Nonlinear feature extraction of power amplifiers in multipath

Fine feature extraction is the basement of specific emitter identification, but existing researches rarely take the channel environment into consideration. To improve the practicability of the technology under the realistic channel, this paper researches on the method extracting of the fine feature under a simple multipath channel, which estimates the impulse of channel response by small-amplitude symbols, extracts the nonlinearity of power amplifier (PA) by bigger-amplitude symbols and reduces the effects of noise by iteration. That is to say, the method is applicable just for signals with different symbol amplitudes. For simulation, we extracted feature vectors using a 16-QAM signal and the support vector machine was used in training and classifying. Experience shows that the method performs well for identifying same-model emitters in multipath channel especially at a higher SNR.