为了使读者对机顶盒的电路结构有进一步的了解,下面分别具体介绍机顶盒各组成部分的作用与工作原理。1.调谐解调器有线电视数字机顶盒调谐解调器的作用与数字卫星电视接收机的调谐解调器的作用是一样的,调谐器将所接收的RF信号变换成固定的中频信号,经A/D转换,送入解调器解调为传输流数字信号。它们的不同之处是:前者调谐器所接收的RF信号频率较低(48～860MHz),频带较窄(约812 MHz),中频频率为36 MHz,并采 In order to make readers have a better understanding of the circuit structure of the set-top box, the following specifically introduces the functions and working principles of each component of the set-top box. 1. Tuner demodulator Cable set top box tuner demodulator and digital satellite TV receiver tuner role is the same, the tuner will receive the RF signal into a fixed IF signal, the A / D conversion, into the demodulator demodulator for the transport stream digital signal. Their difference is: The former tuner receives the RF signal frequency lower (48 ~ 860MHz), the band is narrower (about 812MHz), IF frequency is 36MHz, and mining