The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Measurements >> Phase Noise and Jitter Measurements >> Question for Peaks on the PNoise Result's Curves
https://designers-guide.org/forum/YaBB.pl?num=1129284499

Message started by tumeda on Oct 14^th, 2005, 3:08am

Title: Question for Peaks on the PNoise Result's Curves
Post by tumeda on Oct 14^th, 2005, 3:08am

Hi

I would like to know where these peaks on the curves of PNoise simulation come from ? As the description on the paper "jitter&Noise", after the -20dbc/Hz, the curve should be a flat line.
Hier are the schematic of VCO and PNosie response. If you can not see the pictures, pls use right mouse to show the pictures.
I am very appreciate your help.

Title: Re: Question for Peaks on the PNoise Result's Curv
Post by tumeda on Oct 15^th, 2005, 1:20pm

Pictures are updated!
http://img140.photo.163.com/zoujunjx/17445359/441491786.jpg
http://img140.photo.163.com/zoujunjx/17445359/441519850.jpg

Title: Re: Question for Peaks on the PNoise Result's Curv
Post by Ken Kundert on Oct 15^th, 2005, 5:31pm

Is the oscillation frequency approx 200MHz? If so, the bumps are the harmonics of the oscillation.

-Ken

Title: Re: Question for Peaks on the PNoise Result's Curv
Post by tumeda on Oct 18^th, 2005, 2:29am

Thanks for Ken's guidance!
I have found the frequency at the first bump is the VCO oscillation frequency. The other bumps are not very exact harmonic.
Question: As long as I select the f_c<delt_f<f_vco, these bumps will not influence the jitter calculation, like as the delt_f=10M in this circuit.
Is it right?

Title: Re: Question for Peaks on the PNoise Result's Curv
Post by Ken Kundert on Oct 18^th, 2005, 9:32am

Correct.

The bumps are precisely at the harmonics, they just appear to be a different frequencies because of the frequency points used during the analysis.

-Ken