1、 1 题题 目目 简易频率特性测试仪简易频率特性测试仪 2 简易频率特性测试仪 摘要：简易频率特性测试仪是以 51 单片机为控制核心的一种测量频率的仪器，具有 较宽的可测试带宽。电路由正交扫频信号源、被测网络、混频器、低通滤波器、ADC 以及液 晶显示部分组成。正交扫频信号源 AD9854 采用 DDS 技术产生高稳定的频率、相位、幅度可 编程调制的正弦和余弦信号。 被测网络是一个 RLC 串联谐振电路， 其前后分别添加电压跟随 器和电阻网络使其与相邻电路电阻匹配。混频器采用性能高，功耗低的 SA602A，将信号源 输出的正余弦信号与经过被测网络出来的处理信号进一步处理，产生高频与低频两种信号
2、。 低通滤波器采用 max274 芯片过滤较高频信号，外接元件少，参数调节方便，也具有良好的 抗干扰性。ADC 选用 AD8317 外置，提高 AD 转换性能。整体电路实现了测量较高频率信号的 频率测量及幅频特性与相频特性的显示。 关键词：DDS 技术、中频正交解调原理、RLC 振荡电路。 Abstract：Simple frequency characteristic tester is a metrical instrument which is operated by 51 single chip computer, It has a wide bandwidth. The circui
3、t is composed of orthogonal frequency sweep signal source, the measured network, mixer, low-pass filter, ADC and liquid crystal display part. Orthogonal frequency sweep signal source AD9854 using DDS technology to produce frequency, phase, amplitude and high stability of the programmable modulation
4、sine and cosine signal. The measured network is a RLC series resonant circuit, a voltage follower and the resistor network to match the adjacent circuit resistance respectively before and after adding the. The mixer uses high performance, low power SA602A, the sine and cosine signal source output an
5、d the processed signal measured network for further processing, to produce high and low frequency signal two. Low pass filter using MAX274 chip filter high frequency signals, less external components, easy to adjust the parameters, and also has good anti-interference performance. ADC use AD8317 exte
6、rnal, enhance AD conversion performance. The whole circuit of the display frequency measurement and the amplitude frequency characteristic measurement of high frequency signal and the phase frequency characteristic. Keywords：DDS technology、Quadrature demodulation, RLC oscillating circuit. 3 目录 摘要-1 第 1 章 设计任务 . 4 11 基本要求. 4 12 发挥部分. 4 第二章 方案论证 . 5 2.1 信号源的选择 . 5 2.2 放大器的选择 . 5 2.3 混频器的选择 . 6 2.4 阻抗匹配 7 2.5 整体电路方案 . 7 第三章 理论分析与计算 . 7
