基于TDC的无死区频率测量技术研究

Research on Dead-time Free Frequency Measurement Technology Based on TDC

在精密时频测控领域中,高分辨率、无死区的时间间隔和频率测量非常关键,而时间数字转换器(Time to Digital Converter,TDC)是时间频率测量的常用手段。该文研制了基于ACAM公司生产的时间数字转换芯片TDC-GP21和Altera公司FPGA芯片EP4CE6E22C8N的时间频率测量设备,实现了高分辨率的时间间隔测量,测量分辨率达到13ps。同时采用时间间隔测量模块两两组合的方式实现了无死区频率测量,创新性地采用每组3个TDC芯片,共4组搭建了时间频率测量系统,并对组内3个TDC芯片测量结果采用平均值滤波法,使频率测量稳定度达到1.1 ×10^(-11)@1 s,5.6 × 10^(-15)@10000 s,与商用K+K FXE频率计数器指标相当。本设备具有体积小、无需校准、成本低等优点,能够广泛应用到高精度时间间隔和精密频率测量领域中。

In the fields requiring precise time and frequency measurement and control,high-precision,dead-time free time interval and frequency measurements are highly demanded.TDC(Time to Digital Converter) is commonly adopted in time and frequency measurement.In this paper,a self-developed multi-module timeinterval measurement system is built based on the time digital conversion chip TDC-GP21 from ACAM company and the Cyclone Ⅳ FPGA chip EP4 CE6 E22 C8 N from Altera Company.For each time-interval measurement module,a time-interval measurement resolution as small as 13 ps is achieved.By further duplex operating two such time-interval measurement modules,a dead-time free frequency measurement is realized,the time and frequency measurement system involves three groups,each of which has 3 TDC chips.By averaging the measurement results of three TDC chips in each group,a frequency instability reaches 1.1 × 10^(-11) @ ls and 5.6 × 10^(-15) @ 10000 s.This result shows that this self-developed apparatus approaches the performance of the commercial K+K FXE frequency counter.Due to its advantages of small size,no calibration and low cost,this apparatus can be widely used in applications that require high-precision time interval and precise frequency measurements.