Time Pickoff Method Using Dual-Edge Discrimination to Mitigate Time Walk

Abstract

Precise generation of a timing pulse at the signal is crucial for high-resolution time measurements, accomplished using a time pickoff circuit. The primary challenge in time pickoff circuits is to minimize the dependency of timing pulse generation on signal amplitude, which causes a timing error known as time walk. This study proposes a time pickoff method using dual-edge discrimination, which measures the crossing times of the signal at both its leading and trailing edges and calculates a reference time when the signal reaches its peak amplitude. The proposed time pickoff method was theoretically analyzed, demonstrating that the reference time was independent of variations in the crossing times due to the signal amplitude variations. Furthermore, the timing error caused by the charge sensitivity of the comparator used in the time pickoff circuit was reduced. The proposed time pickoff method was validated through experiments for signals with 2-ns rise and 3-ns fall times and amplitudes ranging from 18 mV to 1.8 V, resulting in a time walk of 145 ps.

Keywords

• Charge sensitivity
• dual-edge discrimination
• time-of-flight
• time pickoff
• time walk