How can I calculate the axial ratio of an antenna?

Hi to all,
Can anyone tell me, how can I calculate the axial ratio of an antenna, employing the theta and phi components of the electric field vector?

Thanks to all.

Here is an excellent reference:

Amazon.com: Polarization in Electromagnetic Systems (Artech House ...The only clear exposition of the effect of polarization on electromagnetic ... Antenna Theory and Design, 2nd Edition by Warren L. Stutzman on 5 pages ...
http://www.amazon.com/Polarization-E.../dp/089006508X - 179k - Cached - Similar pages

Without knowing the details of yor situation I am reluctant to give you a "formula". This is a subject that comes up regularly on the forum. Some of it is on target and some is confusing at best.