摘要:本文设计了基于锁相放大器的微弱信号检测装置,用来检测在强噪声背景下已知频率的微弱正弦波信号的幅度值。该系统由加法器、纯电阻分压网络、微弱信号检测电路组成。其中加法器和纯电阻分压网络用于生成微小信号。微弱信号检测电路是以PSD(相敏检波器)为核心,将参考信号经过移相器后,接着通过比较器产生方波去驱动开关乘法器CD4053,最后通过低通滤波器输出直流信号检测出微弱信号,将该直流信号送入单片机进行A/D采样,然后液晶显示出来。经最终测试,本系统能较好地完成微小信号的检测。 65149
毕业论文关键词:微弱信号,强噪声,相敏检测
Abstract:The weak signal detection system is based on lock-in amplifier device. It used for detecting known weak sinusoidal signal under strong noise background.. The system consists of adder, pure resistor partial pressure network, weak signal detection circuit ,etc. The adder cooperate and pure resistor partial pressure network produce small signal. The system uses a phase sensitive detector as the core, shifts the phase of the reference signal, and produces square wave through the comparator to drive switch multiplier CD4053. Finally, DC weak signal is outputted through the low pass filter, and transmitted into the controller, The screen displayed the result. It is turned out that the system detect the week signal successfully.
Key Word:weak signal,strong noise, phase sensitive detection
目录
1 绪论 4
1.1 微弱信号检测技术概述 4
1.2 信号检测的方法及微弱信号的特点 4
1.2.1 常规小信号的检测方法 4
1.2.2 微弱信号的检测方法 5
1.2.3 微弱信号的特点 6
1.3 本文的主要工作 6
2 微弱信号检测装置设计方案选择与论证 6
2.1 方案选择与论证 6
2.1.1 系统方案的确定 7
2.1.2 移相网络设计 9
2.2总体方案论述 10
3 基于锁相放大的微弱信号检测装置设计 10
3.1 锁相放大器原理 10
3.2 移相网络 11
3.3 相敏检波器原理分析 11
3.4 硬件电路设计 13
3.4.1加法器 13
3.4.2纯电阻分压网络 13
3.4.3前级放大电路模块 14
3.4.4带通滤波器 14
3.4.5相敏检波器 15
3.5 程序设计 17
4 仿真分析与程序设计 18
4.1 输入信号波形 18
4.2 经过前置放大电路和带通滤波器后输出波形 18
4.3 参考信号输入输出波形 19
4.4 LM311过零比较器输出波形 20
4.5 开关乘法器输出波形 20
5 测试结果