调制无线电信号的分形特征研究

Study on fractal features of modulated radio signal

调制方式的不同以及信号受到功率放大器的非线性变换决定了调制无线电信号的形状存在着差异,提取这些差异特征是信号识别的基础.基于分形理论提取信号特征是一种新的方法,本文模拟了在不同信噪比条件下,通过计算调制无线电信号的方差分形维以及Mandelbrot奇异分形维谱,将信号的调制特征以及非线性变换特征投射到分形特征空间.数值仿真结果表明,不同调制方式、非线性变换对应了分形特征空间中的不同位置.这些结果表明分形理论能够有效提取无线电信号的调制特征以及功率放大器的特征,对信号的调制方式以及个体特征识别具有一定的工程应用价值.

The shape of radio signals determined by modulation system and that produced by the nonlinear transform are different in kind,which is the basis for discriminating them.Feature extraction based on fractal theory is a new method.In this paper,the features of modulation and nonlinear transform are projected to fractal feature space by computing the variance fractal dimension and the Mandelbrot singularity spectra dimensions.The numerical result show that differences in fractal features do exist between different modulated signals and the nonlinear transformed signals.The results show that the feature of these signals can be extracted based on fractal theory,which has engineering value for the identification of modulated radio signals.