how to set even- and odd-mode excitations in HFSS? - RF Cafe Forums

 Post subject: how to set even- and odd-mode excitations in HFSS?

Posted: Mon Jan 23, 2006 7:41 am 

Hi all,

I have been recently trying to simulate a pair of coupled striplines in HFSS. I tried but failed to obtain the coupled lines' characteristic impedance and relative dielectric constant for even-mode (Zoe, Epsilon-re)and odd-mode (Zoo, Epsilon-ro) excitations.

I set two wave ports on two ends of the coupled lines. In each port, I set two terminal lines so that I could use the terminal lines' directions to represent the even-mode and odd-mode. But in this way, even though there were still two wave ports, the S-parameter I obtained was a 4-port one but not my wanted 2-port one. Besides, from E-field distribution, I found the above way couldn't seperate the even- and odd-mode. The E-field distribution for same terminals' directions is almost same as that for opposite terminals' directions.

Does anyone know how to use HFSS to simulate the coupled striplines or make even- and odd-mode excitations? would you please give me some advice and tips? I greatly appreciate your precious assistance.

 Post subject:

Posted: Tue Jan 24, 2006 1:37 pm 

there are examples in the training material. Basically, what you need to do is to go to HFSS->Excitations->Assign

Depending on the port/solution type, you can adjust the amplitudes of each port

 Post subject:

Posted: Wed Jan 25, 2006 3:34 pm 

I don't think the previous answer understood the question - what you have to do is allow more than one mode per port. Then look at the fields in a port-only solution - one of the modes should be even, and the other should be odd. If you do a ports-only solution, you will be able to see the impedance for each mode. Then, for transmission, you only have 2 ports, but each will have 2 modes, so you have S-parameters like P1M1-P2M2 (port one mode one to port 2 mode 2) etc, etc.