中文摘要：

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。

英文摘要：

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.