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看电视、听广播已成为人们日常生活中不可缺少的一部分。人们根据自己的喜好,选择想看的电视频道或喜欢听的电台广播。那么,接收机是如何从众多的电台信号中挑选出人们想看(或听)的电台信号呢?现以超外差收音机为例来回答这个问题。 通常,一个超外差收音机的框图如图1所示。众多电台信号通过天线进入收音机,选频回路从中选出要收听的电台信号(高频已调信号),送至变频器进行变频,产生一个中
Watching TV and listening to radio has become an indispensable part of people’s daily life. People choose to watch TV channels or listen to radio stations according to their own preferences. So, the receiver is how many radio signals from people want to read (or listen to) the radio signal it? The super-heterodyne radio is now an example to answer this question. In general, a block diagram of a super-heterodyne radio is shown in Figure 1. Many radio signals through the antenna into the radio, select the frequency circuit from which to listen to the radio signal (high frequency modulated signal), sent to the inverter for frequency conversion, resulting in a