二阶锁相环的EBPSK信号解调分析
doi: 10.3724/SP.J.1146.2007.01325
EBPSK Demodulation Analysis Based on Second-order Phase Locked Loop
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摘要: 高效的调制和解调技术对数据传输具有重要的意义。该文在已有的EBPSK传输系统基础上，详细讨论了EBPSK信号采用二阶锁相环解调时鉴相器的输出信号结构。首先通过建立锁相环的线性化模型，对比分析了不同阻尼系数的相位阶跃误差响应和矩形相位误差响应，推导了理想状态下鉴相器输出的波形表达式。其次在包含窄带高斯噪声的条件下研究了EBPSK信号解调的最佳积分限取值，给出了相应的仿真结果。分析表明，在一定的信噪比条件下，只要锁相环能由捕获状态恢复到跟踪状态，就能保证EBPSK信号的有效解调。Abstract: High efficiency modulation and demodulation techniques are significant for data transmission. Based on present EBPSK transmission system, a kind of demodulation method that employs a second-order PLL with its PD output structure is discussed in the paper. Firstly, PLL linear model is established in order for the comparative analysis between phase step error response and phase rectangular-pulse error response under different damping ratio. The ideal PD waveform expression is figured out. And then in case of narrow bandwidth Gauss noise condition, an optimal integral length for EBPSK demodulation is explored, with its corresponding simulation results. Finally it is demonstrated by simulations that, once PLL is capable of retrieving tracking state from capturing state in some SNR condition, effective EBPSK demodulation is available.
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