With increasing data rates, jitter analysis of reference clock signals becomes more and more important. In the Gb/s range, even small jitter has a significant influence on system performance. Jitter analysis can be performed both in the time domain and the frequency domain, each with its own benefits. This technical paper shows how to characterize RMS jitter by characterizing phase noise using a signal source analyzer, and how to easily separate random and discrete jitter components, while measuring all parameters of interest. Key topics include jitter analysis in the time domain and jitter analysis in the frequency domain.