调制域测频原理及工程实现

本文介绍了调制域这一新概念，着重分析了调制域测频方法，给出了所实现的调制域测频系统框图，展示了调制域测试的关键技术：内插技术和无间隔计数技术，介绍了游标内插法，独立提出了斜波内插法和孪生链。

The Principle of Measuring Frequency in Modulation Domain

Modulation domain is a new conception in electronic technology.In modulation domain,the graphs of frequency,phase or time interval are displayed.The measuring method in modulation domain is derived from electronic counter.This method is different from usual counters for an advanced technique called sample being used in the measurement method.So users can get the frequency values of a signal continuously without dead time.There are two key techniques in modulation domain.One is interpolation.The other is counter chain without dead time.With the interpolation technique,users can decrease the quantizition error of the measurements and raise the accuracy of the measurements.There are two interpolation methods to use in modulation domain.The cursor interpolation is the better.It has developed perfectly and can operate reliably.The other method is slope interpolation,which is derived from capacitance interpolation.It is a new and prospective interpolation method,but need to be developed.In order to get rid of dead time between two frequency measurements, counter chain without dead time is used as a key technique.The author studies two kinds of counter chain,that is twin chain and master servant chain.The principle of twin chain is described in the paper.With the measuring method in modulation domain,users can acquire many parameters that can hardly be measured with usual method.These parameters include:single shot,precision VCO characterization(settling time,overshoot,and post tuning drift);jitters analysis(time deviation,frequency deviation);phase locked loop studies (rise time,ringing,overshoot,and settling time);frequency stability measurements(continuous measurements, direct computation of root Allan variance).The author studies interpolation methods and counter chain.An electronic system to measure frequency in modulation domain is designed and completed.The system operates in practice successfully.The main frequency of the system is as high as 180MHz.The resolution is 86ps.