A high-resolution time interval measurement chip in underground positioning system

This paper presents a time interval measurement method in the underground personnel positioning system. The underground mine orientation system uses a sensor network underground to collect personal position information and adopts TDOA (Time Difference of Arrival) algorithm to acquire distance and position information from time interval data. Time measurement is integrated into the sensor to implement the function of getting time information. Delay line interpolation method is used to realize time interval measurement which can meet the need of high accuracy as well as large ranging scale. On-chip full custom implementation is realized in 0.18μm CMOS process using 128 stages of delay cells. The signal path circuit is designed strictly in balance in order to ensure the pulse signal arrives at each register cell at the same time. The simulation accuracy of single delay cell is 67ps and the actual maximum measurement error is approximately 1ns. The results show that the underground positioning accuracy shall be further improved using delay line interpolation.