Question:
Why can't I achieve the data sheet phase noise performance when I use the AD9164 evaluation board with on-board ADF4355 as the clock source?
Resolution:
The phase noise plots in the data sheet are measured with a low jitter, low phase noise signal generator, NOT the ADF4355. The ADF4355 has excellent phase noise performance that is suitable for many applications. It is not, however, the lowest noise signal source available, and thus the performance of the AD9164 will be limited by the ADF4355's jitter performance. A more accurate signal source for the clock, like a low jitter, low phase noise signal generator or an ovenized crystal oscillator, should be used in order to achieve the best phase noise performance possible.
For information on improved phase noise performance and contributors to phase noise, please check this article in Analog Dialogue. http://www.analog.com/en/analog-dialogue/articles/analyzing-and-managing-the-impact-of-supply-noise-and-clock-jitter-on-high-speed-dac-phase-noise.html