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RFIC design: problem with FEM ports definition

Question asked by Falcon on Apr 13, 2015
What is the correct way to define TML calibration ports, when using the same ground metal for multiple transmition lines?
I am designing a distributed amplifier, I am using the lowest metal (Metal1 in this example) for ground and the top metal for the transmission lines (I attached a picture to better discribe the setup).
I am using the differential ports to set Metal1 as ground - for each port I set two pins - one targetting the Metal1 and second targetting the TopMetal and then I set the pin targetting the Metal1 to be negative potential for the pin targetting the TopMetal. I do this for all the 4 ports. With this setup I chose the resulting ports to be TML zero length (because I want no extra inductances added).
If chose Momentum simulation, I get an error saying:
"A calibrated pin must not be positioned on an edge on which other pins are positioned. (Using a single calibrated pin simultaneously in several ports is also invalid in this respect.) The pins involved are "P#" and "P#""
If chose the FEM simulation, I get “triangle ports” and warning saying: “Calibrated port P2 and port P4 are in almost identical reference planes. Still the reference planes are sufficiently misaligned, prohibiting ports to be co-calibrated or to become part of the same waveguide. Adjust the ports to exactly share single reference plane if co-calibration or waveguide behavior is desired”.
Further on if I make the pins to be edge/area pins and make the ports out of them, that solves the “triangle ports” problem, but for each port I get a warning saying: “Calibration will not be used for port P1 (pins P1 and P5 are not on the edge between a conductive and not conductive region)”

Edited by: Falcon on Apr 14, 2015 5:49 AM