Study on M-COSTAS novel coded multi-modulation continuous active sonar signal

By detecting target with continuous transmitting signals, continuous active sonar possess the advantages of tracing target continuously and higher time gain as compared to pulsed active sonar. An important aspect of continuous active sonar technology is transmitting signal design. Based on M sequence and circular COSTAS sequence, this paper proposed a novel coded multi-modulation signal (M-COSTAS)，which got a nearly ideal ‘thumbtack’ range/velocity output as well as a good Target Revisit Rate by using the cyclicity of circular COSTAS sequence. Compared with LFM-COSTAS of the same time-bandwidth, M-COSTAS gets a lower sidelobe in ranging; compared with M sequence coding signal of the same phase coding width and time width, M-COSTAS get a higher range/velocity resolution. On the other hand, the length of M sequence has closely influence on the ranging performance of M-COSTAS, the longer length of M sequence, the lower sidelobe in ranging and the higher range resolution.