CCSDS航天测控信号的简化非相干检测算法

Simplified Non-coherent Detection of Aerospace TT&C Signals Recommended by CCSDS

针对航天测控系统中CCSDS推荐的连续相位调制(Continuous phase modulation,CPM)信号载波相位难以恢复的问题,文中提出了一种简化非相干检测算法。首先依据最大似然比准则,推导出信号的最优非相干检测算法,然后将基于Laurent分解的CPM信号的线性模型引入,简化非相干接收机结构。同时考虑到信号相位间的连续性,每次分支度量通过处理多个符号时间的接收信号来提高检测性能。简化的接收机由几个前端滤波器和紧随其后的维特比运算部件构成,文中最后给出了L=4的高斯最小频移键控(Guassian minimum shift keying,GMSK)信号的接收性能,结果表明在误码率同为1×10-4的条件下,观察窗口为8个码元长度时,简化非相干检测比起最优相干检测算法只有1.2 dB的性能损失。

A method for simplified non-coherent detection of continuous phase modulation （CPM） signals recommended by consultative committee for space data systems （CCSDS） in aerospace telemetry, tracking and command （TT＆C） system is proposed due to the difficulty in carried phase recovery. Firstly, an optimal non-coherent metric for CPM is derived from the maximum-likelihood principle. Based on Laurent decomposition, the linear expressions of CPM signals are then applied to reduce the complexity of the non-coherent receiver. In consideration of phase continuity, multi-symbol intervals of received signals are considered in every branch metric to improve the performance of the detection. Constructed with few matched filters in the front-end, the simplified receiver uses the Viterbi algorithm to perform the sequence estimation. Simulation results for the simplified non-coherent detection of guassian mini- mum shift keying （GMSK） signals with L=4 are given in the end. It is shown that when the observa- tion interval is 8 bits long, the simplified detector has only around 1.2 dB SNR to obtain the same BER of 1 × 10^-4as the coherent detector.