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锁相环应用于通信机是比较早的,然而却不太普遍。这是因为锁相环的各部分是由分立元件构成的,存在的问题很多。譬如在研制方面需要时间,研制的成本高、使用的元件多、可靠性下降等等;所以到目前为止仍没得到广泛应用。可是最近,通信机向多信道发展,由于成本和形状(特别是在移动无线电台中)的关系必须使用频率合成器。组成频率合成器有用晶体振荡器合成的方法和使用锁相环合成的方法。从成本、调整的难易(在锁相环的各部件是用集成电路组成的情况)方面来看,使用锁相环的方法优点较多。如果在频率合成器中应用锁相环,一个或二个晶体振荡器就可以得到数千个信道。锁相环在通信机方面的应用很多,本文只就以下三个问题作具体的说明:1.频率合成器;2.作解调器用的鉴频器;3.作调制器用的移频键控。
Phase-locked loop used in the communication machine is relatively early, but not so common. This is because the various parts of the PLL are composed of discrete components, there are many problems. For example, it takes time to develop, high cost of development, many components to use, decrease in reliability, and so on; so far it has not been widely used. Recently, however, communicators have evolved to multichannel, and frequency synthesizers have to be used due to the relationship between cost and shape, especially in mobile radios. Synthesis of frequency synthesizer useful crystal oscillator synthesis method and the use of PLL synthesis method. From the cost, the difficulty of adjustment (the components of the phase-locked loop is composed of integrated circuits), the use of phase-locked loop method has many advantages. If you use a PLL in a frequency synthesizer, one or two crystal oscillators can get thousands of channels. Phase-locked loop in the communications machine has many applications, this article only on the following three issues for specific instructions: 1. Frequency synthesizer; 2. For the demodulator with the frequency discriminator; 3. Modulator used for frequency-shift keying .