Slotline Simulation

I am trying to calculate the characteristic impedance of a simple slotline transmission line.

  1. The numbers I got from MODE does not match that from analytic models. The integration region only includes one strip here since it’s a odd mode. Did not half the impedance got from FDE due to the definition of the characteristic impedance defined in the paper (Z0=V^2/(2P)). Simulation region is 30mm wide and 10mm high. Any idea what could be wrong in this case?

Analytic Model:

Cross section of the slotline

Top view of the simulation setup (blue: substrate; light green: 2D metal strip; small rectangle in the middle: mesh; long line in the middle: FDE simulation region)

Two configfurations are used to correspond to the two lines in Fig.3 in that paper:
Config 1:
W = 40um
D = 400um
Substrate permittivity: 11

Config 2:
W = 800um
D = 400um
Substrate permittivity: 11

Below are the results from the paper and my simulation.

  1. I tried to use EME to measure the S-parameters of a transmission line terminated with a resistor, but the ports do not give modes (while eigenmode solver is able to calculate the mode profile with the same simulation region). All the E field numbers are Nan and H field numbers are 0.

Hi @chm037

Can you please upload your simulation files for a review?


coupled_microstrip.lms (344.9 KB)

please see the file here. BTW, would you please give me your email, so that I can sent that paper to you. I always receive errors when directly reply your email.


Hi @chm037

Sorry for any inconvenience. It seems to be a bug of EME with PEC material. I have reported it and hopefully will be fixed soon.

Thanks for your patience.


And any idea why FDE does not give results matching the analytical model?

Hi @chm037

Can you please check my simulation file and clarify which results do not match with theory?

coupled_microstrip_Modified.lms (246.9 KB)