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根据移动通信的特点和80系列技术指标的规定,小频偏的通信装备多采用调相制度。用调相方式传输话音时,其频谱在整个音频频率范围内分布,而信号谱线强度是满足贝塞尔函数展开式的,因此如何抑制调相边带,从而避免邻道干扰是个严重问题。从调相波的调制指数 B=KA_0看,不论调制频率怎样变化β值都是一样的,因此为了抑制调制边带,对于调相波则要有相当复杂的过程和相应的电路来保证。这种过程的简称叫 IDC过程。
According to the characteristics of mobile communications and 80 series of technical indicators, small frequency offset communication equipment and more use of phase modulation system. When the speech is transmitted in the phase modulation mode, its spectrum is distributed over the entire audio frequency range, and the intensity of the signal spectrum satisfies the expansion of the Bessel function. Therefore, how to suppress the phase modulation sideband and avoid adjacent channel interference is a serious problem. From modulation index B = KA_0 of phase modulation wave, no matter how the modulation frequency changes, the value of β is the same. Therefore, in order to suppress the modulation sideband, a very complicated process and a corresponding circuit are required for the phase modulation wave. The abbreviation of this process is called IDC process.