Time interval measuring apparatus and jitter measuring apparatus using the same

Abstract

In order to stably measure an input interval time of a pulse signal with high precision, a time interval measuring apparatus includes a reference signal generator, a phase shifter, first and second A/D converters, an error correction unit, an instantaneous phase calculation unit, and an interval time calculation unit. The phase shifter divides a reference signal of a sine wave having a predetermined frequency from the reference signal generator into a first analog signal and a second analog signal having phases shifted to each other. The first and second A/D converters perform sampling of the first analog signal and the second analog signal from the phase shifter, respectively, at an input timing of a pulse signal to be measured, and output a first and second digital sample values. The error correction unit corrects direct current offset errors generated in, respectively, the first and second digital sample values output from the first and second A/D converters, a phase error with respect to 90°, and an amplitude error. The instantaneous phase calculation unit calculates an instantaneous phase of the reference signal based on the corrected first and second digital sample values. The interval time calculation unit determines an input interval time of the pulse signal based on a variation of instantaneous phases.