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毕业论文-超外差式收音机设计，共30页，12335字
摘 要
超外差式收音机是指输入信号和本机振荡信号产生一个固定中频信号的过程。如果把收音机收到的广播电台的高频信号，都变换为一个固定的中频载波频率（仅是载波频率发生改变，而其信号包络仍然和原高频信号包络一样），然后再对此固定的中频进行放大，检波，再加上低放级，功放级，就成了超外差式收音机。
本设计使用双3v电源，利用OCL式音频电路，音频前置和前置放大电路采用NPN型三极管，利用三极管检波实现。频率范围在520KHZ-1610KHZ。超外差式收音机凭借体积小，功耗低，可靠性高，性能好以及易于使系统整体实现少调整等优点，得到了迅速的发展和广泛的应用。收音机也因为电路的发展而日渐趋于小型化，这也给其焊接，组装和调试带来了难度。因此须解决在收音机焊接，组装和调试过程中出现的种种问题，并对其进行分析，这会给收音机的维修带来便捷。

关键词：检波；功放级；振荡；OCL；放大；NPN

amplitude modulation superheterodyne radio design, installation, commissioning and molding
ABSTRACT
Superheterodyne radio refers to the process of the input signal and local oscillator signal to produce a fixed intermediate frequency signal.Radio radio station received the high-frequency signals are converted to a fixed IF carrier frequency (only the carrier frequency is changed, the signal envelope remains and the original high-frequency signal envelope does), then thisfixed intermediate frequency amplification, detector, coupled with the low level class, amplifier stage, it becomes a superheterodyne radio.
This design uses a dual 3v power supply, the use of OCL audio circuit, the audio front and preamplifier circuit uses NPN type transistor, the transistor detector to achieve. The frequency range 520KHZ-1610KHZ. The superheterodyne radio relies on the volume to be small, the power loss is low, the reliability is high,the performance good as well as easy to cause the system complete machine to realize the few adjustments and not to adjust and so on merits,obtained the rapid development and the widespread application.The radio also day after day tends the miniaturization because of circuit development, this also gave its welding, the assembly and the debugging has brought the difficulty,Must therefore solve all sorts of problems which in radio’s welding, the assembly and the debugging process appears, and carries on the analysis to it, this will give radio’s service to bring conveniently.
Key Words:Detector；amplifier stage；oscillation；OCL；amplification；NPN

目 录
摘 要 III
ABSTRACT IV
前 言
1.课题背景 1
2.超外差收音机的优势 1
1.超外差式收音机原理
1.1超外差式收音机原理图 3
1.2输入回路 3
1.3变频电路 4
1.4中放级 6
1.5检波级 7
1.6自动增益控制（简称AGC） 8
1.7音频前置级 9
1.8OCL功率放大电路 10
2元器件参数与选择
元件清单 13
3 PCB板的制作
1.制作步骤 14
2.元器件封装的制作 14
4焊接与调试
4.1焊接步骤和注意事项 16
4.2调试方法及过程 17
4.2.1音频部分调试 17
4.2.2接收部分调试 19
5总体电路原理相关说明与电路图
1.原理图 22
2.PCB图 23
总 结 24
致 谢 25
参考文献 26