ANovel Method for Binary Chirp-Rate Modulation and Demodulation

Chirp-rate modulation (CRM) is a kind of technique of spread spectrum which has the ability of anti-multipath and anti-interception. Meanwhile as a modulation method, CRM can be combined with other spread spectrum methods to compose a hybrid-spread-spectrum scheme and increase the system capability. In this paper, the method for binary CRM based on the fractional Fourier transform is investigated, and a convenient noncoherent demodulation method is presented. The peak of the output of the demodulator is derived. And the effect of Doppler shift is analyzed, which shows the inherent immunity against Doppler shift. Finally, simulation results show that the performance of this proposed method is worse than optimal matched demodulation by about 3 dB, but without needing of rigorous phase synchronization