Recognition of Radar Signals Modulation Based on Short Time Fourier Transform and Reduced Fractional Fourier Transform ⋆

As the useful time-frequency tool, the Fractional Fourier Transform (FRFT) and the Short Time Fourier Transform (STFT) have a great development of signal recognition. And the Reduced Fractional Fourier Transform (RFRFT) was recently proposed and has been used in the recognition and estimation of chirp signals. A new method based on STFT and RFRFT is presented for radar signals modulation recognition. Compared with the old method, the new method reduces calculation and become more agile. It can provide a higher recognition rate when SNR is larger than 0 db. This method is divided into two steps: firstly, according to the envelope curve of rotation angle α domain of radar signals, by judging if the curve peak corresponding fractional order is 1, we can divided signals into two categories; secondly, we use the curve kurtosis to recognize LFM and NLFM; Then by the STFT spectrum peak number we can recognize BFSK and BPSK.