antenna-theory.com

[dnyberg2]

I understand what EIRP is, but I see that it is mostly calculated using the PWR input and the gain of an antenna. What about the radiation pattern? A polar plot of radiated PWR? Isnt that the best right way to verify the EIRP value and direction of maximum PWR?

[bigSteve]

EIRP is a measurement of power transmitted at a single direction relative to an antenna. So if you have a known transmitted power from a source antenna (P1), and a known pathloss (L), then the received energy is the EIRP.

When you say it is calculated using input power and gain, you are probably referring to peak EIRP - that is, the maximum EIRP in the direction of the antenna's maximum radiation. But note EIRP can be measured around the entire sphere, and this information can be used to calculate the gain and directivity of the antenna.

The radiation pattern is the angular variation of EIRP around the sphere. It can be plotted in polar form, as a function of polar angle, azimuth angle, or a spherical 3D plot. It simply tells you how the radiated power varies with direction from the antenna.



EIRP on this webpage is defined here, if you haven't seen it:
http://www.antenna-theory.com/definitions/eirp.php

[dnyberg2]