FAQs from Rohde & Schwarz

RMS jitter from Phase Noise measurement


What's the difference between the integrated measurement with and without the spurs 'hidden' on FSWP, is it supposed to give random-jitter and total jitter directly, respectively and how do I get the total RMS jitter from the instrument directly?


The RMS jitter can be calculated from the phase noise measurement of your spectrum analyzer. When the phase noise measurement result is present the RMS jitter value is equivalent to the area below the graph which can be retrieved by integrating over the given frequency range. That leads to the residual phase modulation.

RMS jitter from Phase Noise measurement - screen 1

By considering the input frequency one receives the value for the RMS jitter in seconds.

RMS jitter from Phase Noise measurement - screen 2

The RMS jitter can be split up into the random jitter and the discrete jitter. In the frequency domain these two parts can be separated from each other. Where the random jitter refers to the noise floor of the phase noise measurement and the discrete jitter to spurs in the spectrum. The relation between the RMS, random and discrete jitter is given as:

RMS jitter from Phase Noise measurement - screen 3

The FSWP is able to display the phase noise measurement without the discrete spurs by using spurious suppression and can therefore calculate the random and the discrete jitter values.

The values can be retrieved from the Spurious Table

RMS jitter from Phase Noise measurement - screen 4

As seen in the screenshot the random jitter in the Spurious Table is equal to the Integrated Measurement jitter in trace 1 which has active spurious suppression. And the integrated measurement will show RMS jitter as long as a trace with spurious is selected(trace 2).