软扩频Multi-h CPM信号设计方法及其性能

Signal design and performance of tamed spread spectrum based Multi-h CPM

为解决传统多调制指数连续相位调制(Multi-h CPM)实现复杂度高和调制指数同步困难的问题,提出一种软扩频Multi-h CPM信号设计方法。利用单调制指数软扩频获得Multi-h CPM类似的相位轨迹和性能增益,伪码捕获的同时实现调制指数同步;推导了软扩频Multi-h CPM欧氏距离表达式,搜索获得了h=5/7时的最小欧氏距离,与直接序列扩频单调制指数CPM(DSSS Single-h CPM)信号相比,至少可获得0.5 dB的欧氏距离增益。基于极大似然序列检测(MLSD)的同步解扩解调算法,仿真了h=5/7的软扩频Multi-h CPM误码性能,与DSSS Single-h CPM信号相比,在BER=10–5时,可获得1.5 dB性能增益,且性能优于美军WGS系统和ARTM Tier II系统采用的Multi-h CPM信号。

To overcome difficulties of high complexity and modulation index estimation in conventional Multi-h Continuous Phase Modulation（Multi-h CPM）, a new Multi-h CPM signals format based on tamed spread spectrum technique is proposed, which can obtain similar phase state trellis structure and performance gain as conventional Multi-h CPM signal. Moreover, the modulation index synchronization can be completed while the pseudo random spreading sequence is synchronized. The paper provides the Euclidean distance expression and searches the minimum distance of h=5/7. It shows that the proposed signal format can obtain 0.5 dB gain in terms of minimum Euclidean distance compared with the conventional Direct Sequence Spread Spectrum（DSSS） Single-h CPM. The synchronous de-spreading and demodulation algorithm based on Maximum Likelihood Sequence Detection（MLSD） can be used for optimum receiver. Numerical results show that tamed spread spectrum Multi-h CPM signal format can obtain a performance gain of 1.5 dB with a Bit Error Rate（BER） of 10-5 compared to DSSS Single-h CPM. Moreover, it outperforms WGS and ARTM Tier2 system.