Probe-through integration-oriented hyperbolic frequency modulation sonar signal design and processing method

Abstract

A hyperbolic frequency modulation sonar signal designing and processing method oriented to detection and communication integration comprises the following steps: generating a group of orthogonal HFM element waveforms including a sensing preamble for detection, an upper frequency sweeping HFM waveform and a lower frequency sweeping HFM waveform; communication data is modulated in a UDK mode, and element waveforms are spliced according to a sending data sequence to form a communication data stream. And then, the HFM-UDK signal is transmitted after being subjected to quadrature modulation. At a receiving end, echo signals are collected, and orthogonal demodulation, low-pass filtering, downsampling and other preprocessing are carried out. And finally, performing parallel detection imaging and communication demodulation processing on the preprocessed complex baseband signal flow: realizing high-resolution spectral analysis of a detection link through Zoom-FFT, and generating a two-dimensional sonar image in combination with beam forming. A communication link positions a sensing lead code through matched filtering so as to determine a frame header, and then a parallel matched filtering structure is adopted to demodulate and judge a communication symbol. According to the invention, cooperative work of detection and communication functions is realized, and the performance of the system in a high-speed motion environment is remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of digital signal processing and underwater detection communication, and relates to a sonar signal design and processing method, in particular to a joint design method of hyperbolic frequency modulation sonar signal and processing for detection integration, and a corresponding signal processing method and system. BACKGROUND

[0002] Sonar is an electronic device that uses sound waves in underwater media for detection, navigation, positioning and communication. It is the most widely used and most important technical device in underwater acoustics. The working principle of the sonar system is to transmit acoustic signals or only receive acoustic signals in the environment, and analyze the signals detected by the sensor through electro-acoustic conversion and information processing, to complete the measurement task of the distance, dynamic or characteristics of the underwater target. According to the direction of the sound beam coverage and the function, the sonar can be divided into forward-looking sonar, side-scan sonar, downward-looking sonar and other types. However, the core function of the existing sonar is mainly concentrated in target detection and imaging. If the demand for underwater acoustic communication is to be met, an independent communication logic usually needs to be designed additionally, which has limitations in high-integration requirement scenarios. In order to overcome the limitations of the existing sonar system in single function and low integration, the sonar detection integration signal emerges as the times require.

[0003] The sonar detection integration signal is a signal design that simultaneously has the functions of target detection and communication in the same acoustic carrier. In the detection phase, the sonar performs digital signal processing on the echo signal, and at the same time combines the beam forming algorithm to efficiently obtain the key detection information such as the angle and distance of the underwater target. In terms of communication, the signal carries data through modulation in the transmission stage, propagates through sound waves and extracts the communication content after demodulation by the receiving end. Through the design of special signal waveforms, modulation schemes and matched filters and other signal processing means, the signal can simultaneously have the two core functions of detection and communication. At present, the signal has been widely used in unmanned underwater vehicles, ocean environment monitoring and resource exploration, submarine communication, underwater cooperative forward-looking and other scenarios.

[0004] Signal modulation and matched demodulation are core components of integrated sonar detection and communication. Linear Frequency Modulation (LFM) signals are among the most common modulation signals. By combining them with pulse compression algorithms, their broadband characteristics can be effectively utilized to achieve high range resolution. However, when processing echoes from high-speed moving targets or platforms, LFM signals are susceptible to Doppler effects and noise, leading to a decline in pulse compression performance. Hyperbolic Frequency Modulation (HFM) signals, compared to traditional LFM signals, offer superior Doppler and noise tolerance, exhibiting less performance loss in complex underwater environments. Similar to LFM signals, HFM signals also rely on matched filtering for pulse compression to obtain fine range resolution. To load digital information onto these frequency-modulated signals, a common and robust method is Up / Down Keying (UDK). This method uses upward and downward sweeping pulses to represent different data bits. Because of the good orthogonality between the up-frequency and down-frequency waveforms, the receiver can easily distinguish them using parallel matched filters, thus achieving simple and reliable demodulation. The hyperbolic frequency modulation up-down-keying (HFM-UDK) signal, which combines HFM and UDK modulation, can be used simultaneously for forward-looking sonar target detection and communication needs, allowing the system to achieve coordinated operation of detection and communication functions without increasing complexity or cost. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing technologies and provide a hyperbolic frequency modulated sonar signal design and processing method for integrated exploration and communication.

[0006] The primary objective of this invention is to address the severe performance degradation of existing sonar systems in complex underwater environments by combining HFM signals with UDK modulation, which maintains these characteristics. Secondly, by introducing Zoom-FFT technology, this invention enables efficient high-resolution analysis of preset key frequency bands in the received signal, thereby accurately obtaining the FFT values ​​of each array data element at key frequency points. This invention aims to provide a high-performance integrated sonar system solution that features non-interference between detection and communication functions, a simple demodulation process, and robust operation in complex marine environments.

[0007] To address the aforementioned technical problems, the first aspect of this invention relates to a method for designing and processing hyperbolic frequency-modulated sonar signals for integrated exploration and communication, taking a forward-looking sonar as an example, and includes the following steps: S1. Generate a set of orthogonal HFM primitive waveforms, including a sensing preamble for detection. And two waveforms with opposite sweep directions: the upper sweep HFM waveform. and downsweep HFM waveform .

[0008] S2. The communication data is modulated using the UDK method, resulting in the final communication data stream. It is a sequence of transmitted data based on the aforementioned primitives. A signal pieced together.

[0009] S3, HFM-UDK signal After being orthogonally modulated, it is transmitted through the transmitting transducer of the forward-looking sonar.

[0010] S4. Acquire raw echo signals from the forward-looking sonar to obtain raw echo data. .

[0011] S5. Preprocess the raw data collected from each array element, including orthogonal demodulation, low-pass filtering, downsampling, etc., to obtain... .

[0012] Wherein, the carrier frequency is assumed to be Then, after quadrature demodulation, the center frequency of the original signal is shifted to 0 and 1. The low-pass filter removes high-frequency components generated during demodulation and downsamples the filtered signal to reduce the number of data points without distortion, thereby effectively reducing the complexity of subsequent calculations.

[0013] S6. Perform parallel detection imaging and communication demodulation processing on the received and preprocessed complex baseband signal stream. This process includes: S61, Detection and Imaging Link: Perform Zoom-FFT processing on the metadata of each array to obtain the frequency points. k Data vectors on Then, the data at each frequency point are weighted and summed using a beamforming algorithm to form a beam pointing in a specific direction. beam Finally, the processed energies at different frequencies are superimposed to obtain the range-intensity information in each beam direction, and the data from all beams are combined to form the final two-dimensional sonar image.

[0014] S62, Communication Demodulation Link: Communication utilizes three array elements for simultaneous demodulation. The first step in demodulation is to determine the precise start time of the communication data stream. This is achieved by searching the received signal for the sensing preamble defined in step S1. Assume the reference preamble sequence is... The processed received signal sequence is then subjected to matched filtering with the reference preamble sequence to obtain the correlation output sequence. This allows the frame header position to be located. After determining the start of the data, the receiver begins demodulating the subsequent communication data symbols one by one. This process employs a parallel matched filter structure, processing each received symbol... The decision is made by matching the waveform with the frequency rise and fall template to obtain the result. and A decision maker compares the peak output energy of two filters. and Based on the waveform corresponding to the higher energy level, the bits carried by that symbol are determined. .

[0015] Furthermore, if the sum of the outputs of the three array element decision controllers is greater than or equal to 2, then the decision result is... The value is 1 if the condition is true and 0 otherwise.

[0016] A second aspect of the present invention relates to a hyperbolic frequency modulated sonar signal processing device for integrated exploration and communication, comprising a memory and one or more processors, wherein the memory stores executable code, and the one or more processors execute the executable code to implement a hyperbolic frequency modulated sonar signal design method for integrated exploration and communication according to the present invention.

[0017] A third aspect of the invention relates to a computer-readable storage medium having a program stored thereon, which, when executed by a processor, implements a hyperbolic frequency modulated sonar signal design method for integrated exploration and communication according to the present invention.

[0018] The working principle of this invention is as follows: by combining HFM waveforms with UDK modulation, the same acoustic signal can simultaneously possess detection and communication capabilities. The transmitting end first generates a preamble, up-frequency and down-frequency HFM primitives, and then concatenates them into an HFM-UDK signal based on the data bit sequence before transmission. The receiving end performs orthogonal demodulation and downsampling on the multi-element echo, before sending it to the detection link and communication link respectively. The detection link uses Zoom-FFT to extract key frequency band features and performs beamforming in the frequency domain to obtain a high-resolution two-dimensional sonar image. The communication link uses matched filtering to search for the preamble to locate the frame header and performs up- / down-frequency energy decision for each symbol, using multi-element majority voting to improve demodulation reliability. The two links operate in parallel, achieving synchronous detection and communication under a unified signal.

[0019] The innovation of this invention lies in the deep integration of the HFM waveform, which exhibits strong Doppler robustness, with the structurally simple and orthogonally sound UDK modulation, enabling stable detection and communication functions on a single acoustic carrier. Simultaneously, synchronization and decision accuracy are improved through frequency band allocation and matched filtering. Furthermore, Zoom-FFT is used instead of the traditional full-bandwidth FFT, significantly reducing computational load and improving key frequency band resolution. The combination of multi-frequency beamforming and a three-element majority voting strategy ensures high reliability for both imaging and communication in complex underwater environments.

[0020] The present invention has the following beneficial effects: 1. Applying the HFM waveform and UDK modulation method, which have excellent environmental adaptability, to forward-looking sonar gives the signal strong anti-noise and anti-Doppler characteristics at the transmitting end, significantly improving the system's performance in complex underwater environments.

[0021] 2. The FFT algorithm is optimized by introducing Zoom-FFT technology for high-resolution analysis of key frequency bands. Compared with traditional large-scale FFT methods, it can effectively reduce computational complexity, save resource consumption and costs without sacrificing frequency resolution, and is especially suitable for hardware platforms with high real-time requirements. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the signal generation and transmission process of the present invention.

[0023] Figure 2 This is a schematic diagram of the optimized imaging algorithm of the present invention.

[0024] Figure 3 This is a flowchart of the communication demodulation algorithm of the present invention.

[0025] Figure 4 This is a schematic diagram of the structure of the device of the present invention. Detailed Implementation

[0026] To better understand the above technical solution, the technical solution will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0027] Example 1

[0028] This embodiment relates to a hyperbolic frequency modulated sonar signal design and processing method for integrated exploration and communication. Taking a forward-looking sonar as an example, the implementation process specifically includes the following steps: S1. Generate a set of orthogonal HFM primitive waveforms, including a sensing preamble for detection. And two waveforms with opposite sweep directions: the upper sweep HFM waveform. and downsweep HFM waveform .

[0029] For a duration of T The starting frequency is Termination frequency is The HFM pulse, at time instantaneous frequency f(t) It can be given by the following formula:

[0030] in, For signal bandwidth, The center frequency of the baseband signal. It is a parameter that controls the shape of the hyperbolic sweep frequency.

[0031] Phase of the signal Obtained by integrating the instantaneous frequency:

[0032] Finally, the generated complex baseband HFM waveform The expression is:

[0033] Select the start frequency and end frequency of the frame header as follows: and The start and end frequencies of the data section are: and Therefore, the bandwidth occupied by the frame header and the bandwidth occupied by the data are respectively:

[0034] Distributing the frame header and data in different frequency bands, i.e.

[0035] S2, such as Figure 1 As shown, the communication data is modulated using the UDK method, and the final generated communication data stream It is a sequence of transmitted data based on the aforementioned primitives. A signal pieced together.

[0036] Specifically, sending sequence Complete communication data stream This can be represented as the weighted sum of the time-shifted primitive waveforms over all symbol periods, based on the above coefficients:

[0037] in, and These are the up-frequency and down-frequency HFM primitive waveforms generated in step one, respectively. The duration of a single symbol, n This is the index of the symbol sequence. This formula precisely describes the process of selecting and splicing the corresponding HFM waveform bit by bit according to the data sequence to generate the final communication data stream.

[0038] S3, HFM-UDK signal After being orthogonally modulated, it is transmitted through the transmitting transducer of the forward-looking sonar.

[0039] Complex baseband signal Decomposed into in-phase components and orthogonal components ,Right now Then, With carrier components Multiply, carrier signal with a phase difference of 90° Multiply the two signals and then add them together to obtain the final passband real signal. .

[0040]

[0041] S4. Acquire raw echo signals from the forward-looking sonar to obtain raw echo data. .

[0042] S5. Preprocess the collected raw data, that is, compare it with the center frequency. Multiplying the orthogonal bases yields in-phase components. I [ m and orthogonal components Q [ m The complex domain signal is converted into two real domain signals for processing.

[0043] in, It is the system's sampling frequency; this process shifts the signal spectrum to 0 and... nearby.

[0044] Subsequently, and The two sequences are each subjected to digital low-pass filtering to remove high-frequency components generated by demodulation and suppress out-of-band noise. The resulting two sequences are as follows: and .

[0045] Finally, the two filtered signals are factored... D Extract the data to reduce the data rate to the sampling rate required for subsequent processing. The final output discrete complex baseband signal is

[0046] S6. Perform parallel detection imaging and communication demodulation processing on the received and preprocessed complex baseband signal stream. This process includes the following two parallel links: S61, Detection Imaging Link: This link is designed to generate high-resolution sonar images. For example... Figure 2 As shown, this process uses Zoom-FFT on the complex baseband signal. Perform high-resolution spectrum analysis to obtain complex data focused on the key frequency band of the baseband signal. The complex data is obtained by means of... implement N The point FFT is used to obtain the corresponding physical frequency point. Determined by the following formula:

[0047] in, For 0-centered FFT frequency index,

[0048] This high-resolution transformation allows for the precise acquisition of key frequency points. k Complex data vectors on .in:

[0049] Subsequently, a frequency domain beamforming algorithm is applied to the data at each frequency point, by beamforming with a beam pointing in a specific direction. The guide vector conduct Z The weighted summation of each array element forms a single-band beam output. :

[0050] The beam data from each frequency band are superimposed to obtain the beam strength output for a single beam angle:

[0051] Will l From one angle, v The final range-angle intensity matrix can be obtained by combining the beam intensity outputs at each distance:

[0052] S62, Communication Demodulation Link: Communication utilizes three array elements for simultaneous demodulation. For example... Figure 3 As shown, in the initial stage of demodulation, the starting position of the data stream is located, a task accomplished through matched filtering. Let the reference preamble sequence be... The impulse response of the matched filter This refers to the time deconvolution conjugate of the preamble. The matched filtering process involves comparing the received signal sequence with... Perform convolution operations to obtain the correlation output sequence. :

[0053] By detecting the relevant output sequence The peak position can be used to locate the beginning position of the data.

[0054] After determining the start position of the data, the receiver begins demodulating the subsequent communication data symbols one by one. This process employs a parallel matched filter structure, processing each received symbol... A judgment will be rendered.

[0055] Specifically, receiving symbols It is simultaneously fed into two complex matched filters to match the upper sweep template. and downscan frequency template ,in and These are signal templates and Time-conjugated conjugate, complex output of two filters and They are:

[0056] A decision maker compares the peak values ​​of the output energies of two filters. and :

[0057] Based on the waveform corresponding to the higher energy level, the data bits carried by that symbol are determined.

[0058] Finally, the data bits are determined by equation (21).

[0059]

[0060] Example 2

[0061] like Figure 4As shown, this embodiment relates to a hyperbolic frequency modulated sonar signal processing device for integrated exploration and communication, including a memory and one or more processors. The memory stores executable code, and when the one or more processors execute the executable code, it is used for a hyperbolic frequency modulated sonar signal design method for integrated exploration and communication as described in Embodiment 1.

[0062] Example 3

[0063] This embodiment relates to a computer-readable storage medium storing a program that, when executed by a processor, implements a hyperbolic frequency modulated sonar signal design method for integrated exploration and communication as described in Embodiment 1.

[0064] Finally, it should be noted that the specific solutions and embodiments described above in conjunction with the figures are only a preferred embodiment of the present invention. Those skilled in the art can make some changes and modifications to the described technical content without departing from the technical scope of the present invention. However, any modifications and variations made without departing from the spirit and principle of the present invention should fall within the scope of the technical solution of the present invention.

Claims

1. A method for signal design and processing of a sounding-integrated hyperbolic frequency modulation (HFM) sonar, characterized in that, The method comprises the following steps: S1. Generating a set of orthogonal HFM elementary waveforms, including one sensing preamble and two waveforms with opposite sweep directions: an up-sweep HFM waveform and a down-sweep HFM waveform ; S2, the communication data is modulated by UDK mode, and the final generated communication data stream is a signal spliced by the above-mentioned base elements according to the transmission data sequence ​ S3, the HFM-UDK signal after being quadrature modulated by the transmit transducer of the forward-looking sonar S4, collect the front-looking sonar raw echo signal to obtain raw echo data ; S5、 The raw data collected by each array element is preprocessed, including quadrature demodulation, low-pass filtering, and down-sampling, to obtain ; Wherein, assuming the signal center frequency is , the center frequency of the original signal after quadrature demodulation is moved to 0 and , the low-pass filter filters out the high-frequency components generated in the demodulation process, and the filtered signal is down-sampled to reduce the number of data points without distortion, thereby effectively reducing the complexity of subsequent operations; S6, performing parallel sounding imaging and communication demodulation processing on the received and pre-processed complex baseband signal stream, the process comprising: S61, probe imaging: Zoom-FFT processing is performed on each array element data to obtain data vectors on each frequency point k , then the data of each frequency point is weighted and summed by using beam forming algorithm to form a beam pointing to a specific direction ; finally, the energy of different frequency points after processing is superimposed to obtain distance-intensity information in each beam direction, and the data of all beams are collected to form the final two-dimensional sonar image;​​ S62. Communication Demodulation: Communication utilizes three array elements for simultaneous demodulation; the first step in demodulation is to determine the precise start time of the communication data stream; this is achieved by searching for the sensing preamble defined in step S1 in the received signal; assuming the reference preamble sequence is... The processed received signal sequence is then subjected to matched filtering with the reference preamble sequence to obtain the correlation output sequence. This allows the frame header position to be locked; after determining the start position of the data, the receiver begins to demodulate the subsequent communication data symbols one by one; this process uses a parallel matched filter structure for each received symbol. The decision is made by matching the waveform with the frequency rise and fall template to obtain the result. and A decision maker compares the peak output energy of two filters. and Based on the waveform corresponding to the higher energy level, the bits carried by that symbol are determined. If the sum of the outputs of the three array element decision controllers is greater than or equal to 2, then the decision result is... The value is 1 if it is not 1, otherwise the value is 0.

2. The method of claim 1, wherein, In the step S1, a set of orthogonal HFM basis waveforms is first generated for an HFM pulse with a duration T , a start frequency , and an end frequency , the instantaneous frequency at time f ( t ) is given by wherein, is the signal bandwidth, is the baseband signal center frequency, is a parameter controlling the hyperbolic sweep shape; Phase of the signal Obtained by integrating the instantaneous frequency: Finally, the resulting complex baseband HFM waveform The expression is: The communication uses UDK coding, the communication data stream finally generated in step S2 is a signal spliced from the above-mentioned base elements according to the transmission data sequence ​ wherein, and are the up- and down-converted HFM primitive waveforms generated in step one, respectively, is the duration of a single symbol, n is the index of the symbol sequence.

3. The method of claim 1, wherein, The probe imaging of step S6 specifically includes, for each array element i The collected echo signals are preprocessed, which includes orthogonal demodulation with a center frequency of f0 , low-pass filtering, and down-sampling by a factor of M D to obtain a complex baseband signal ; The complex baseband signal was processed using Zoom-FFT. Perform high-resolution spectrum analysis to obtain complex data focused on the key frequency band of the baseband signal. The complex data is obtained by means of... implement N The point FFT is used to obtain the corresponding physical frequency point. Determined by the following formula: wherein, is the sampling frequency of the system, is the FFT frequency index centered at 0, By this high resolution transform, the complex data vector on each key frequency point can be accurately obtained k ; wherein:​ Subsequently, a beam forming algorithm is applied to the data of each frequency bin, by performing a weighted summation over the elements with a steering vector pointing in a specific direction M forming a beam output for the single frequency band :​​ Superimposing the beam data of each frequency band to obtain a beam intensity output of a beam angle: The beam intensity output of the combination of the l angles, v distances can be combined to obtain the final range-angle intensity matrix: 。 4. The signal communication demodulation algorithm for sounding and integration-oriented dual hyper-frequency modulation sonar according to claim 1, characterized in that, The communication demodulation of step S6 specifically includes, in the beginning stage of demodulation, locating the starting position of the data stream by matched filtering; if the reference preamble sequence is set as the impulse response of the matched filter is the time deconvolution conjugate of the preamble; The matched filter process is to convolve the received signal sequence with the known sequence, thereby obtaining a correlation output sequence : By detecting the peak position of the relevant output sequence the start position of the data can be located; After determining the data start position, the receiver begins to demodulate the subsequent communication data symbols one by one; this process uses a parallel matched filter structure to make a decision for each received symbol .

5. The signal communication demodulation algorithm for sounding and integration-oriented dual hyperbolic frequency modulation sonar according to claim 4, characterized in that, making a decision for each received symbol includes receive symbols are simultaneously fed into two complex matched filters to match the up-chirp template and the down-chirp template where and are the time deconvolution conjugates of the signal templates and The complex outputs of the two filters and are respectively: comparing the peak values of the two filter output energies by a decision device and : And according to the waveform corresponding to the higher energy, the data bits carried by the symbol are judged Finally, the data bits are judged by formula (21): 。 6. The method of claim 1, wherein, In step S62, if the sum of the outputs of the three array element deciders is equal to or greater than 2, the decision result is 1, and otherwise the decision is 0. is 1, and otherwise the decision is 0.

7. A hyperbolic frequency-modulated sonar signal processing device oriented to sounding integration, characterized by The device comprises a memory and one or more processors, the memory stores executable code, and the one or more processors execute the executable code to implement the method for designing and processing a hyperbolic frequency modulation sonar signal for sounding integration according to any one of claims 1-6.

8. A computer-readable storage medium, characterized in that, The device has a program stored thereon, and the program is executed by a processor to implement the method for designing and processing a hyperbolic frequency modulation sonar signal for sounding integration according to any one of claims 1-6.

Images