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Simulators >> RF Simulators >> Mixer Noise Figure vs LO
https://designers-guide.org/forum/YaBB.pl?num=1121829681

Message started by uncle_ezra on Jul 19^th, 2005, 8:21pm

Title: Mixer Noise Figure vs LO
Post by uncle_ezra on Jul 19^th, 2005, 8:21pm

So I configure PSS to sweep LO from 4.8G to 5.8G with output harmonic set to 0. Then I set Pnoise to do relative to 1 single point sweep @ 1M. For reference sideband I use -1. When I plot the NF it gives me some huge number.

I then run PSS with LO fixed @ 4.8G and sweep Pnoise from 1M to 15M. When I plot the NF it gives me what I expect.

So how to configure PSS and Pnoise to sweep LO signal and plot NF? Also how to configure to sweep LO power and plot NF?

Thanks

Title: Re: Mixer Noise Figure vs LO
Post by Ken Kundert on Jul 20^th, 2005, 12:19am

Did you use a relative sweep? If so you are measuring the noise figure for an up conversion mixer. Is that what you intended?

If you did not use a relative sweep, then your settings look right for a low-side down conversion mixer.

-Ken

Title: Re: Mixer Noise Figure vs LO
Post by uncle_ezra on Jul 20^th, 2005, 2:29am

So for downconversion you dont use relative in Pnoise? You just use absolute? Why is this so?

I tried setting 0 instead of 1 for relative harmonic and the plot looks reasonable. Also for conversion gain plot versus LO I set 1 for relative harmonic in PAC and the result seems right.

So what exactly is relative harmonic, when should you and should not use it?

Thanks

Title: Re: Mixer Noise Figure vs LO
Post by Andrew Beckett on Jul 20^th, 2005, 4:02am

If you sweep the pnoise in relative mode, relative to harmonic 1, it means that you will be looking at the noise at 4.8G+1M to 5.8G+1M.

What relative sweeptype on the small signal analysis does is specify that the frequency sweep you entered is shifted by n times the PSS fundamental where n is the relative harmonic number.

Since with pnoise and pxf you would be entering the output frequency range, this would only make sense with an up-conversion mixer. For pac you're entering the input frequency range, and so it's quite reasonable to use a relative sweeptype there for a downconversion mixer.

From IC5141 USR2 (out soon), the small signal forms have had a minor enhancement that I suggested, which is to add the word "Output" before Frequency Sweep Range on the pnoise/pxf form, and "Input" before the Frequency Sweep Range on the pac form - to make it more obvious to casual users...

Regards,

Andrew.