what are lumped ports
akedar said:
in hfss size doesnt matter because lumped port just define the type of excitation....b/w the ports so not to worry abt the size
akedar:
Your statement really depends on your application. If you want an excitation for a small body at low frequency, then I would agree that the error introduced by using a lumped port is small enough that it can be neglected for practical purposes.
But for most practical microwave design, I believe this is not true.
For example, try taking a 50 ohm transmission line on 100 um GaAs substrate. Simulate this example as a reference result.
Next, slice a 100um long section from the middle, and put a lumped port on each side of your gap. Simulate this example (1 waveport on each end, and then the 2 lumped ports in the middle). Simulate a 100um section of the transmission line in another example (you will need to use reference planes from the larger original problem so that you don't get your waveports too close together).
Cascade the results of your 100um transmission line with the lumped ports from the 4-port example, so you get a model that should be equivalent to the longer, non-segmented transmission line.
This example is similar to the case on an IC where you want to simulate circuitry on both sides of the transistor.
I think you will agree that lumped ports do indeed have limitations if you use them in situations where the error that they contribute to the problem negates their value in modeling.
--Max