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Simulators >> RF Simulators >> about Mixer Simulation (raise time of LO)
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Message started by Muhammed on Jun 11^th, 2012, 10:42am

Title: about Mixer Simulation (raise time of LO)
Post by Muhammed on Jun 11^th, 2012, 10:42am

How much raise and fall time should i put when i make simulation of Mixer .. i am using rail to rail square pulse ???

Title: Re: about Mixer Simulation (raise time of LO)
Post by RFICDUDE on Jun 11^th, 2012, 4:34pm

Well ...
What really matters is the rise/fall time of the buffers that will actually drive the capacitive load of the mixers switches. It is not a good idea to drive the mixers with ideal voltage waveforms with finite rise/fall times because ultimately the rise/fall times are limited by the driver slew rate and parasitic capacitance.

Title: Re: about Mixer Simulation (raise time of LO)
Post by Muhammed on Jun 11^th, 2012, 5:05pm

ok .. so How much rise/fall time should I put when I simulate the mixer itself without buffers ??? I am using tsmc13rf tech file in cadence .. is there any data i can get about this ??

Title: Re: about Mixer Simulation (raise time of LO)
Post by RFICDUDE on Jun 11^th, 2012, 7:13pm

What are you trying to emulate by setting the rise/fall time?

An ideal voltage source will drive the gates without any consideration for the capacitance load of the gates; therefore, the rise/fall time of the voltage source (I assume you are driving the gates with a voltage source) is meaningless.

You need a buffer; otherwise, what are you trying to model by using the rise/fall time?

Title: Re: about Mixer Simulation (raise time of LO)
Post by Muhammed on Jun 12^th, 2012, 12:52am

I want to see the effect of rise/fall time of LO on mixing action .. so i want to roughly rise/fall time to LO voltage source .

Title: Re: about Mixer Simulation (raise time of LO)
Post by RFICDUDE on Jun 12^th, 2012, 4:02am

Ok, then I would sweep the rise/fall time to see the impact on mixer conversion gain/loss, linearity and NF.

The maximum rise/fall time should be fast enough for the pulse to transverse from 0 to the supply voltage and back down to 0 for the shortest pulse width you need (i.e. highest LO frequency).