毕业设计（论文）
题
目
自动增益控制放大器
学 号 ***号
学生姓名 教学院系 专业班次 指导教师 单 位
***
电气与电子工程系 应用电子技术2012级1202122 ***
职 称
成都工业学院
教授
完成日期 2015 年
5 月 25 日
摘 要
为了克服外界各种因素对接收机输入信号的影响，需要使用自动增益控制技术。自动增益控制（AGC）电路是通信设备，特别是通信接收设备的重要电路之一，其主要作用是使设备的输出电平保持为一定的数值。它能够保证在接收弱信号时，接收机的增益高，而接收强信号时则增益低。使输出信号保持适当的电平，不至于因为输入信号太小而无法正常工作，也不至于因为输入信号太大而使接收机发生饱和或堵塞。
本次设计主要研究应用于音频放大的前级电压放大，放大器可以从MP3或信号源输入音频（100Hz~10kHz）信号，可以带600Ω负载或驱动8Ω喇叭（2~5W）。因此设计的电路需容纳的频带范围应较宽，以至于使语音信号通过。由于语音信号的频带范围为100Hz-10000Hz,所以该电路所应设计的频带范围应在100Hz-10000Hz之间，并且电路应该实现增益的闭环调节，通过此电路可以实现增益的自动调整保持在2V（?0.2），本设计中采用的芯片有VCA822程控放大芯片和MSP430F169单片机来进行控制和显示，通过LCD1602显示输入信号幅度大小及频率高低，可以通过按键来控制输出增益的大小。
关键词：MSP430；自动增益控制；滤波；峰值检波；Ｄ／Ａ
I
Abstract
In order to overcome the impact of external factors on the receiver input signal, use AGC technology. Automatic Gain Control (AGC) circuit is a communication device, in particular is an important circuit communication receiving device, and its main role is to make the device output level to maintain a constant value. It can ensure that when receiving a weak signal, the receiver gain is high, and when receiving a strong signal, the gain is low. The output signal to maintain an appropriate level, not because of the input signal is too small and does not work, that does not mean much since leaving the receiver input signal saturation or blockage occurs.
The design of the main pre-amplification applied to the audio voltage amplification, amplifier input audio (100Hz ~ 10kHz) signal from a mp3 or source, can take 600Ω load or drive 8Ω speaker (2 ~ 5W). Therefore, the frequency range of the circuit design should be required to accommodate wider, so much so that the voice signal. Since the frequency range of the speech signal is 100Hz-10000Hz, so the frequency range of the circuit should be designed to be at 100Hz-10000Hz between, and the circuit should be adjusted to achieve a closed-loop gain, through this circuit can automatically adjust the gain is maintained at 2V (+0.2), the design used in the chip VCA822 programmable amplifier chip and MSP430F169 microcontroller to control and display, through LCD1602 display size and frequency of the input signal amplitude level of the output of the gain can be controlled through the key size.
Key words: MSP430; AGC; filter; peak detection; D/A
II
目 录
摘 要 .................................................................................................................................... I Abstract .................................................................................................................................. II 第1章 绪论 ......................................................................................................................... 1 1.1自动增益控制的原理 ................................................................................................. 1 1.2自动增益控制放大器设计内容 ................................................................................. 2 第2章 方案设计 ................................................................................................................. 3 2.1概述 ............................................................................................................................. 3 2.2系统方案论证与选择 ................................................................................................. 3 2.2.1可控增益电路 ...................................................................................................... 3 2.2.2滤波电路模块论证与选择 .................................................................................. 3 2.2.3峰值检波模块论证与选择 .................................................................................. 4 2.2.4显示模块 .............................................................................................................. 4 2.3系统总体方案设计 ..................................................................................................... 4 2.4 本章小结 .................................................................................................................... 5 第3章 电路设计及参数计算 ............................................................................................. 6 3.1概述 ............................................................................................................................. 6 3.2可控增益电路 ............................................................................................................. 6 3.3功率放大电路 ............................................................................................................. 6 3.4滤波电路 ..................................................................................................................... 7 3.5峰值检波电路 ............................................................................................................. 7 3.6麦克风信号采集电路 ................................................................................................. 8 3.7 LCD1602显示和键盘模块 ........................................................................................ 9 3.8 单片机控制电路 ........................................................................................................ 9 3.9 本章小结 .................................................................................................................. 10 第4章 程序设计 ............................................................................................................... 11 4.1主程序流程图 ........................................................................................................... 11 4.2各模块程序流程图 ................................................................................................... 13 4.2.1键盘程序流程图 ................................................................................................ 13
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