Learning Forum

[Jean TAPIE]

Hello,

I have done simulations with lumped port and there are things I can't explain.

Bellow is a screenshot of the simulation in which I have a lumped port and rectangles of pec on top and bottom. In the edit source I put 1V (solution type terminal). The length of the lumped port is 0.9mm(bottom to top). After the simulation I evaluated the field Ez in the middle of the port which I supposed the magnitude was going to be 1V/0.9mm=1111V/m but is actually 2222V/m (2*supposed electric field). I did the same simulation with solution type modal with the integration line from bottom to top (0.02W to have 1V with the port 50Ohm), this time the magnitude of Ez was 3142V/m (2*sqrt(2)*supposed electric field).

Do you have ideas why I got those results? I thought maybe it was due to the voltage in the edit source being the effective voltage (for terminal) and the power being effective power (modal) but I did not find an answer in the HFSS Help pdf. 

Regards

 

[Jason.k]

Hello Jean, 

We appreciate reaching out to Ansys Forum. 

The different results you are experiencing when using Lumped ports in HFSS with Driven Terminal or Driven Modal solution types can be attributed to the nature of these solution methods. Driven Terminal and Driven Modal are two different solution types that are using different interpretations. In Modal, Port’s signal decomposed into incident and reflected waves while in Terminal Port’s signal interpreted as a total voltage (Vtotal = Vinc + Vref). 

To convert this total voltage to power we can use this formula: P=V^2/(2*Zo). 

I hope this helps. 

Kind regards, 
Jason.k

[Jean TAPIE]

 

Hello Jason,

Thank you for your answer. 

What you wrote explains the sqrt(2) factor for the modal case. But my main concern is why the electric field is two times the supposed one in both cases (modal, terminal)?

Regards,

Jean