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Measurements >> RF Measurements >> question on signal source phase noise
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Message started by harryhu on Apr 6^th, 2011, 2:04am

Title: question on signal source phase noise
Post by harryhu on Apr 6^th, 2011, 2:04am

Shown in the attached file is the phase noise performance of Agilent E8267D-UNX as descibed in its datasheet. Why there is a flat area between 10k and 100k?

By the way, what is the equipment with the best phase noise?

Title: Re: question on signal source phase noise
Post by rfidea on Apr 6^th, 2011, 10:26am

Hi!

It is noise from different sources filtered by the PLL:s inside the signal generator. Most likly the noise at low frequencies, below 1k, is noise from the internal reference oscillator, probably an oven XO. The noise at high frequenies, above 100k, is from the VCO that is generating the output signal. Inbetween the a PLL is filtering the noise from those two sources in such a way it becomes flat.

This is a simplified explaination. The frequency generation inside a signal generator is much more complicated. It consist of multiple PLL:s to be able to generate an arbitary frequency with fine stepping over a wide frequency range, and do that quickly.

Title: Re: question on signal source phase noise
Post by rfcooltools.com on May 5^th, 2011, 7:06pm

harryhu,

The signal generator you show there looks pretty good!
Any of the signal generators that pair up with phase noise test equipment. For example Agilent 8665A (it is obsolete but phase noise is -140dBc at 20KHz offset).

http://rfcooltools.com