基于FRFT滤波的SNCK通信系统接收方法

正弦型非线性切普键控（sine non linear chirp keying，SNCK）作为一种非线性调频方法，其已调信号缺乏有效的滤波技术，针对此问题，提出了一种将SNCK已调信号波形样本近似为分段线性调频信号进行分数阶傅里叶变换的处理方法.推导了采用SNCK调制参数计算相应FRFT变换阶数的公式，并给出了通信系统采用SNCK信号进行传输时，接收端采用FRFT方法进行前置滤波的框图.通过数值仿真分析验证了该方法对SNCK各调制参数的普遍适用性，能有效提高接收信号的信噪比改善因子，降低通信误码率.

Receiving method in SNCK communication system based on FRFT filtering

As a kind of nonlinear frequency modulation method, the sine non linear chirp keying （SNCK） lacks the effective filtering technique for the modulated signals. In order to solve the above mentioned problem, a processing method, where the waveform samples of SNCK modulated signals were approximated into the segment linear frequency modulation （LFM） signals and the fractional Fourier transform （FRFT） was performed, was proposed. The formula for calculating the corresponding FRFT order with the SNCK modulation parameters was derived. When the transmission of communication system was performed with the SNCK signals, the block diagram for the previa filtering through adopting FRFT at the receiving terminal was given. Through the numerical simulation analysis, the universal applicability of the proposed filter method to each modulation parameter for the SNCK signals is verified. Moreover, the proposed method can effectively enhance the improvement factor of signal to noise ratio （SNR） for the received signals, and reduce the bit error rate （BER） for communication.