High-Precision Time Interval Measurement Based on Triggerable Ring Oscillators and All-Phase FFT Algorithm

We present a novel time interval measurement method that utilizes a ring oscillator circuit triggered by the short pulse representing an event to generate a clock signal synchronous with the event, which is used as the sampling clock of ADC to sample a sinusoidal reference signal. The time interval between the two events is mapped to the initial phase difference between the two points on the sinusoidal reference signal. An all-phase FFT algorithm is subsequently performed to accurately determine the time interval between the two events. We have achieved the singleshot time interval measurement precision of 0.9ps rms.