连续波声呐中的调频信号设计方法及性能分析

相对传统的短时脉冲波主动声呐而言,连续波主动声呐是一种新型体制的声呐设备,允许在扫描周期内发射高占空比的信号,并且在发射信号的同时进行侦听,由此可以对水下目标实现连续照射,消除距离盲区。由于发射和接收机制的不同,连续波主动声呐对发射信号的波形和处理方法也各有差异,一是要考虑到"直达波"抑制问题,二是要在时间带宽积和对目标的照射时间间隔两者之间进行折中。针对上述两个问题,设计了一种在连续波主动声呐中发射的新型脉冲串信号,该类信号由多个相互正交的广义正弦调频信号串组成,以此在频域上消除回波与拷贝信号的相关性;后置处理中对接收回波提供了三种不同的方案,在时间带宽积和照射时间间隔两者之间择优选择最佳检测效果。计算机仿真结果表明:该类信号波形以及相应的处理方法可以有效地抑制直达波干扰并给出目标的速度-距离信息。

The design and performance of the frequency modulated signal for continuous active sonar

In contrast to the conventional pulsed active sonar, continuous active sonar is another type of sonar device that allows transmitting high duty cycle signals during the scan cycle and listening while transmitting signals, which can achieve continuous irradiation of underwater targets to eliminate the blind zone. Due to the transmission and reception mechanisms different from the pulsed active sonar, the transmission signal waveform and processing methods are also different, where the problems of the "direct wave" suppression and the compromise between TBP (time-bandwidth product) and time interval for target irradiation need taking into account. Aiming at the two problems, this paper designs a new type of pulse train signal. The signal is composed of several sinusoidal frequency modulation signal strings which are orthogonal to each other. In the post processing, three different schemes are provided for the received echo in order to achieve the optimal detection effect. The results of computer simulation show that the signal waveform and the corresponding processing method can effectively suppress the direct wave interference and give the target velocity-distance information.