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在频谱扩展任意选取通信系统中,通信线路的建立必须再生载波和取得伪随机码的同步。但在这种系统中,由于所有信道公用同一频带,在发射端就不能插入导频信号,因而难以再生载波,造成同步建立的困难。为解决这个问题,本文提出一种工作原理与锁相环类似的载波再生电路,叙述其分析结果。这种载波再生电路应用一个频偏识别器,即使当信号被调制,载频偏移其额定值时,频偏识别器产生一个与频偏量成正比的电压。当各发射台频率变化独立且很大时,这种方法就不能使用,为此,利用非线性电路和伪随机码的特性,提出不用再生载波而取得伪随机码同步的电路,并叙述这个方法的分析结果。最后简单地谈一下载波搜索和伪随机码相位搜索同时进行的并列跟踪系统。
In the spectrum extension of any selected communication system, the establishment of communication lines must regenerate the carrier and obtain the synchronization of the pseudo-random code. However, in this system, since all the channels share the same frequency band, pilot signals can not be inserted at the transmitting end, making it difficult to regenerate the carrier, resulting in the difficulty of establishing synchronization. In order to solve this problem, this paper proposes a carrier regeneration circuit whose operating principle is similar to that of a phase-locked loop, and describes the analysis results. This carrier regeneration circuit employs a frequency offset discriminator that generates a voltage proportional to the frequency offset even when the signal is modulated and the carrier frequency shifts its nominal value. This method can not be used when the frequency of each transmitting station is independent and large. Therefore, by using the characteristics of nonlinear circuits and pseudorandom codes, this paper proposes a circuit to obtain pseudo-random code without regenerating carrier and describes this method Analysis of the results. Finally, simply talk about carrier search and pseudo-random code phase search at the same time parallel tracking system.