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由于数字通信的快速发展,频带趋于拥挤。近年来提出了许多带宽和功率有效利用的数字调制技术。如最小频移键控(MSK),连续相频移键控(CPFSK),多重h码(MHPM),连续相调制(CPM)等等。MSK信号和CPFSK信号都可看作特殊的CPM信号。由于CPM信号在调制过程中隐含着相位编码,对它的最佳检测是最大似然检测。这可以用维特比(Viterbi)算法实现,称为维特比检测器。这种最佳检测的先决条件是发送端和接收端之间载波相位和符号时间的完全同步。本文从最大似然原理出发推导了CPM信号判决-导引载波恢复环路的结构,分析了维特比检测器对载波恢复的影响。特别是提出了维特比检测器限制相位误差能力这一重要性质。由于这一性质。相位误差过程是一个更新(renewal)过程。本文最后用福克-普朗克(Fokker-Plank)方程和更新过程理论分析了这种载波环路的性能。
Due to the rapid development of digital communications, the frequency band tends to be crowded. In recent years, many bandwidth and power efficient digital modulation techniques have been proposed. Such as MSK, CPFSK, MHPM, CPM and so on. MSK signal and CPFSK signal can be regarded as special CPM signal. Because the CPM signal implies phase coding in the modulation process, the best detection for it is the maximum likelihood detection. This can be done using the Viterbi algorithm, called a Viterbi detector. A prerequisite for this best detection is the complete synchronization of the carrier phase and symbol time between the transmitter and receiver. Based on the principle of maximum likelihood, this paper deduces the structure of CPM decision-pilot carrier recovery loop and analyzes the effect of Viterbi detector on carrier recovery. In particular, the important property of limiting the phase error of the Viterbi detector is proposed. Due to this nature. The phase error process is a renewal process. Finally, the performance of this kind of carrier loop is analyzed by the Fokker-Plank equation and the updated process theory.