input impedance of RDRA

hiiii
anyone plz tell me how can i calculate the input impedance of Rectangular dielectric resonator antenna ?
anyone have the formula for input impedance of Rectangular dielectric resonator antenna, plz provide me?
its very urgent ..............

Generally its easier to predict the resonant frequency of an antenna. Which in case of DRA is given by the dimensions of the Dielectric Resonator and by the offset distance from the feed-line.

plz explain me in detail how can i predict input impedance from resonance frequency ?
plz tell me

Can assume that an antenna is a form of a LC tuned circuit and as a result it has a resonant frequency where the capacitive and inductive reactances cancel each other out. At this point the input impedance of the antenna appears purely resistive (a combination of the loss resistance and radiation resistance).

For DRA these documents may help finding the resonant frequency:

http://www.ursi.org/Proceedings/ProcGA05/pdf/BP.24(01233).pdf
http://www.ee.olemiss.edu/darko/dra-pcfaaa.pdf

can u explain it in DETAILS-------------with some reference paper-----------please i need that