数字闭环自动增益控制系统设计与实现  

Design and Implementation of Digital Looped Automatic Gain Control

作　　者：赖小强[1] 李双田[1] 

机构地区：[1]中国科学院声学研究所,北京100190

出　　处：《网络新媒体技术》2013年第3期40-45,共6页Network New Media Technology

摘　　要：提出了一种针对语音信号处理的数字闭环自动增益控制(Automatic Gain Control,AGC)系统的设计,详述了数字闭环自动增益控制原理、电路设计与实现。设计中采用一款适用于语音信号处理的低噪声增益可编程放大器(DS4420),FPGA(EP1C3T100C6)通过I2C总线与其连接实现闭环控制。FPGA实时检测放大器输出,通过实时运算,能够有效控制放大器DS4420的增益,实现自动增益控制。针对自动增益控制算法中的对数等复杂运算,文中采用适合于FPGA的CORDIC算法进行简化运算,把复杂的对数运算简化为只包含移位和加减法的简单运算,不仅极大地降低了运算量,同时还保证了很高的精度。该数字闭环AGC系统具有较高的动态范围(60dB),并且自动增益控制算法简单有效,具有运算量小、控制灵活的特点,在实时系统中能够快速有效地完成自动增益控制的功能。通过实验验证分析,该设计能够根据输入语音信号的大小快速有效地调整放大器增益,有很好的工程实用性。This paper proposes a new design of digital looped automatic gain control system for speech signal processing. And the prin- ciple of digital looped AGC, circuit design and system implementation are illustrated in the paper. A programmable - gain amplifier （DS4420）, which is applicable for speech signal processing, with low output noise is used, and it is connected to a FPGA chip （EP1C3T100C6） through I2C bus to realize looped control. The FPGA detects the output of the amplifier in real -time, and programs the gain of DS4420 effectively through implementing the real - time operations. Algorithm of CORDIC, which is suitable for FPGA, is used to solve the complexity problem of logarithms in AGC blocks. It not only reduces the computation, but also reserves the precision. The AGC system has a wide dynamic range of 60dB. The algorithm of AGC is simple and effective, with small computation, and it can control the gain of DS4420 fast and effectively in the real - time system. Through the experiment, it turns out that the design can adjust the gain of the amplifier fast and effectively according to the speech signal which is suitable for practical application.

关 键 词：自动增益控制.AGC 语音信号处理 CORDIC算法 

分 类 号：TN722[电子电信—电路与系统]