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Hi ,

How can i find the dimensions of the HFSS wave port?.
I know that it exist a calculator to do that in www.emtalk.com and for 50 Ω TL only, but i want to determine the size manually for TL feed not 50 ohm.
is there any exact rule ,i've read a HFSS doc but i'm not convinced when comparaing with results of my simulation.

help please.

thanks

You can use the 50ohm port size, then choose "Solve ports only" (in solution setup), and check the results to make sure the right modes are propagating. The necessary port size does not change much when impedance changes, and "Solve ports only" is more reliable than the calculator even for 50ohm.

halo i am new to hfss and actualy am confused about how to size the wave port now what i do is once i have calculated the microstrip line width i use the wave port claculator at emtalk to find the wave prt dimension than i use sole port only to find Z0 appearing at the port .after this i optimize Zo at the port to 50 ohm by changint the waveport dimension after that i change the line width to get 50 ohms at wave port and the optimization is done using ports only.

the results are better but now i need opinion if the method i am using is right or not ? also how can i check in hfss that unwanted modes are not appearing at the port ?

You need to define the port so that it supports multiple modes. After simulating, check HFSS->Results->Solution Data to see if just one mode propagates. Then, you can make the port bigger, which will make it a little more accurate (captures more fringing fields) as long as no second mode appears.

"after this i optimize Zo at the port to 50 ohm by changint the waveport dimension" - if I understand correctly, you are not changing real Zo, you are just creating an error in the simulation which offsets the deviation in physical Zo for your structure. Seems like a recipe for trouble. Better to rely on mode propagation to verify the port, rather than changing the port size this way.

But really, the emtalk results should be relative accurate from the beginning. (I haven't checked them, but there is no one exact port size that you must use. Even if emtalk's size is not ideal, the error caused is probably small.)

Hi Leaps & Shlomo22,

I agree with Shlomo22, you have to look for the propagating modes and you should not change the wave port size arbitrarily.Work out the example N° 6.5 from HFSS Guide Book ,you will understand how to find the port size and have a look to HFSS docs about this.Don't rely on emtalk calculator i've used it but with worse results.

Hope that helps.

in the solution data after simulating how can i study what modes are being produced kindly can anyone explain in simple words ?

PS:
in my HFSS > RESULT > SOLUTION DATA in the matrix data section i am getting Zo at 10 GHZ is 49.9 is ths the value i need to chk ?

Pl tell how can i study what modes are being produced from matrix data? Thx

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