短波环境下跳频信号检测

Detection of Short-Wave Frequency Hopping Signals

短波电磁环境复杂,定频信号、扫频信号、突发信号等大量干扰信号存在,使得跳频信号的检测存在困难,首先利用短时傅里叶变换将信号变换到二维时频平面上,用功率谱对消的方法来清除大部分定频、扫频等信号;其次根据跳频信号不同于定频信号的特性,提出了一种单元平均选小的恒虚警概率准则(CASO-CFAR),将其扩展到二维并应用到时频平面;最后利用形态学图像处理方法中的开和闭运算及中值滤波器对判决后的二值图像进行处理,进一步解决了判决后残留的星点噪声和信号空洞问题。实验表明,该方法能够抑制定频干扰,凸现跳频信号,为跳频信号的分选、解调等后续工作提供了良好的基础。

Short-wave electromagnetic environment is quite complex,including fixed-frequency signals,burst signals,ane etc.In this paper the difficulty in detecting frequency hopping（FH） signal is analyzed.Signals are expressed by short time Fourier transform.Power spectral suppression method is applied to eliminate fixed-frequency signals,burst signals,and etc.Then,1-D CASO-CFAR is taken into account and is extended to 2-D instance according to the difference between frequency hopping signals and long term signals.Finally,open operation,close operation and median filtering of the morphological image processing are applied to the binary image after 2-D CFAR decision,so the rest noises are eliminated and inanition in signals is smoothed.The simulations show that the long term signals can be eliminated while frequency hopping signals being detected,which provides good precondition for the following processing of frequency hopping signals such as classification and demodulation.