科技英语课程
论文（报告、案例分析）
院系物理与电子工程学院
专业电子信息工程
班级电工211班
学生姓名刘脐中
学号 2012128041
任课教师罗倩倩
2014年 12 月 9日
Howling suppression system report
Liu Qizhong
Electronic and Information Engineering
Hubei University of Arts and Science
1454814125@
Abstract：The class D power amplifier based on TPA3112D1 TI, to collect speech signal pre omnidirectional microphone,
Through the signal extraction, filter, power amplifier and other processing,through a 8 ohm 5W horn sound output, and through the whistle frequency detection circuit feedback, by higher order program control wave trapLTC1068-25, complete the howling detection, howling suppression and powercalculation and other functions, the higher system efficiency.
Key words：Class D power amplifier;Detection of squeal frequency;Programmable notch filter
1 Introduction
TI power amplifier chip based on TPA3112D1, audio amplifier design andmake a howling detection and suppression function, complete desktopmicrophone amplifies the audio signal through the power amplification circuit to send the speaker output.To further improve the howling suppression circuit. In the precondition of ensuring no whistling, try to improve audio power.The output power of the amplifier.
2 Materials and Methods
The final selection of the STM32 as the main control chip, the selectionreason: compared with STM32, TI M4 ARM also Coretex architecture based on80M clock, timer, but poor stability, and no built-in DA, difficult to meet the requirements, so the final system using STM32 as the MCU unit.
3 The Improved Method
3.1 Method one
With three tubes, by reasonably setting the static working point, to the electretseries resistance equivalent resistance,
Dynamic voltage by capacitance coupling mode to acquisition the electret microphone at both ends, to achieve a more sensitive collection effect, also a certain degree of noise suppression.
3.2Method two
Using operational amplifier noninverting input capacitance coupling mode,using the high input impedance, to collect speech signal, while suppressing the purpose of dynamic noise.
3.3Discussing about method one
A scheme of low cost, but the pickup effect is not clear, the selection of LM358special audio amplifier chip, can better do front audio amplification, the choice of scheme two.
4 Conclusion
This system to suppress squeal core to notch, with three grade for different values of Q notch filter cascade, real-time tracking of input signal of whistlers,complete suppression, effect is good, the two howling suppression is better,the shortage is that: the system stability is poor, at all levels of the connectionis more complex, especially MCU peripheral connection is not stable, also need to be greatly improved. Consider other occupy part of interrupt, the keyreaction is slow control power, the need to improve.
References
[1] <Analog electronic technology>(Tong Shibai)2006
[2]<Test analysis of transistor circuit design -- amplification circuit technology>(,2)2008
[3] <Analog electronic technology>(Sun Xiaozi )2006
带啸叫检测与抑制的音频功率放大器
刘脐中
（湖北文理学院，物理与电子工程学院）
1454814125@
摘要：本文基于TI的D类功放TPA3112D1，以前置全向麦克风采集语音信号，
通过信号提取，滤波，功率放大等处理，通过8欧姆5W喇叭输出声音，并通过啸叫声频率检测电路反馈，由高阶程控陷波器LTC1068-25，完成啸叫检测、啸叫抑制以及功率计算等功能，系统效率较高。
关键词：D类功放啸叫声频率检测程控陷波器
1引言
基于TI的功率放大器芯片TPA3112D1，设计并制作一个带啸叫检测与抑制功能的音频放大器，完成对台式麦克风音频信号进行放大，通过功率放大电路送喇叭输出。
进一步改进啸叫抑制电路。
在保障无啸叫的前提下，尽量提高音频功率放大器的输出功率。
2材料和方法
最终选用STM32作为主控芯片，选型理由：与STM32相比，TI M4 也是基于ARM coretex构架，时钟高达80M，但是定时器稳定性较差，且无自带DA，难以满足要求，所以本系统最终采用STM32作为MCU单元。
3改进方法
3.1方法一
采用三级管，通过合理设置静态工作点，给驻极体串联阻值相当的电阻，
以电容耦合方式采集驻极体话筒两端的动态电压，达到较为灵敏的采集效果，同时一定程度抑制噪声。
3.2方法二
采用运算放大器同相输入电容耦合方式，利用其高输入阻抗，达到采集语音信号，同时抑制动态噪声的目的。
3.3选择方法
第一种低成本方案，但拾取效果是不明显的，所以选择音频放大器 lm358special 芯片，这样可以更好地做前置音频放大，故选择两方案。
4结论
本系统抑制啸叫核心为陷波，采用三级不同Q值陷波器级联，实时跟踪输入信号的啸叫声，完成抑制，效果较为良好，二次啸叫压制较好，不足之处在于：系统稳定性较差，各级连线较为复杂，尤其MCU的外设连线较不稳定，还需要极大的改善。
考虑其他部分占用中断等，控制功率的按键反应较慢，需要改进。
参考文献
[ 1 ] 《模拟电子技术》（童诗白）高等教育出版社，2006
[ 2 ] 《测试分析晶体管电路设计》——放大电路技术，2008版
[ 3 ] 《模拟电子技术》（孙肖子）西安电子科技大学出版社，2006。