How to design ROD antenna?

Hi friends
How to design rod antenna for 5.8GHz?
I want to use it as transmitter as well as receiver.
transmitting power is 9dBm.
receiving power is very low.
please help me for designing it.

do you mean dielectric rod antenna?
If so, what shape have you chosen (rect, cyl, etc.)?

If you mean what i wrote, do some background
reading in the book by Kajfez 'Dielectric Resonators'
happy designs!

Its simple rod ( tapered at one end)
It will be used in radar.
Thanks for your suggestion