Analysis Of Characteristic And Experimental Verification Of SNCK Modulated Signals

Due to the high error rate performance under Doppler in single-frequency wave,non-single-frequency wave communications system gradually attracts people's attention.Nonlinear FM signal, as the representatives of the non-single-frequency waves has a better energy aggregation, higher bandwidth efficiency, and better anti-Doppler performance.Therefore, the research on nonlinear FM signal has become a hot topic for modern wireless communication. In this paper, based on SNCK communication system, the characteristics of the modulated signal SNCK are intensively studied. The main contents are as follows:Firstly, based on the non-single-frequency wave signals for the continuous waveform optimization, SNCK waveforms were designed. The SNCK communication system according to SNCK mathematical model was built. Time-bandwidth product (TBP) D as the main parameter in SNCK modulated signal. Depending on the nature of the Bessel function,waveform samples were proved to be orthogonal when D = ?/2.The BER performance in different TBP and SNR were analyzed, when the communication channel is with and without the carrier phase difference and Doppler frequency shift.Secondly, the principles of power spectrum, cyclic spectrum, FrFT and cepstrum were introduced, and the method of converting signal above-mentioned domains. The different D values for the power spectrum of the SNCK modulated signal were analyzed. According to the definition of cyclic spectrum, mathematical formulas of SNCK modulated signal's cyclic spectrum were derived. The characteristic of SNCK modulated signal carrier frequency and symbol rate in cyclic spectrum section was deduced. Due to the FrFT magnitude normalization principle, SNCK modulated signal FrFT for different symbols were derived. It is concluded that FrFT is a suitable non-coherent demodulation method for SNCK communication system. The cepstrum detection was applied to the SNCK modulated signal,and the characteristic of cepstrum was analyzed. Meanwhile, the feature changes with the Doppler frequency shift at the different SNR were analyzed.Finally, FPGA-based hardware platform was bufit. discrete frequency smoothing estimation method was used to estimate SNCK modulated signal's cyclic spectrum. The section at f = 0 was searched by using a sliding Hamming window. The FrFT of the SNCK modulated signal was obtained by using sampling type DFrFT technique and then the signal characteristics after transformation was achieved. The results obtained from the hardware platform and software simulation results were compared to verify the consistency of hardware and software platforms.