Difference Between Incident Voltage and Total Voltage

[matheusraugustinho]

Hi guys,

I'm simulating an antenna on the HFSS driven terminal (Lumped port) and I've come across the following situation:
In edit sources, when using incident voltage, the Incident, accepted and radiated power quantities are altered when I change the impedance of the port. In other words, I can see the amount of power absorbed by the antenna depending on the impedance match.
This is not the case when I use the total voltage. In this case, when I change the impedance of the port, only the incident power changes, and the accepted and radiated powers remain fixed.
I would like to better understand this phenomenon and the difference between the two forms of excitation.

Thanks

 

[volker@muehlhaus]

This is not the case when I use the total voltage. In this case, when I change the impedance of the port, only the incident power changes, and the accepted and radiated powers remain fixed.

Do you agree that the physical input impedance into the antenna is the same, no matter what port impedance you have chosen for simulation?
Then if that load impedance is fixed, and the voltage across the load is fixed (total voltage), the power into the load (antenna) is also fixed. So indeed, accepted and radiated power don't depend on port impedance if the voltage at the antenna input is fixed.

Does this make sense?

 

[matheusraugustinho]

Hi,

I think that make sense.

So, the accepted and radiated power is measured considering only load of antenna? The voltage across load don't depend of port impedance?

 

[volker@muehlhaus]

From your initial post I understood that your setup uses fixed port voltage, and then power accepted by the antenna depends on antenna impedance (=Zload).

The source power of the port can vary, due to impedance mismatch if Zport is different from Zload.