2
\$\begingroup\$

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.

\$\endgroup\$
  • 2
    \$\begingroup\$ Each point in a polar coordinate system is specified as the angle φ and radius r from a center point. \$\endgroup\$ – George White Feb 14 '14 at 7:07
0
\$\begingroup\$

For a compound box antenna the formula is similar and this might be useful: -

enter image description here

Obviously they are not using A and B to denote the aperture dimensions but, I suspect that "r" is going to be exactly the same i.e. distance between centre of aperture and measurement point.

\$\endgroup\$
  • \$\begingroup\$ Thanks! Thats what my intuition was just didn't make any sense to me to depend on radius because the units for radiated power are in Watt/steradian not W/m^2 \$\endgroup\$ – RBF06 Feb 14 '14 at 18:17
1
\$\begingroup\$

Spherical coordinates are normally denoted by r, Θ, and φ. Your equation is in terms of those coordinates. r is the distance from the source origin (horn antenna) to the point given by the values of r, Θ, and φ. Thus you already have the answer to your question.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.