浅海波导远程信混比预报模型

浅海主动探测时,海底混响是目标回波的主要背景干扰,信混比影响主动声纳的性能.混响和目标回波都属于海洋中的散射问题,利用简正波方法,结合平面波散射函数建立了浅海远程信混比预报模型,实现了不同环境参数下信混比的量化分析.仿真比较了不同信号形式、频率以及不同海底底质下的刚性球信混比曲线,从理论上分析了回波随距离的振荡现象.结果表明：用无指向性的声源探测目标时,信混比较低,探测较为困难;宽带信号照射下目标回波更加平稳;简正波之间的干涉导致回波随距离发生振荡,频率越高,干涉结构越复杂;在硬海底环境中信混比相对较小且目标回波振荡剧烈.

Prediction model of echo-to-reverberation ratio in shallow water waveguide

For active detection in shallow water, seafloor reverberation has great influence on target detection, so echo-to- reverberation ratio determines the performance of active sonar. Both reverberation and target echo are scattering problems in ocean. In the paper, long-distance echo-to-reverberation ratio prediction model in shallow water has been built by associating normal-mode theory with plane-wave scattering function. The advantage of this model is that it enables making quantitative predictions of echo-to-reverberation ratio. The model has been applied to rigid sphere submerged in homogeneous water with various signals, frequencies and seafloor conditions. Results show: it is difficult to detect target by using omnidirectional source because of low echo-to-reverberation ratio; broadband signal makes echo smooth relatively; echo fluctuation phenomenon is found and analyzed theoretically as a result of interference among modes especially at high frequency; echo-to-reverberation ratio is low relatively and fluctuates obviously for hard seafloor.