Cadence Virtuoso portAdapter for Load Pull

Hello,

Im hoping to get some help with using PortAdapter for load pull in Cadence Virtuoso! I am using Virtuoso to simulate a PA and using PSS to sweep input power. The latest MMSIM supports directly the load pull option within the PSS input form, where I am sweeping the input reflection (mag + angle) of the PortAdapter block (which I have borrowed from RFExamples library). I get a somewhat strange result for Zopt which, from reading off the resulting smith chart showing power contours, results in a little red X at reflection coefficient:

Gamma_mag=-0.95 (negative)
Gamma_ph=359.5

(very close, but not quite an RF short)!

Using the Zopt values set into the PortAdapter, I get good compression curve, with over 30dBm OP1db.

However if replace the PortAdapter with a simple LC matching network with appropriate values to give the same impedance, my compression curve drops to less than 15dBm OP1db.

Does anyone have good experiences with PortAdapter?

Thanks for any help!

Gamma_mag can not be negative .I'm sure there is a serious problem..

BigBoss said:

Gamma_mag can not be negative .I'm sure there is a serious problem..

Click to expand...

Yes, I agree. I just tried a simple transistor from my PDK, significantly smaller, and came out to the same result, Gamma_mag = -0.95.. Perhaps it is something wrong with the transistor models in the PDK.

Thanks for the comment!

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micsa said:

Yes, I agree. I just tried a simple transistor from my PDK, significantly smaller, and came out to the same result, Gamma_mag = -0.95.. Perhaps it is something wrong with the transistor models in the PDK.

Thanks for the comment!

Click to expand...

Does anyone know about the other parameters in the callback form for PortAdapter? For example xcomp, ycomp? It seems they reference variables "theta", "rho", "thetaoff", "rhooff"... does the model require that these be the names for the sweep variables?

Hi micsa,

are you using the portadapter the right way?

set frequency as frf, phase as theta, mag as mag, ref resistance as the o/p port resistance. do a pss sweep of theta (0 to 359) and mag from 0 to 1 in parametric analysis (or the other way round).

view results power contours and highlight the optimum power point to look at the real and imaginary values. that's your Zopt. if you want to calculate the reflection, just use the formula thereafter

Best Regards,
Natnoraa

You can't probe after port adapter, this is a known issue in portadapter. try to place your port before the port adapter. also you can use load pull from within pss form...