一种改进式TAC的高精度时间间隔测量系统的实现

Implementation of High Precision Time Interval Measurement System Based on An Improved Time-Amplitude Converter

摘要:

设计了一种基于改进式时间-幅度转换器(Time-Amplitude Converter, TAC)的高精度时间间隔测量系统。该系统采用集成运放设计TAC中的电流可控的恒流源,并对TAC内部的积分控制部分加入宽带直流放大电路,来提高时间间隔测量的精确度；采用高精度的模数转换器采样TAC的输出,实现高精度时间间隔测量中的模拟到数字的转换；采用现场可编程逻辑门阵列(Field Programmable Gate Array, FPGA)完成系统软件设计,实现对TAC的控制。通过变换TAC的采样电阻的阻值,使恒流源输出不同的电流对电容进行充电,从而使TAC的输出电压满足高精度模数转换器(Analog-Digital Converter,ADC)采集电压的要求。实验表明,在测量时间范围为1us,800ns,400ns,200ns时,该系统的时间间隔测量的最小时间精度为400皮秒。

Abstract:

The paper designs a high precision time interval measurement system based on an improved time-amplitude converter (TAC). The integrated operational amplifier is used to design a large current controllable constant current source of TAC. The wide-band high-frequency direct-current amplifier is also used in the integral control of the TAC to improve the accuracy of time interval measurement. The analog to digital conversion for high precision time interval measurement is realized by using a high precision Analog-Digital Converter(ADC)to sample the output of the TAC circuit. The system software is realized on a Field Programmable Gate Array (FPGA)-based hardware to control the TAC circuit. The constant-current source can output different current to charge the capacitor by changing the sampling resistor value of TAC to meet the demand of sampling voltage for high precision analog-digital converter. Tests shows that the designed system can achieve 400ps precision of time interval under 1us, 800ns, 400ns and 200ns of measurement time range.