HFSS Lumped Port Impedance for Matching

Hello all--

I am looking to match an antenna design to an RFIC. I initially matched the antenna to the lumped port set to 50 ohms. I then changed the lumped port to the RFIC's impedance (63-j199), resimulated, and saw no difference.

What am I missing?

Thank you,

Dave

There should be some difference:

Zo =50;
ZL=63-j*199;
Reflection Coeff = (ZL-Zo)/(ZL+Zo)

= 0.7842 - 0.3800i

RL = -20*log10(abs(0.7842 - 0.3800i))
= 1.1953

You should see atleast 1 to 2 dB difference, after you changed the impedance of RFIC.

-sv

Hi CDWest
Lumped port connecting only to one point but the input have width so it's not accurate. use face port or wave port it's better
look also at this examples. the ic is in the middle. look also at the concept of feeding.

Plasma

Thanks SV,

Agreed. ... I usually need a huge inductor to match these chips. I see a very small difference in the input impedance (0.0001 delta), but nothing material (probably difference in the mesh).

The only thing I've changed is the Lumped Port defition. Images attached, if they're any help. Matching elements from left to right are: series-finite conductivity (copper), shunt-2.8pF, series-3nH, shunt-open. Port on left, antenna on right.

matching_network.jpg
smith_50.jpg
smith_63-j199.jpg

Hi Plasma,

Thanks for the references. I'm working on a tag with a variety of other circuitry over a ground plane, so I'm trying to save space by matching with passives. I have been asked to provide simulation results with the chip impedance represented. The feed line is about lambda/50 in length, so I'm not too worried about its characteristic impedance... should I be at this size?

Thanks,

Dave

This is about the antenna matching use lumped port.