CPM编码调制发展前景

连续相位调制（CPM）技术是一类恒包络的数字调制技术，CPM信号的恒包络这一特性使它们对于非线性信道和衰落信道具有很强的抵抗性．特别适用于卫星通信和移动无线通信信道。与PSK调制方式相比，CPM调制系统不仅能够提供较高的频谱效率，而且具有一定的编码增益，这是因为接收器可以利用相位成型滤波器引入的记忆特性。CPM调制系统可以分解为一个连续相位编码器（CPE）和一个无记忆调制器（MM）的级联，因此出现了多种卷积码与CPM结合的调制方案，例如串行级联连续相位调制、基于环的串行级联连续相位调制、实用的连续相位调制、卷积编码器与扩展信道编码器的串行级联，等等。其中，基于环的串行级联连续相位调制具有很好的性能，在交织增益、自由距离、误码平层和收敛门限可能成为未来连续相位编码调制系统的发展方向。

The Prospect of Coded CPM Schemes

Continuous Phase Modulation （CPM） schemes belong to a class of constant-envelope digital modulation schemes,the constant-envelope nature of the CPM signals makes them robust for the nonlinear and fading channels, and very useful for the satellite and the mobile radio channels.Comparing to PSK modulation,CPM modulation can not only provide spectral economy,but also exhibit a ＂coding gain＂,because the decoder can exploit the memory intro- duced by the phase-shaping filters.CPM can be decomposed into a Continuous Phase Encoder （CPE） followed by a Memoryless Modulator （MM）,so many modulation schemes of combination of convolutionat encoder and CPM modu- lator have arised,such as SC-CPM,SC-CPM with Convolutional Codes over Rings,P-CPM and Concatenation of convolutional endocder and extended CE,etc.Among them, SC-CPM with Ring CCs schemes can offer good perfor- mance,if the interleaver gain,free distance,error floors and convergence thresholds can be investigated in depth,it maybe the development direction of the coded CPM shemes.