement method based on an underwater acoustic baseline positioning system, and fig. 1 is a flowchart of a distance measurement method based on an underwater acoustic baseline positioning system provided in the present application, and as shown in fig. 1, the method includes the following steps:
s100: determining a transmitting signal corresponding to an original signal based on a preset spread spectrum signal and a preset modulation signal, wherein the original signal comprises transmitting time information;
s200: transmitting the transmit signal into an underwater acoustic environment using a transmit unit of the underwater acoustic baseline positioning system;
s300: determining a valid signal and a frequency correction value from an underwater sound signal continuously received by a receiving unit of the underwater sound baseline positioning system, wherein the valid signal is a signal received by the receiving unit after the transmitting signal propagates through an underwater sound environment, and the frequency correction value is determined based on the modulation signal and the valid signal;
s400: determining a correlation detection signal based on the spread spectrum signal, the modulation signal and the frequency correction value;
s500: performing sliding correlation detection on the effective signal based on the correlation detection signal, and determining arrival time information of the effective signal;
s600: acquiring the transmission time information based on the modulation signal, the spread spectrum signal and the effective signal, and determining the propagation time of the transmission signal and the distance from the transmitting unit to the receiving unit based on the transmission time information and the arrival time information.
The underwater acoustic baseline positioning system used in the ranging method provided in the embodiment of the present application transmits and receives an original signal in an underwater acoustic environment, and the specific structure of the transmitting unit and the receiving unit included in the underwater acoustic baseline positioning system and the working principle of transmitting and receiving a signal in an underwater acoustic environment are known to those skilled in the art.
Preferred implementations of the embodiments of the present application will be described in detail below with reference to the accompanying drawings.
Step S100 of this embodiment is a step of performing spreading and carrier modulation on an original signal by using a preset spreading signal and a preset modulation signal to obtain a transmission signal, where the original signal includes transmission time information for resolving a propagation time of a final transmission signal in an underwater acoustic environment.
In some embodiments of this embodiment, the original signal is a digital signal containing unix time stamps; in other embodiments of this embodiment, other formats of transmission time information may be added to the original signal. Techniques for inserting specific information into a digital signal are known to those skilled in the art. Fig. 2 shows a waveform of an original signal according to a specific embodiment of the present embodiment.
In some embodiments of this embodiment, an original signal is first spread by using a pseudo-random code sequence to obtain a spread original signal. The spread spectrum of signal code element by using pseudo-random code sequence is a general technique in the field of wideband spread spectrum communication technology, its action mechanism is that under the inherent chip rate a specific binary waveform which is easy to generate is produced, and the signal code element is matched by means of specific mode to spread signal frequency band, and because the pseudo-random code sequence rate is greater than signal code element rate, generally the pseudo-sequence code rate/signal code element rate is an integer far greater than 1, so that the signal gain after the spread spectrum treatment is far greater than 0.
In some preferred embodiments of this embodiment, the pseudo random code sequence used may be a GOLD sequence, fig. 3 shows a schematic diagram of constructing GOLD, specifically, two m sequences are first generated by a shift register with linear feedback, a GOLD sequence is obtained by modulo-2 addition of synchronization after the two m sequences are generated, a GOLD sequence is obtained by modulo-2 addition of the GOLD sequence and an original signal after the GOLD sequence is generated, and a spread original signal is obtained, fig. 4 shows autocorrelation and cross-correlation of GOLD sequences generated in the above embodiments, fig. 5 shows waveforms of original signals after GOLD spreading, as can be seen from fig. 4, the pseudo-random code sequence has both strong and weak cross-correlations, therefore, the spread original signal can be matched and synchronized through the sharp self-correlation peak after being transmitted in the underwater acoustic environment, so that accurate positioning can be realized.
After the spread original signal is obtained by the above embodiment, it is further required to perform differential phase shift keying modulation on the original signal by using a modulation signal to generate a transmission signal. The binary differential phase shift keying modulation is carried out on the code element signal, so that the phase ambiguity problem of the binary phase shift keying modulation can be avoided, and the signal code element synchronization during subsequent demodulation is facilitated. In a preferred embodiment of this embodiment, a sine wave with a frequency of 20KHZ is used as a modulation signal to perform phase shift keying modulation on a differential signal of a spread original signal to generate a transmission signal, and fig. 6 shows time domain and frequency domain waveforms of the transmission signal generated after the differential phase shift keying modulation.
Step S200 is a step of transmitting the transmission signal into the underwater acoustic environment, specifically, the transmission is performed by a transmission unit of the underwater acoustic baseline positioning system, and the transmission unit reads the transmission signal and transmits the transmission signal into the underwater acoustic environment through the FPGA transmission plate and the transducer.
Step S300 is a process of acquiring an effective signal and a frequency shift of a transmission signal after propagating through an underwater acoustic environment, and in some preferred embodiments of this embodiment, as shown in fig. 7, the method includes the following steps:
s310: continuously receiving an underwater acoustic signal using a receiving unit of the underwater acoustic baseline positioning system;
s320: calculating the frequency spectrum of the continuously received underwater sound signal in real time;
s330: searching the frequency spectrum of the continuously received underwater sound signal in the Doppler frequency shift searching range, judging whether a frequency peak exceeding a frequency peak detection threshold exists, if so, returning to the step S310, and if true, executing the step S340, wherein,
s340: and performing signal rollback and signal interception on the underwater sound signal with the true judgment result to obtain an effective signal, and calculating the difference value between the peak frequency of the effective signal and the peak frequency of the modulation signal to obtain the frequency correction value.
In some preferred embodiments of this embodiment, a transducer and an FPGA board of a receiving unit of an underwater acoustic baseline positioning system are used to continuously receive an underwater acoustic signal and perform real-time doppler search, specifically, the received underwater acoustic signal is subjected to analog-to-digital conversion, a real-time frequency spectrum of the received digital signal is obtained by performing real-time fourier transform, a doppler shift search range is set according to a modulation signal frequency, whether a frequency peak exceeding a frequency peak detection threshold exists in the real-time frequency spectrum is searched in the doppler shift search range (the frequency peak detection threshold is predetermined according to a performance parameter of the underwater acoustic baseline positioning system), if the frequency peak is found, signal rollback and signal interception are performed from a detected position, the intercepted signal is used as an effective signal which is received by the receiving unit after the intercepted signal propagates through an underwater acoustic environment, and then a difference between a peak frequency of the intercepted signal and a peak frequency of the modulation signal is calculated, using the frequency correction value as a frequency correction value; and if the underwater sound signal is not searched, continuously receiving the underwater sound signal and repeatedly searching. Fig. 8 shows a waveform of the effective signal acquired by the above embodiment.
Step S400 and step S500 are respectively used for generating a correlation detection signal and determining the arrival time of the effective signal through the sliding correlation detection of the correlation detection signal and the effective signal.
As described above, the arrival time of the effective signal can be accurately located by using the strong autocorrelation and the weak cross-correlation of the pseudo-random code, and the principle is that the modulation signal used in step S100 is used to perform differential phase shift keying modulation on the pseudo-random code sequence used in step S100 to obtain the correlation detection signal, the correlation detection signal is corrected by using the frequency correction value, the corrected correlation detection signal has strong autocorrelation and weak cross-correlation with the effective signal propagated through the underwater acoustic environment, and the correlation detection signal is used to perform sliding correlation detection with the effective signal, so that the accurate arrival time of the effective signal can be obtained.
Specifically, as shown in fig. 9, an initial value of the relative position of the correlation detection signal and the effective signal and a sliding step are set, then the correlation of the correlation detection signal and the effective signal is calculated and it is determined whether a predetermined correlation threshold (which is determined according to the nature of the spread spectrum signal used) is exceeded, if so, the position of the correlation detection signal relative to the effective signal is determined as the signal arrival time, and if not, the correlation detection signal is moved by the sliding step and the correlation is recalculated.
Fig. 10 is a result of sliding correlation detection of a correlation detection signal and an effective signal in a specific embodiment of this embodiment, which is different from a technique in the prior art that a carrier signal is demodulated first and then synchronized to perform positioning after a signal symbol is obtained, in this embodiment of the present application, correlation detection is directly performed on the modulated carrier signal, and arrival time of the effective signal is accurately positioned by using autocorrelation and cross-correlation characteristics of a pseudo-random code sequence included in the carrier signal.
Step S600 is a process of demodulating and despreading the effective signal to obtain an original signal, and includes the following steps: carrying out coherent demodulation processing on the effective signal based on the modulation signal to obtain a demodulated effective signal; sampling and judging the demodulated effective signal to obtain a judgment signal; de-spreading the decision signal based on the spread spectrum signal to obtain the original signal; acquiring the transmission time information based on the original signal.
Coherent demodulation method is a demodulation means for phase shift keying modulation, in particular for input signals
Comprises the following steps:
wherein,
is the number of the chips in the sequence,
for modulating signal frequency: a is the amplitude of the modulated signal,
is Gold chip. Using multiplier pairs
And filtering the high-frequency signal to obtain a demodulated signal, and performing sampling judgment on the demodulated signal to obtain a code element signal before modulation.
In some specific embodiments of this embodiment, coherent demodulation and sampling decision are performed on the effective signal by the coherent demodulation method based on the modulation signal in step S100, and fig. 11 shows a schematic diagram of coherent demodulation and sampling decision on the effective signal, where the sampling decision signal obtained after the above processing is the original signal after spreading.
The process of despreading the obtained decision signal is specifically to add the decision signal modulo 2 with the spread spectrum signal in step S100, and the obtained signal is the original signal. Fig. 12 shows an original signal waveform obtained by despreading the decision signal.
After the effective signal is demodulated and despread to obtain an original signal, based on the transmitting time information and the arrival time information of the effective signal, the propagation time of the transmitting signal in the underwater acoustic environment can be obtained, and further the distance information between the transmitting unit and the receiving unit is obtained through calculation. Ranging using the propagation time of a signal in an underwater acoustic environment is well known to those skilled in the art.
In order to verify the detection accuracy of the distance measurement method based on the underwater acoustic baseline positioning system, the method provided by the embodiment of the application is simulated, specifically, simulation calculation of effective signal arrival time detection is performed by modifying underwater acoustic channel parameters such as multipath delay and signal to noise ratio, wherein random numbers in a multipath delay setting range are grouped into 20 groups per signal to noise ratio, the detection result accuracy is tested, each group of experiment results is recorded, and the result is shown in fig. 13.
In fig. 13, the synchronization shift amount is an average shift amount with respect to the unit signal symbol width, the effective signal start position is calculated by the method of the present embodiment, and the average value of the deviation between the start position and the true value is determined as the synchronization shift amount. When the sound velocity is 1500m/s, the symbol width is 15cm, and the synchronization shift amount × the chip width is about the positioning accuracy. The statistical results of the experiments shown in fig. 13 show that the average offset of 100 experiments is 0.019 ± 0.045 chips, and the symbol synchronization positioning accuracy is 2.85 ± 6.75 mm.
While the present invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof as defined in the appended claims.
Claims (3)
1. A distance measurement method based on an underwater acoustic baseline positioning system is characterized by comprising the following steps:
s100: determining a transmitting signal corresponding to an original signal based on a preset spread spectrum signal and a preset modulation signal, wherein the original signal comprises transmitting time information, the spread spectrum signal is a GOLD sequence in a pseudo-random code sequence, and the modulation signal is a sine wave with the frequency of 20 KHZ;
s200: transmitting the transmit signal into an underwater acoustic environment using a transmit unit of the underwater acoustic baseline positioning system;
s300: determining a valid signal and a frequency correction value from an underwater sound signal continuously received by a receiving unit of the underwater sound baseline positioning system, wherein the valid signal is a signal received by the receiving unit after the transmitting signal propagates through an underwater sound environment, and the frequency correction value is determined based on the modulation signal and the valid signal;
s400: determining a correlation detection signal based on the spread spectrum signal, the modulation signal and the frequency correction value;
s500: performing sliding correlation detection on the effective signal based on the correlation detection signal, and determining arrival time information of the effective signal;
s600: acquiring the transmission time information based on the modulation signal, the spread spectrum signal and the effective signal, and determining the propagation time of the transmission signal and the distance from the transmitting unit to the receiving unit based on the transmission time information and the arrival time information;
the step S100 of determining a transmission signal corresponding to the original signal based on the spread spectrum signal and the modulation signal further includes the following steps:
spreading the original signal by using the spread spectrum signal to obtain a spread spectrum original signal;
carrying out differential phase shift keying modulation on the spread original signal by using the modulation signal to obtain the transmitting signal;
the step S400 further includes the steps of:
carrying out differential phase shift keying modulation on the spread spectrum signal by using the modulation signal to obtain a correlation detection signal;
performing frequency correction on the correlation detection signal by using the frequency correction value;
the step S500 further includes the steps of:
s510: setting an initial value and a sliding step length of a relative position of the correlation detection signal and the effective signal;
s520: calculating a correlation of the correlation detection signal and the valid signal;
s530: judging whether the correlation exceeds a correlation threshold value, if the judgment result is false, executing step S540, returning to execute step S520, if the judgment result is true, executing step S550, wherein,
s540: resetting the relative position of the correlation detection signal and the effective signal according to the sliding step length;
s550: determining the arrival time of the effective signal according to the position of the correlation detection signal relative to the effective signal when the judgment result is a true value;
the correlation threshold is determined based on a property of the spread spectrum signal;
in the step S600, the obtaining the transmission time information based on the modulation signal, the spread spectrum signal and the effective signal further includes the following steps:
carrying out coherent demodulation processing on the effective signal based on the modulation signal to obtain a demodulated effective signal;
sampling and judging the demodulated effective signal to obtain a judgment signal;
de-spreading the decision signal based on the spread spectrum signal to obtain the original signal;
acquiring the transmission time information based on the original signal.
2. The range finding method based on the underwater acoustic baseline positioning system as claimed in claim 1, wherein the step S300 of determining the effective signal and the frequency correction value from the underwater acoustic signal continuously received by the receiving unit of the underwater acoustic baseline positioning system further comprises the following steps:
s310: continuously receiving an underwater acoustic signal using a receiving unit of the underwater acoustic baseline positioning system;
s320: calculating the frequency spectrum of the continuously received underwater sound signal in real time;
s330: searching the frequency spectrum of the continuously received underwater sound signal in the Doppler frequency shift searching range, judging whether a frequency peak exceeding a frequency peak detection threshold exists, if so, returning to the step S310, and if true, executing the step S340, wherein,
s340: and performing signal rollback and signal interception on the underwater sound signal with the true judgment result to obtain an effective signal, and calculating the difference value between the peak frequency of the effective signal and the peak frequency of the modulation signal to obtain the frequency correction value.
3. The distance measurement method based on the underwater acoustic baseline positioning system as claimed in claim 2, wherein:
the doppler shift search range is determined based on the modulation signal, and the frequency peak detection threshold is determined based on performance of the underwater acoustic baseline positioning system.
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