Phase measurement apparatus and method

Abstract

A phase measurement apparatus and method for measuring electrical signal jitter and wander operates in real time and digitally controls bandwidths over which the measurements are performed. The apparatus includes a digital phase-lock loop (PLL) for generating phase difference signal data having first and second frequency components above and below the loop bandwidth of the phase locked loop. An analog-to-digital converter digitizes the analog phase difference signal from the phase detector. A digital signal processor (DSP) receives the digital data and performs a loop filter function for generating frequency update values to the DDS for phase locking the PLL to an incoming signal. The DSP performs an integration function on the loop filter function output to generate the second frequency components. The first and second frequency components are combined in a summing circuit and filtered in digitally programmable low and high pass filters for establishing measurement bands for measuring the phase difference. A measurement processor measures peak-to-peak minimum and maximum values and generates RMS values of the phase difference signal over a selected time interval and generating an output in unit intervals for jitter and time for wander. The DSP further includes low and high pass filter functions and an accumulator for summing filtered second frequency components to generate wander data. The DSP processes the frequency update values to generate frequency drift data.