基于循环谱的隐蔽通信性能分析

研究了基于扩频技术的隐蔽通信波形设计，采用大信号掩盖技术和跳码扩频技术，其中大信号和隐蔽信号分别以直接序列扩频(Direct Sequence Spread Spectrum, DSSS)和随机跳码扩频方式产生。对DSSS信号和随机跳码扩频信号的二阶循环平稳特性进行了理论分析，并通过仿真证明了循环平稳特性可用于隐蔽通信波形循环谱分析。首先，理论分析揭示DSSS信号的循环谱在与数据符号速率和码片速率相关的循环频率上，具有由信号的循环平稳性所产生的一系列特征峰值；然而，在随机跳码直扩信号中，扩频码带来的循环平稳性被破坏，导致其循环谱仅在与码片速率相关的循环频率上存在特征峰值;最后，利用循环平稳特性，结合判决门限进行隐蔽信号检测的仿真和分析。

Performance Analysis of Covert Communication Based on Cyclic Spectrum

In this paper, based on the covert communication waveform of spread spectrum technology,the second-order cyclostationarity properties of direct sequence spread spectrum (DSSS) signal and random code hopping direct spread signal are theoretically analyzed respectively, and the cyclic spectrum simulation proves that these properties that can be used to analyze the cyclic spectrum characteristics of spread spectrum covert communication waveform. Firstly, the theoretical analysis shows that the cyclic spectrum of DSSS signal has a series of peaks generated by the cyclostationarity of the signal at the cyclic frequency related to data symbol rate and chip rate;However, the cyclostationarity caused by the spread spectrum code is disrupted in the random code hopping direct spreading signal, its cyclic spectrum only has the peak value at the cyclic frequency related to chip rate. Finally, the simulation results and analysis of covert signal detection using cyclic spectrum combined with decision threshold are given.