Abstract: In view of underwater acoustic emission source is more. To identify the enemy emission source sonar accurately, combined with the time-frequency domain characteristics of DCT（Discrete Cosine Transform）, time-frequency coefficients embedded watermark identification method is proposed based on DCT. Through the time-frequency coefficients of discrete cosine transform to embed digital watermark, this method considers the channel characteristics to generate watermark, combined with the basic characteristics of two-dimensional DCT matrix to change the embedding position of the watermark and the watermark number for simulation test. The detection performance simulation results show that the proposed method can achieve the best way to achieve the optimal embedding without affecting the signal itself, the performance of the detection accuracy can be improved.

Key words: Discrete Cosine Transform（DCT）, unitary matrix, time-frequency domain, digital watermark

摘要： 针对水下声发射源较多的问题，为能准确鉴别敌我声呐发射源，利用数字水印技术，结合DCT（离散余弦变换）的时频域特征，提出了一种基于DCT的声呐水印方法，通过在离散余弦变换域的时频系数中嵌入数字水印，并且综合考虑信道特性来产生数字水印，结合二维DCT的酉矩阵特性改变水印嵌入位置和水印个数进行仿真分析测试。仿真结果表明所提出的方法在不影响信号本身性能的基础上，能够实现最佳的嵌入方式以达到最优的检测性能，检测精度得到提高。

关键词: 离散余弦变换（DCT）, 酉矩阵, 时频域, 数字水印