Identification of radio signal pulse modulation characteristics

In the electronic reconnaissance, the identification of radio signal pulse modulation characteristics has vital significance. Firstly, this paper adopts short time fourier transform (STFT) method to analyse the pulse modulation feature of four typical radio reconnaissance signals: linear FM signal (LFM), Tangent FM signal, binary phase coded signal (BPSK), four-phase encoded signal (QPSK). By comparing the time-frenquency curves, the FM signals and the phase modulation signals could be identified. Secondly, wigner-hough transform is used to identify LFM signal and Tangent FM signal according to their different pulse modulation characteristics. Lastly, the identification of BPSK signal and QPSK signal is achieved by extracting the N-th instantaneous frequencies difference. The experimental results show that time-frequency analysis methods that were used in the identification of signal modulation characteristics is feasible and have better noise immunity.