Research On Active Sonar Signal Identification Algorithm Based On Digital Watermarking

The complex ocean is filled with various underwater acoustic signals, and quite a number of them are artificially produced for the detection of the underwater targets or underwater telecommunication. With the development of underwater acoustic confrontation,the signals highly similar with our own are always emitted by enemies to be interference or decoy. Thus,it is urgent to carry out the new research of active sonar signal identification.In order to solve this problem, a method of using the watermark to identity the received signal is proposed in this paper according to the obtained research results of digital watermarking technology. Specifically, embedding the watermark into the detection signal of active sonar, and then detecting whether the received signal contains the embedded watermark to identity the signal friendly or not.The main accomplishments in this paper are as follows:1. Two kinds of active sonar and acoustic confrontation are introduced in detail, and take them as two examples, the receiving and detecting process of the active sonar are deeply analyzed. The active sonar signal recognition system based on digital watermarking scheme is designed on the basis of the underwater acoustic channel.2. On the basis of the existing methods, an active sonar digital watermark algorithm based on the method of the block DCT transform domain is proposed. The algorithm embeds watermark in the active sonar detection signal by the block DCT transform domain,and detects whether the received echo signal contains the watermark by the normalized correlation algorithm. The signal authentication can be identified and the effectiveness of this method is verified through the experimental results.3. Considering that the method based on block DCT may leads to pulse interference between the adjacent two sub-blocks, a digital watermark method based on the DWT and DCT transform domain is put forward. The effectiveness and advantages of this method are verified through the experimental results.4. The watermark influence of sonar signal detection and resolution is analyzed through the sonar signal detection probability curve with different SWR and the ambiguity function. The results show that the influence can be ignored with high embedding ratio.Finally, the paper summarizes the full text, and points out further research directions.