Ok This might sound dumb but I am trying to get an equation for the radiation intensity of a pyramidal horn antenna in spherical coordinates. I got a whole bunch of books and they all have the same equation: $$\mathbf{E}_\theta = \frac{j\, e^{-j k r}\, E_0\, A\, B\, (1 + \cos(\theta))\, \sin(\phi) ...}{8\, \lambda\, r}$$ $$\mathbf{E}_\phi = \frac{j e^{-j k r} E_0\, A\, B\, (1 + \cos(\theta)) \cos(\phi) ...}{8\, \lambda\, r}$$

Ive got like 4 different text books about the subject and the all of them have those exact same equations. But not a single one says what $r$ is anywhere. Anybody know what this is?

Sorry to ask but I've been searching for hours. Can't find a single source that explicitly says what $r$ is.

• Each point in a polar coordinate system is specified as the angle φ and radius r from a center point. – George White Feb 14 '14 at 7:07