Jitter measurement system and method

Abstract

A jitter measurement system measures timing variations or “jitter” in a periodic signal waveform as provided, for example, by a phase-locked loop (PLL). In one implementation, the jitter measurement system includes a period gate generator that generates a gate signal with the instantaneous period of output signal waveform F,generated by the PLL. The gate signal includes a leading edge and a trailing edge and is delivered to a pair of triggered oscillators that provide respective oscillator output signals with substantially matched frequencies. The oscillators are triggered at the respective leading and trailing edges of the gate signal. The oscillator output signals are delivered to respective oscillation counters and to a coincidence detector. The oscillation counters count the periods of the respective oscillator output signals from when they are triggered until the coincidence detector detects coincidence between the signals (e.g., coincidence between the trailing edges of the signals). A period measurement of the output signal waveform F,is determined from the counts obtained by the oscillation counters. Multiple such period measurements are obtained to provide information representing jitter in the output signal waveform F,.