二维随机跳频系统性能分析

Performance analysis of a two-dimensional random frequency hopping system

针对传统跳频通信信号检测手段成熟,信号参数特征易被提取的问题,本文提出了一种二维随机跳频系统。区别于传统跳频系统使用的正弦基信号,该系统使用不同调频率的Chirp信号作为基信号,使用离散分数阶傅里叶变换结构实现跳频信号的调制。利用多个伪随机码分别控制分数阶傅里叶变换的变换阶次和载波信号中心频率,实现系统参数的二维随机变化,增加了非合作方对跳频周期、定时偏差等参数进行估计的难度,进而增加对信号进行正确接收解调的难度,提高系统抗截获性能。仿真结果表明:二维随机跳频系统在多径衰落信道下误码率性能良好,且当信道中存在单音干扰及线性调频干扰时,该系统能够实现干扰的更加“平均”,从而有效对抗干扰。当使用时频分析算法分别对二维随机跳频信号及传统跳频信号进行跳频周期估计和定时偏差估计时,二维随机跳频信号的估计误差更大。

This paper proposes a two-dimensional random frequency hopping system to address the problems of mature traditional frequency hopping communication signal detection methods and easily extracted signal parameter characteristics.Different from the sinusoidal base signal used in the traditional frequency hopping system,the system uses chirp signals of different frequency modulations as the base signal and the discrete fractional Fourier transform structure to achieve frequency hopping signal modulation.Multiple pseudo-random codes are used to control the transform order of the fractional Fourier transform and the center frequency of the carrier signal to respectively realize the two-dimensional random change of the system parameters and increase the difficulties in the estimation of the frequency-hopping period,timing deviation,and other parameters of the non-cooperative party.These phenomena then raise the difficulty of receiving and demodulating signals correctly and improve the anti-intercept performance of the system.Simulation results show that the two-dimensional random frequency hopping system has a good bit error rate performance under multipath fading channels.Moreover,the system can achieve an“average”interference in the presence of single-tone and linear frequency modulation interferences in the channel,thereby effectively combating interference.The estimation error of the two-dimensional random frequency hopping signal is large when the time-frequency analysis algorithm is used to estimate the frequency hopping period and the timing deviation of the two-dimensional random frequency and traditional frequency hopping signals.