Research On Passive Sonar Pulse Detection

Passive sonar is different from active sonar, which uses the pulse signal to detect the target. The features are long distance, and can not easily be found by the enemy, the main task is to detect the operating parameters, measure the line spectrum and track the target. For the above, high-precision time delay measurement is the key. The time delay measurement accuracy is the main factor to restrict the distance measurement accuracy.This paper is based on a small platform, called AUV (Autonomous Underwater Vehicle) and on the basis of the use of three symmetric arrays. This paper discusses the working principles to find directions, the measurement of the position based on beamforming, the adaptive line spectrum enhancing, adaptive time-delay estimation, as well as the frequency of measurement.According to the structure of the paper, chapter2 discusses the direction finding theory of the passive sonar and beamforming based on the mathematical models of the three symmetric arrays. We discuss the error analysis from the principles, and the performance indicators, phase-shift beamforming as well as time-delay beamforming.In the third chapter, we introduce the adaptive time-delay estimation and adaptive line spectrum enhancement. In the first section, we first introduce the principle of the adaptive technology, and then describe least mean square (LMS) algorithm in detail. Time delay estimation is the key technology to passive sonar, high-precision time delay estimation is the focus of this paper. This paper presents the application of LMS adaptive algorithm for time-delay estimate, and improves the traditional LMS algorithm. In Section II, we deduce the formula of the adaptive line spectral enhancement from the principle line spectrum characteristics Determination of the target is another important parameter measurement of passive sonar. Adaptive line spectrum enhancement is the modern typical and representative theory. It uses the principle of the adaptive and contrasts the input signal and the hope signal, so adjusts the output signal-to-noise ratio in order to achieve noise suppression, the line spectrum enhancement.Parameters measurement of Passive sonar is a major task; we select a representative of the pulse frequency measurement of the active sonar among many parameters. There are many corresponding methods; we here introduce a more practical zero-crossing detection and phase difference detection. And two methods are compared.On the basis of above theories in this paper, MATLAB simulation and analysis of the error are made and the improved methods are proposed.