The Design of Clocked-Comparator-Based Time-Interval Measurement Circuit for Pulse ToF Measurement

A clocked-comparator-based time-interval measurement approach is proposed for the measurement of the time-of-flight (ToF) of wave pulses in a threshold-crossing-detection-based pulse ToF range-finding application. As compared to the conventional TDC-based pulse ToF measurement approach, the proposed approach does not require the use of extra channels in the case where multiple echoes can be expected for every wave pulse launched. As compared to the conventional (flash) analog-to-digital converter-based pulse ToF measurement approach, the proposed approach allows for a simpler backend digital processing and does not require the comparators used in the measurement to be skew-less. Meanwhile, the approach leverages on the strength of a clocked comparator circuit, which can be designed with a very wide sampling bandwidth. A clocked-comparator-based time-interval measurement circuit with a ~7-GHz bandwidth was assembled using low cost commercial-of-the-shelf components. The measurements done using the measurement circuit agree to within 10 ps with the same measurements done using a 13-GHz, 40-GSa/s oscilloscope and are precise to within ±15 ps in terms of their 2σ range.