Clock and trigger jitter. Effects on ultrasonic spectroscopy

Two types of sampling jitter in digitizers are distinguished. Trigger jitter causes the average waveform to be a sum of uniformly sampled, but randomly shifted waveforms. Clock jitter introduces random shifts into each individual sample. The authors make analytic predictions of the biases and standard deviations due to both types of jitter on power and phase spectra, and compare these with numerical simulations and experimentally measured standard deviations from three commercial digitizers. Trigger jitter degrades power spectra less than clock jitter. Clock jitter degrades phase spectra near the edges of the passband more than trigger jitter, but less toward the center. Synchronous transient digitization yields lower standard deviations than free-running digitizers