RNA: Advanced phase tracking method for digital waveform reconstruction

Abstract

This paper describes how to measure an eye diagram by using ATE (Automated Test Equipment) digital channel and to do a correlation with an oscilloscope for over-Giga-bps class high speed digital interfaces. The novel method named RNA (Recovering aNAlysis) is a post processing method to perform “phase tracking” in the eye diagram measurement on an ATE which does not have a CDR (Clock Data Recovery) hardware integrated. The RNA is an enhancement of the method named DNA (Data aNAlysis) that constructs an eye diagram by coherent waveform reconstruction with utilizing an ATE digital channel. The DNA is an elegant method to reconstruct digital signal waveform and its eye diagram; however it is not immune to slow jitter or wander of signal. In recent high speed digital interfaces, jitter tolerance is very critical so that the DNA is insufficient for coping with test devices containing slow jitter. The RNA is an enhanced DNA by implementing software quasi-CDR described in this paper. It significantly expands the application coverage. The eye diagram processed by this method is improved and good for parametric measurement such as rise time/fall time tests. Especially, it allows to do an easy correlation to the eye measured by an oscilloscope. Therefore the transition from bench systems to ATE for production test becomes smooth and efficient.