A Time-to-Digital Converter Based on Time-Space Relationship

This paper describes a time-to-digital converter based on time-space relationship to improve the measuring precision of time interval. A tapped transmission line of certain length is used as the delay line, which converts the measured time to length. The delay characteristics and electrical performance of two types of transmission lines, coaxial cable and microstrip, are analyzed, as well as the factors affecting the delay characteristics, such as loss and temperature. The coincidence detection of the delayed start signal and stop signal is so critical that a type of coincidence detection circuit is developed, of which the uncertainty is 14 ps. Buffer is used to enlarge the measurement range. The structure of the time-to-digital converter is also presented, of which the quantization error, integral nonlinearity error and random error is analyzed. An advantage of this kind of time-to-digital converter is easy to be integrated. Based on the CMOS technology, a chip is designed, and a simulation of the chip is performed, which presents 23 ps single-shot precision. As a demonstration of this principle, a prototype using the microstrip on a printed-circuit-board as delay line is realized with 108 ps single-shot precision.