Analysis and Detection of S-Shaped NLFM Signal Based on Instantaneous Frequency

—The characteristics typical S-shaped Nonlinear Frequency Modulation (S-NLFM) signal are analyzed, and a detection method for this type of signal is also proposed. First of all, the instantaneous frequency of the S-NLFM signal based on sinusoid modulation and tangent modulation is obtained by phase unwrapping respectively. Then, two characteristics are obtained from instantaneous frequency. Consequently, a recognition method is proposed based on the two characteristics obtained in the previous step. At last, the detection method for the S-NLFM signal is implemented. Simulation results indicate that the proposed method is robust and the detection rate is more than 90% under an SNR condition of 0 dB or higher regardless of the modulation parameters.