CN-122017814-A - Multi-parameter modulation sonar waveform design method based on pulse width Costas coding, sonar detection system and computer readable storage medium

CN122017814ACN 122017814 ACN122017814 ACN 122017814ACN-122017814-A

Abstract

The application provides a pulse width Costas coding-based multiparameter modulation sonar waveform design method, a sonar detection system and a computer readable storage medium, relating to the technical field of underwater acoustic signal processing and waveform design, comprising system initialization and global parameter configuration; the method comprises the steps of constructing a non-uniform time structure and pulse width codes, outputting pulse width of sub-pulses and absolute starting time of the sub-pulses on a time axis, generating a frequency code sequence, a phase code sequence and a slope code sequence, constructing a multi-dimensional orthogonal modulation parameter space, outputting complex baseband waveforms of the sub-pulses based on global parameters, the pulse width of the sub-pulses and the multi-dimensional orthogonal modulation parameter space in combination with an adaptive slope adjustment strategy, and performing time domain waveform synthesis based on the absolute starting time of the sub-pulses on the time axis and the complex baseband waveforms of the sub-pulses to obtain multi-parameter modulation sonar waveforms based on pulse width Costas codes. The application converts the periodic high grating lobes into low-level background noise by constructing a non-uniform time structure.

Inventors

LOU YI
CHEN ZHIKUAN
ZHOU ZHIQUAN
ZHAO YUNJIANG
ZHOU ZEMIN

Assignees

哈尔滨工业大学（威海）

Dates

Publication Date: 20260512
Application Date: 20260409

Claims (10)

1. The multiparameter modulation sonar waveform design method based on pulse width Costas coding is characterized by comprising the following steps of: carrying out system initialization and global parameter configuration, wherein the global parameters comprise the total duration of waveforms, the total bandwidth of transmitting signals, the dividing number of sub-pulses and the sampling rate of digital signal processing of a sonar detection system; Constructing a non-uniform time structure and pulse width codes based on the total duration of the waveform and the dividing number of the sub-pulses, and outputting the pulse width of the sub-pulses and the absolute starting time of the sub-pulses on a time axis; Generating a frequency code sequence, a phase code sequence and a slope code sequence, and constructing a multidimensional orthogonal modulation parameter space by combining the dividing number of sub-pulses, the total bandwidth of a transmitting signal and the pulse width of the sub-pulses; outputting complex baseband waveforms of the sub-pulses based on the global parameters, the pulse widths of the sub-pulses and the multi-dimensional orthogonal modulation parameter space in combination with the adaptive slope adjustment strategy; and carrying out time domain waveform synthesis based on the absolute starting time of the sub-pulse on a time axis and the complex baseband waveform of the sub-pulse to obtain the multiparameter modulated sonar waveform based on pulse width Costas coding.
2. The multi-parameter modulation sonar waveform design method based on pulse width Costas code of claim 1, wherein the constructing the non-uniform time structure and the pulse width code comprises: selecting a Costas sequence with the order of N as a pulse width coding sequence; summing the Costas sequences to obtain a total sequence weight; Mapping the discrete integer sequence into continuous time amounts by using a normalization factor, and calculating pulse widths of the sub-pulses; the absolute starting moment of the sub-pulses on the transmission time axis is calculated recursively on the basis of the pulse width of the respective sub-pulse.
3. The pulse width Costas recited in claim 1, wherein the constructing the multi-dimensional orthogonal modulation parameter space comprises: Generating frequency-coded sequences using Costas sequences, sequence elements Deriving each sub-pulse center frequency based on: ; In the formula, The baseband center frequency of the nth sub-pulse, In order to be able to start the frequency, For frequency hopping step length, take Wherein B represents the total bandwidth of the transmitted signal, and N represents the dividing number of the sub-pulses; Generating phase-coded sequences using pseudorandom binary sequences Sequence elements ; Generating slope coding sequences using pseudo-random binary sequences Sequence elements ; Thereby obtaining four-dimensional modulation parameter vector in the multi-dimensional orthogonal modulation parameter space , Representing the pulse width of the nth sub-pulse.
4. The method for designing a multiparameter modulated sonar waveform based on pulse width Costas code of claim 3, wherein said complex baseband waveform of said sub-pulses Expressed as: ; In the formula, A rectangular window function, indicating that the sub-pulses have values only in local time, t indicates a global continuous time variable, Representing the phase encoded value; representing the chirp rate of the nth sub-pulse, Representing a natural exponential function, j being an imaginary unit; The frequency modulation slope of the nth sub-pulse The adaptive dynamic adjustment strategy of (1) is: Setting the target effective bandwidth of each sub-pulse to be There is Or (b) ; According to the pulse width of the current sub-pulse Calculating the absolute value of the frequency modulation slope ; Combining slope coding sequences Determining slope polarity, final chirp rate The calculation formula of (2) is as follows: 。
5. the pulse width Costas recited in claim 1, wherein the time domain waveform synthesis has the following specific expression: ; Wherein the method comprises the steps of Indicating that the nth sub-pulse is delayed on the time axis The waveform is The total energy E normalization process of (1) satisfies: ; the waveform also comprises a windowing step before transmission, and the whole waveform is provided with the waveform A smoothing window function is applied across the head and tail of (a).
6. The pulse width Costas recited in claim 1, further comprising the step of performing matched filtering processing on the echo signal at the receiving end: And completely reproducing a multiparameter modulated sonar waveform based on pulse width Costas coding at a receiving end as a local reference signal, constructing a matched filter with impulse response being the conjugate inversion of the local reference signal, and carrying out convolution on an echo signal acquired by the receiving end and the impulse response to complete matched filter operation.
7. The method for designing a multiparameter modulated sonar waveform based on pulse width Costas code of claim 2, wherein the Costas sequence has an order N in the range of And N is a prime number or a power of prime number minus 1.
8. The pulse width Costas in claim 4, wherein the sub-pulse bandwidth is The setting of (2) is also such that if the sub-pulse spectra do not overlap in the frequency domain, then If the sub-pulse frequency spectrum is allowed to be partially overlapped in the frequency domain to improve the frequency spectrum utilization rate, then 。
9. A sonar detection system, comprising: The waveform generation module is configured with a memory and a processor, wherein the memory stores a computer program, and the processor realizes the multiparameter modulation sonar waveform design method based on pulse width Costas coding according to any one of claims 1-8 when executing the computer program to generate digital baseband waveform data; the digital-to-analog conversion module is used for converting the digital baseband waveform data into analog electric signals; the transmitter module is used for carrying out power amplification and carrier modulation on the analog electric signal and driving the underwater acoustic transducer to transmit sound waves to the underwater; the receiver module is used for receiving echo signals reflected by the underwater target and preprocessing the echo signals; and the signal processing module is used for carrying out matched filtering and Doppler compensation processing on the received echo signals and the locally stored reference waveforms and extracting the distance and speed information of the target.
10. A computer readable storage medium having stored thereon a computer program, which when executed by a processor implements a pulse width Costas code based multiparameter modulated sonar waveform design method as defined in any one of claims 1-8.

Description

Multi-parameter modulation sonar waveform design method based on pulse width Costas coding, sonar detection system and computer readable storage medium Technical Field The application relates to the technical field of underwater acoustic signal processing and waveform design, in particular to a multiparameter modulation sonar waveform design method based on pulse width Costas coding, a sonar detection system and a computer readable storage medium. Background In the field of active sonar detection, particularly target detection and identification for shallow sea environments, extremely serious challenges are faced. Shallow sea channels have complex boundary conditions, and reflection from the sea surface to the sea floor causes severe multipath effects, which in turn produce strong reverberation disturbances. Reverberation typically appears as colored noise associated with the transmitted signal, which tends to be much stronger than ambient noise, and is a major bottleneck limiting shallow sea sonar detection performance. In order to effectively detect a target in a strong reverberant background, a transmit waveform must have extremely high signal processing gain and excellent sidelobe suppression capability. Existing sonar waveform designs, such as Linear Frequency Modulation (LFM) signals and their derived waveforms (e.g., pulse trains, conventional code modulation waveforms, etc.), although solving the problem of distance and speed resolution to some extent, still have significant drawbacks. First, conventional burst waveforms typically employ a uniform time-slicing strategy, and this strictly periodic structure inevitably introduces periodic grating side lobes (Grating Lobes) of high amplitude in the blurring function. Under the influence of strong direct waves or strong target echoes, the high side lobes are very easy to cover adjacent weak targets, so that the phenomenon of 'black under the lamp' is caused. Secondly, the existing multi-parameter modulation method often has difficulty in combining time-frequency resolution and side lobe level, and especially when facing to shallow sea complex multipath environment, single-dimension parameter coding (such as frequency or phase coding only) lacks enough freedom degree to resist variable channel interference, so that the anti-reverberation capability of the system is insufficient. Therefore, aiming at the detection requirement of the strong reverberation environment of the shallow sea, the periodic constraint of the traditional waveform design is urgently required to be broken, and a novel sonar waveform design method capable of simultaneously realizing ultra-low range side lobes, high Doppler resolution and strong reverberation resistance is developed. Disclosure of Invention In order to solve the problems, the technical scheme adopted by the application is a multiparameter modulation sonar waveform design method based on pulse width Costas coding, which comprises the following steps: Carrying out system initialization and global parameter configuration, wherein the global parameters comprise the total waveform duration, total transmitting signal bandwidth, sub-pulse dividing number and sampling rate of digital signal processing of a sonar detection system; Constructing a non-uniform time structure and pulse width codes based on the total duration of the waveform and the dividing number of the sub-pulses, and outputting the pulse width of the sub-pulses and the absolute starting time of the sub-pulses on a time axis; Generating a frequency code sequence, a phase code sequence and a slope code sequence, and constructing a multidimensional orthogonal modulation parameter space by combining the dividing number of sub-pulses, the total bandwidth of a transmitting signal and the pulse width of the sub-pulses; outputting complex baseband waveforms of the sub-pulses based on global parameters, pulse widths of the sub-pulses and a multi-dimensional orthogonal modulation parameter space in combination with an adaptive slope adjustment strategy; and carrying out time domain waveform synthesis based on the absolute starting time of the sub-pulse on a time axis and the complex baseband waveform of the sub-pulse to obtain the multiparameter modulated sonar waveform based on pulse width Costas coding. Optionally, constructing the non-uniform temporal structure and pulse width coding includes: selecting a Costas sequence with the order of N as a pulse width coding sequence; summing the Costas sequences to obtain a total sequence weight; Mapping the discrete integer sequence into continuous time amounts by using a normalization factor, and calculating pulse widths of the sub-pulses; the absolute starting moment of the sub-pulses on the transmission time axis is calculated recursively on the basis of the pulse width of the respective sub-pulse. Optionally, constructing the multidimensional orthogonal modulation parameter space includes: Generating frequency-coded sequence