高频石英晶体测试系统信号源设计

Design of the Signal Source Used in High Frequency Crystal Measurement System

介绍了一种高频石英晶体测试系统中信号源的设计,整个设计以直接数字频率合成技术为核心,以高稳定度恒温晶振为时基,使用CPLD和ARM实现信号源的控制。该信号源具有四路输出、输出频率范围宽、频率转换速度快、频率分辨率高的优点,并且可以编程设定输出通道间的相位差,从信号源角度出发为高频条件下石英晶体参数测量提供了一种新的误差补偿方法,提高了石英晶体测量的精度。实验结果表明:信号源输出频率精度高于±0.1ppm,采用该信号源的石英晶体测试系统串联谐振频率测试精度在1～200MHz频率范围内达到±2ppm。

This paper introduces a design method of the signal source used in high frequency crystal measurement system. The signal source is based on DDS （ Direct Digital Frequency Synthesis） technology, uses OCXO （Oven Controlled Crystal Oscillator） as the time base and is controlled by CPLD （Complex Programmable Logic Device） and ARM. This signal source has four output channels, a wide output frequency range, high frequency resolution and quick frequency changing capability. Furthermore, the phase between output channels can be controlled by program. It provides a new error compensation method for high frequency crystal measurement and improves the precision of the measurement. Experiment results indicate that the accuracy of the signal source output frequency is better than 0. lppm and the measurement accuracy of series resonant frequency of the quartz crystal measurement system using the signal source is 2ppm, with the measurement range from 1MHz to 200MHz.