Underwater acoustic pulse echo ranging method based on time reversal

Abstract

The invention provides an underwater acoustic pulse echo ranging method based on time reversal, and the method comprises the steps: estimating the time delay of each path of a multipath channel, and obtaining and designing a virtual channel; enabling the received signal to pass through a virtual channel, and eliminating a received signal time expansion phenomenon caused by a multipath effect; intercepting a side peak component of the time reversal output signal through an adaptive energy windowing algorithm, and extracting a focusing peak of the signal; carrying out correlation processing on the windowed signal and the transmitted signal to find the accurate arrival time of the received signal, the difference between the signal arrival time and the signal transmitting time is the underwater propagation duration of the signal, and finally, measuring the distance between the ranging system and a target by using an acoustic propagation formula. According to the invention, signal distortion caused by the multipath effect is eliminated, the accuracy of extracting the target echo arrival time is improved, and the ranging precision in a multipath environment is further improved.

Description

technical field [0001] The invention belongs to the field of information signal processing, and relates to a pulse ranging method. Background technique [0002] The pulse ranging method is a method of measuring distance by using the time difference between the transmitted pulse and the received signal. Because the method is simple in theory and easy to implement, it is widely used in active sonar systems. In the underwater acoustic pulse ranging system, the timing accuracy determines the ranging accuracy, and how to improve the timing accuracy is one of the key issues in the pulse ranging method. [0003] There is a system delay in the ranging system, and the method of multiple calibration and measurement system delay can effectively reduce the time measurement error caused by the system delay; the underwater acoustic receiver has a certain bandwidth so that some side frequencies cannot pass through, and the integrity of the received signal spectrum If the sensitivity is a...

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Problems solved by technology

[0003] There is a system delay in the ranging system, and the method of multiple calibration and measurement system delay can effectively reduce the time measurement error caused by the system delay; the underwater acoustic receiver has a certain bandwidth so that some side frequencies cannot pass through, and the integrity of the received signal spectrum If the sensitivity is affected, the output waveform of the receiver will produce a certain distortion. In the time domain, it is manifested that the ups and downs of the front and rear edges of the pulse are no longer steep. The received signal is reconstructed by the cubic spline interpolation method, and the peak value of each carrier cycle is accurately calculated. After smoothing the signal envelope, the time delay is estimated by solving the maximum value of the slope to improve the timing accuracy; in a complex underwater acoustic environment, the multipath effect caused by interface reflection or scatterer scattering will produce strong Reverberation makes the ranging system unable to accurately determine the real moment of arrival of the reflected signal, which in turn affects the timing accuracy of the system

There are two commonly used processing methods for this kind of reverberation caused by multipath effects, one is to pre-whiten the reverberation according to the statistical characteristics of the reverberation, and the other is based on the difference between the target reflection signal and the reverberation correlation , using the subspace decomposition theory to separate the reflection signal and the reverberation signal from the echo signal. These two types of methods have the ability to improve the signal-to-mixture ratio, but these algorithms are all based on the reverberation caused by the multipath effect. Inhibition, complex algorithm and poor real-time performance

In addition, since all reverberation cannot be suppressed, interference artifacts still exist, which is not conducive to accurate estimation of arrival time

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