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Simulators >> RF Simulators >> Simulation of Mixer Common Mode in Cadence
https://designers-guide.org/forum/YaBB.pl?num=1341496774

Message started by DDC on Jul 5^th, 2012, 6:59am

Title: Simulation of Mixer Common Mode in Cadence
Post by DDC on Jul 5^th, 2012, 6:59am

Hello,

I want to simulate the influence of the common mode voltage of my mixer. It is a standard gilbert cell, but the problem is, I cant simulate CMRR because of the periodic variing operation point of the switching transistors. Has somebody an idea, how I can simulate it ? I think I have to use pss analysis, but it is not clear for me. Thanks for response.

Title: Re: Simulation of Mixer Common Mode in Cadence
Post by RFICDUDE on Jul 5^th, 2012, 5:56pm

PSS with PAC will tell you what you want to know.
I assume you are interested in knowing the common mode input (at some frequency) to the common mode output at some other frequency?

With PSS/PAC you can sweep the frequency of a common mode input and measure the common mode or differential mode responses around harmonics of the pss fundamental frequency.

Title: Re: Simulation of Mixer Common Mode in Cadence
Post by DDC on Jul 6^th, 2012, 4:01am

Can you describe, what setup at the ports (LO,IF,RF) I have to apply ? I use an rf frequency of 2.4 GHz and and lo frequency of 2.37 GHz. Do I sweep the rf frequency and which port contains the PAC magnitude ? It's not really clear for me. Thanks for response.

Title: Re: Simulation of Mixer Common Mode in Cadence
Post by DDC on Jul 6^th, 2012, 4:03am

I use a CMFB circuit, I want to know for which input powers my CMFB works well. What Simaltion Setup I could use ?

Title: Re: Simulation of Mixer Common Mode in Cadence
Post by RFICDUDE on Jul 6^th, 2012, 4:52am

You keep the LO frequency constant and sweep the RF input frequency. The PAC sweep can be set up in one of two ways: either absolute input frequency or "relative" to the PSS fundamental. I find it easier to use an absolute input range.

The output will contain many sideband results from the different harmonics of the LO, but one of them will be the frequency conversion response that you are looking for. If this is a downconversion mixer then you are most likely interested in the -1 sideband response (RF to IF or BB).

I suggest running a PSS/PAC simulation in differential mode first to make sure the set up is correct and you are simulating the correct conversion gain. Then change the input to be common mode and repeat the simulation to measure the common mode gain.