摘要

随着科技的进步，调幅发射机的应用越来越明显。调幅发射机的主要任务是完成有用的低频信号对高频载波的调制，将其变为在某一中心频率上具有一定带宽、适合通过天线发射的电磁波。

通常，发射机包括三个部分：高频部分，低频部分和电源部分。

高频部分一般包括主振荡器、倍频器、缓冲隔离级、高频电压放大级、高频频功率放大级。主振荡器的作用是产生频率稳定的载波。缓冲级主要是削弱后级对主振器的影响。低频部分包括话筒、低频电压放大级、低频功率放大级。调制是将要传送的信息装载到某一高频振荡信号上去的过程。我们要实现将采集的音频信号放大调幅后播放出去。

关键词：调幅发射机，中心频率，振荡；

Abstract

With the progress of science and technology, more and more obvious application of the am transmitter. The main task is to complete the low frequency modulation transmitter signal useful for high frequency carrier wave modulation, change it into at a center frequency with a certain bandwidth, suitable for electromagnetic waves emitted by the antenna.

Usually, the transmitter consists of three parts: the high frequency, low frequency part and a power supply.

The high frequency part usually includes a master oscillator, frequency multiplier, buffering isolation level, high frequency voltage amplifier, high-frequency power amplifier stage. The master oscillator is the role of carrier generation frequency stability. The buffer stage is the impact of the level of the vibrator weakened. The low frequency part including microphone, low frequency voltage amplifier stage, low frequency power amplifier stage. Modulation is to transfer the information loaded into the process of a high-frequency oscillation signal up. We want to achieve out play the audio signal acquisition amplification modulation.

Keywords: AM transmitter, center frequency, oscillation;

目录

1 绪论... 5

1.1设计的作用和目的. 5

1.2设计要求. 5

2 调幅发射机的主要性能指标... 5

2.1调幅发射机的工作原理. 6

3 小功率调幅发射机的设计... 7

3．1 方案的选择. 7

3．1．1 拟定调幅发射机的工作原理框图. 7

3．1．2 功率分配及电源电压确定. 7

3．1．3 各级晶体管的选择. 7

3．2 电路形式及工作原理. 7

3．2．1 高频振荡器电路和缓冲级. 7

3．2．2音频放大电路. 8

3．2．3 调制电路. 9

3．2．4前置放大电路. 10

3．2．5功率放大电路. 11

4  调幅发射机各级电路的计算与调试... 12

4．1 各级电路的计算. 12

4.1.1载波级. 12

4.1.2音频放大级. 12

4.1.3调幅级. 13

4.1.4前置放大级. 13

4.1.5调制系数与功率. 14

4．2 电路的调试. 14

4．2．1 载波缓冲电路调试. 14

4．2．2 音频放大电路调试. 15

4．2．3调幅电路调试. 15

4．2．5 前置放大电路调试. 17

4．2．6功率放大调试. 17

4．2．7整机调试. 18

5 心得与体会... 19

6 参考文献... 21

7 致  谢... 22