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Simulators >> RF Simulators >> Mixer NF with swept LO simulation problem
https://designers-guide.org/forum/YaBB.pl?num=1090451801

Message started by Rehan Zakai on Jul 21^st, 2004, 4:16pm

Title: Mixer NF with swept LO simulation problem
Post by Rehan Zakai on Jul 21^st, 2004, 4:16pm

I am working on a direct conversion mixer and I need to plot NF at a fixed baseband frequency as a function of swept LO frequency. Does anyone know how QPSS and QPNOISE analyses should be setup?

I have tried to setup LO frequency as a swept design variable for QPSS analysis and performed a single point QPNOISE analysis but that does not produce correct results. Is there anything I have to do out of the ordinary when setting up the analysis?

Thank you in advance.
R. Zakai

Title: Re: Mixer NF with swept LO simulation problem
Post by August West on Jul 22^nd, 2004, 8:44am

I don't have any suggestions on how to sweep the LO frequency, but it strikes me that these two analyses are overkill in this situation. If you want the NF with only the LO applied, you should be able to use PSS and PNoise.

-August

Title: Re: Mixer NF with swept LO simulation problem
Post by Rehan Zakai on Jul 22^nd, 2004, 9:03am

Since this a narrow band direct conversion mixer, the beat frequency for PSS analysis is too small practically. QPSS analysis is better suited to handle these types of circuits. My understanding is when beat frequency for PSS analysis is less than 1/10 of the LO frequency, QPSS is more practical solution.

R. Zakai

Title: Re: Mixer NF with swept LO simulation problem
Post by August West on Jul 22^nd, 2004, 9:32pm

But you don't have a beat, at least in a large-signal sense. The only large signal applied is the LO, so you can use PSS & PNoise.

-August

Title: Re: Mixer NF with swept LO simulation problem
Post by Rehan Zakai on Jul 29^th, 2004, 9:19am

Just to close on this issue, QPSS analaysis is the only thing to do here, there is a beat, it is equal to the LO frequency and since it varies as LO frequency is swept, PSS analysis does not work. QPSS is easy to setup, I originally has problems due to a scripqting error elsewhere.
Rehan

Title: Re: Mixer NF with swept LO simulation problem
Post by August West on Jul 29^th, 2004, 10:37am

To get a beat you need two large tones. Clearly the LO is one large tone. But what is the other?

If there is only one large tone, then PSS should work.

-August