Abstract:

The sine nonlinear chirp keying (SNCK) signal is affected by the phase error and Doppler frequency shift when received by the coherent demodulation method. To solve this problem, by using the segment linear frequency modulation (LFM) signal to approximate it, a fractional Fourier transform (FRFT) incoherent demodulation method is proposed. The performances of FRFT demodulation and coherent demodulation are compared by theoretical analysis and simulation. Under strict synchronization conditions, the SNCK signals demodulation performance using the coherent demodulation is better than the FRFT demodulation, and the length of the signal element has slight effect on the FRFT demodulation performance. However, the FRFT demodulation is not affected by the phase error, and has a high ability to resist the Doppler frequency shift.