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Simulators >> RF Simulators >> Question on PXF & Transient simulation for mixer
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Message started by James Bond on Jun 8^th, 2007, 12:20pm

Title: Question on PXF & Transient simulation for mixer
Post by James Bond on Jun 8^th, 2007, 12:20pm

Hi, all

I have been stuck by this problem for several weeks, if someone knows this, please give me some suggestion, any commment would be appreciated.

I designed a passive mixer, first I used transient to find conversion gain (Vif/Vrf), it's about the 0.9 times , almost
-1dB; Then I used pss+pxf simulation to verify the conversion gain, I am pretty sure I set the pxf and pss form correctly, but the simulation result shows that the conversion gain is about 20dB, it conflicts with the transient simulation. Could you tell me what will cause this problem?

Thank you very much.
Best Regards
Bond

Title: Re: Question on PXF & Transient simulation for mix
Post by didac on Jun 9^th, 2007, 2:39am

Hi,
Take a look at:http://www.cadence.com/community/virtuoso/resources/SpectreRF_Mixer533AN.pdf to take a look at the pps+pxf configuration just to check it. Also I doubt that doing a Vif/Vrf give you the correct gain in a mixer unless you have filtered the output due to the harmonic components,leakage and other effects.
Good luck,

Title: Re: Question on PXF & Transient simulation for mix
Post by James Bond on Jun 9^th, 2007, 7:58am

Hi,

Thank you for your suggestion. I have checked that doc, and my setting is correct. BTW, the Rf freq is 1.9G, the Lo freq is 1.91G.

I also simulate the core passive mixer individually, the conversion gain is about the -4dB with a capacitive load about 300fF, I check this conversion gain with both transient simulation & pss+pxf, they are coincident; Then I add some other circuit which can achieve extra gain before the passive mixer, then this time, the transient simulation & pss+pxf are not coincident. If the filter worked before, it will also work this time. And I think that the transient simulation will also consider the parasitic filter effect.