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Design >> RF Design >> How to simulate Mixer using Spectre?
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Message started by blilix on Aug 2^nd, 2006, 12:23pm

Title: How to simulate Mixer using Spectre?
Post by blilix on Aug 2^nd, 2006, 12:23pm

Hi,
I am working on Down conversion Passive Mixer and want to know the right way to simulate the voltage conversion gain of it. I read the cadence manual and it describes about the PSS and PXF or PAC to simulate the conversion gain. However, somebody told me to use only PSS analysis. What is the right way to simulate this?

Best regards,

Title: Re: How to simulate Mixer using Spectre?
Post by simon2 on Aug 2^nd, 2006, 3:33pm

Hi Blilix,
I know of no "right way" to simulate mixer voltage gain - there are many and they have different meanings. However, arguably the most meaningful would be to calculate the output power divided by the input power. Notice that such power terms are frequency independent, which suggests a way to do it for voltages, by carrying out the calculation using the envelope of the input and output waveforms via the geometric identity x=((cos(y))^2+(sin(y))^2)^0.5.

Rather than explain it all here, have a look at:

http://www.silicondevices.com/Resources/AppsNotes/MixerGainSimulation.html

which is incomplete (need a real example added) but does explain the method.

Cheers,
SimonH.

Title: Re: How to simulate Mixer using Spectre?
Post by ACWWong on Aug 3^rd, 2006, 3:14am

blilix wrote on Aug 2^nd, 2006, 12:23pm:

PSS+Pxf and PSS+Pac will give you the small signal gain under frequency translation of the Large LO tone.

using straight PSS to get the gain will mean the RF input is no longer a small signal input, but if its within the linear region of operation of operation of the mixer it will give the same result as PSS+Pxf or PSS+Pac, much in the same way as a transient simulation would. Of course there is a compuational overhead for doing two tone (RF &LO) PSS or transient in comparison to PSS+PAc or PSS+Pxf, especially if the down converted IF is much lower frequency than that of the LO....

To capture compression effects on gain due to large RF inputs, then PSS, transient or QPSS (the results of each should be similar) would be more appropriate than small signal analyses pac or pxf.

hope this helps...

Title: Re: How to simulate Mixer using Spectre?
Post by blilix on Aug 5^th, 2006, 9:45pm

Thank you so much everybody.