中文摘要：

针对浅水多波束近场测深中发射未聚焦和单焦点发射聚焦导致纵向分辨力下降的问题,提出了基于Kasami编码的浅水多波束近场多焦点发射聚焦方法。讨论单焦点聚焦原理,并引入具有优越相关性的Kasami编码信号解决多个焦点信号之间的相互干扰问题,通过公式推导了其发射和接收原理,并通过仿真对发射未聚焦、单焦点聚焦和多焦点聚焦3种情况的目标回波强度进行比较,分析表明多焦点聚焦方法具有更窄的发射波束宽度和更高的积分旁瓣比（ISLR）,采用国产首套浅水宽覆盖多波束测深系统进行了水池实验验证,结果表明本方法有效的提高了浅水多波束近场测深的纵向分辨力。

英文摘要：

To solve the problem of longitudinal resolution loss caused by unfocused transmission and single-focusing transmission in shallow water multi-beam near-field sounding,the method of shallow water multi-beam near-field multi-focus transmission focusing is proposed on the basis of Kasami encoding. The principles of single-focusing focus are discussed,introducing Kasami coded signals that have superior correlation to solve mutual interference problem of multiple focus signals. The transmission and reception processes are derived by formulas. Then a simulation is made to compare target echo intensity among unfocused,single-focal and multi-focal transmissions. Analysis indicates that the multi-focus transmission focusing method possesses narrower transmission beam width and higher integrated sidelobe ratio（ ISLR）. Simulation and tank experimental verification based on the domestic MBES（ multi-beam echo sounder） shows that the method can effectively improve longitudinal resolution of shallow water multi-beam near-field sounding.