Time Interval Measurement Based On Time-Space Relationship

This paper presents a novel method for measuring time interval. The time-space relationship is used to improve the resolution and single-shot precision.The speed of electromagnetic signal traveling in free space is a natural constant, which is of high value and high stability. Therefore, utilizing the transmission line of certain line as delay line to quantize the time interval features high resolution and high precision. The start signal of time interval is delayed by differential units composed of transmission line, which is connected in series. Then the coincidence detectors are placed at every delay unit to detect the coincidence of the delayed start signal and stop signal. In this way, the time is converted to the length. The point where the delayed start signal gets coincident with stop signal reflects the value of the measured time interval. In this paper, the block diagram of system is described, as well as the system model. The errors in the system are analyzed followed by the methods for their correction. Moreover, the contradiction between high resolution and measurement range is analyzed, and inserted buffers for regenerating signal, active delay line and counter are used to work it out.Based on the time-space relationship, a prototype is realized using microstrips as delay line on the printed-circuit board and edge-triggered master-slaver D flip-flop as coincidence detector. The prototype works on the ECL level. The resolution of the prototype is 250ps.With CMOS technology, a time-to-digital converter is designed, which uses integrated transmission line as delay line and D flip-flop as coincidence detector. In addition, the buffer, delay-locked loop and counter is designed to enlarge the measurement range. A simulation of the chip is performed with the software HSPICE. The resolution of 37ps is obtained.