Constant-rate clock recovery and jitter measurement on deep memory waveforms using dataflow

Abstract

The measurement of jitter is key when verifying the design or performing manufacturing test of ever more complex digital communications circuitry or equipment. As the requirements for bit error rates (BER) become more stringent and data volumes increase, it becomes increasingly important and interesting to measure timing jitter in long, or even temporally unbounded, waveforms. Previous methods for doing constant rate clock recovery and jitter measurement required storing and computing on all samples of the waveform at once. As the waveform grows, and especially if the waveform is unbounded, this storing it in its entirety becomes impractical. We demonstrate the transformation of the previous method to a dataflow method where the entire waveform need never be stored. The new method has been tested on actual measured data. Through its incorporation of dataflow principles, the new method is suitable for efficient mapping to a variety of platforms, including multicore and field programmable gate array platforms for high performance signal processing. Intermediate measurement results converge toward those obtained in the original method. The final measurement result, the jitter standard deviation, agrees with the original method to within well under one percent. Thus, a small amount of additional measurement error is added in order to remove the restriction that the entire waveform fit into memory.