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# rE Field in HFSS

#### Tures_s

##### Newbie
Hello everyone, I am trying to understand what the rE field is in HFSS, by definition in the HFSS Help it is described as: " The selected component of the radiated electric field, which is multiplied by the radial distance, r."
I don't understand what concretely is for HFSS the radial distance, maybe is it the distance between the wave port and the reference system that I set in Radiation -> 3D for the far field?

Hi,

'r' in this case would be the distance between the phase center of your antenna and a point in the far field.

Note that in the far field, electric field falls off with 1/r, so when you multiply by r, the entire quantity r*E is no longer dependent on r, but instead just on phi and theta.

The practical utility of this far-field quantity is that it can be divided by R in meters to get the E field strength at a point in the far field (useful for a rough idea of things like 3m emissions).

The relationship between r*E [V] and E field (V/M) is similar to the relationship between EIRP [W] and power density [W/m^2]. Note that both are a function of the particular input power being applied to the antenna.

Hope this helps,
--Eric