The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Simulators >> RF Simulators >> VCO pushing and pulling simulation
https://designers-guide.org/forum/YaBB.pl?num=1151438219

Message started by zzphht on Jun 27^th, 2006, 12:56pm

Title: VCO pushing and pulling simulation
Post by zzphht on Jun 27^th, 2006, 12:56pm

I have an 1.8G VCO. I will inject a sinesoid inteference signal which is very close to 1.8G, say 1.8001G, into the oscillator. Ideally, two spurs at 1.8001G and 1.7999G will be observed. And the injection locking may occur if the injection is strong enough. How to simulate this?
Thanks!

Title: Re: VCO pushing and pulling simulation
Post by Ken Kundert on Jun 27^th, 2006, 2:18pm

If you have SpectreRF you can perform a PSS/PAC analysis and use that to compute the coefficient of pulling. But this assumes a small interferring signal. You cannot use this approach to determine when injection locking occurs. For that you would have to use a transient analysis, which of course is an expensive simulation.

-Ken

Title: Re: VCO pushing and pulling simulation
Post by zzphht on Jun 27^th, 2006, 3:26pm

Thank you so much, Ken!
The small injection assumption is fine. Actually, I have tried PSS+PAC, but it looks like I can only get one spur.

Title: Re: VCO pushing and pulling simulation
Post by Ken Kundert on Jun 28^th, 2006, 12:29am

If you use PAC, then the signal is injected at the 0th sideband, which is say at 1.8001GHz, then the lower sideband would actually be the -2 sideband at -1.7999GHz. It's got to be there because if you perturb an oscillator the response will primarily be in the phase, and you need both sidebands for phase modulation.

-Ken

Title: Re: VCO pushing and pulling simulation
Post by zzphht on Jun 28^th, 2006, 11:17am

I got it. Thank you!

Title: Re: VCO pushing and pulling simulation
Post by vivarf on Sep 22^nd, 2013, 3:59am

Hi Ken, you mentioned that we can observe the injection locking occur. Could you advise how to do that with transient simulation. I design a injection locked VCO at 30 GHz with injection source at 10 GHz (third harmonic injection). Whatever frequency is injected (even at 5 GHz), the output frequency is always at 30 GHz (free-run oscillation frequency of the VCO). I run transient simulation and do dft to check the spectrum. Thanks.