Hi guys,

I plug a 200MHz clock into Agi1ent E-444OA and do phase noise measurement. This machine is a spectrum analyzer and capabable of doing phase noise measurement.

I adjust the integration rande to be from 100Hz to 100MHz in phase noise domain. The integral timing jitter is ~3ps-rms. However, when I plug this clock into a real-time scope, the rms jitter is smaller and close to 1.5ps-rms.

This lead me to wonder which readout is real. I'm looking forward to hearing your thoughtful inputs.  

Regards,
Neo