超外差式晶体管收音机
超外差式晶体管收音机
赵强
（东北电力大学信息工程学院通信工程专业13届学
生，吉林，吉林，132012）
摘要：超外差晶体管收音机一般都是由变频、中频放大、检波、低频放大和功放等几部分组成。自天线接收下来的高频信号，被输入到调谐回路选出后，送到变频级；变频级包括本机振荡和混频器两部分。本机振荡器产生的震荡信号，其频率比输入高频信号高465khz ，这两个信号同时送入混频器进行混频，混频后产生一系列新的频率信号，其中出输入的高频信号及本机振荡信号外，还有频率为两者之和的和频信号以及两者之差的差频信号等。这些信号经过接在混频器输出端的调谐回路选择后。之允许差频信号通过。由于本机振荡信号与输入高频信号的差为465khz ，并且本机振荡器的振荡与输出回路与输入回路的调谐电容器是同轴联调的，不管如何调节，都使差频为465khz 。也就是说，不论接收哪一个电台的信号，经变频器送到中频放大器的信号总是一个固定的频率即465khz 。这个固定的中频信号再经过中频放大器放大到一定程度后，再送入到检波器进行检波，将音频信号选出来；检波输出的音频信号，经过低频放大器和功率放大器 最后推动扬声器发出声音。
关键词：变频 465khz 检波
Abstract : superheterodyne transistor radios are generally
formed by conversion and IF amplifier, composed of detection, low-frequency amplification and amplifier of several parts. Since the high-frequency signal received by the antenna down, is input to the selected tuning circuit, to the conversion stage; conversion stage comprises a two-part local oscillator and a mixer. The oscillation signal generated by a local oscillator, a high-frequency signal having a frequency higher than the input 465khz, these two signals are simultaneously fed to the mixer for mixing, to produce a series of new mixing frequency signal, wherein the input frequency signal and the local oscillation signal, there is the sum of both frequency and the frequency difference between the two signals and difference frequency signals. These signals are connected to the output of the mixer tuned circuit selection. It allows the difference frequency signals. Due to the difference of the local oscillator signal and the input high-frequency signal is 465khz, and the oscillation of the local oscillator and output circuit and input circuit tuning capacitor is coaxial FBI, no matter how to adjust, have made the difference frequency is 465khz. That is, regardless of which station the received signal, the drive signal to the IF amplifier is
always a fixed frequency that is 465khz. This fixed intermediate frequency signal and then through an intermediate frequency amplifier to a certain extent, and then be fed to the detector detecting the audio signal is chosen; audio signal detection output, after low-frequency amplifier and power amplifier, and finally push the speaker sound.
Keywords : frequency 465khz detection
引言：低频有效发射出去需要经过高频信号的调制，利用高频信号作为载波，对信号进行调整，可有多种调制方法。在无线电广播中有调频制和调幅制两种方法。目前调频和调幅式收音机都采用超外差式，它具有灵敏度高、工作稳定 、选择性及失真度小的优点。
一. 系统整体设计：
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二. 系统硬件设计：
1. 变频器
变频级以VT1为中心组成。