circularly polarised transmit-receive antenna

Hi
I am doing a project on the design of circularly polarised microstrip patch antenna.The requirement is to design a single antenna for both transmitting and receiving. Is it possible to use circularly polarised nearly square antenna with dual feed(one for RHCP and other for LHCP)?which feed can i use(probe or aperture).I heard that two circularly polarised feeds to square antenna will produce linearly polarised antenna.Is it correct?
My requirement is to produce a pencil beam?Should i use array for that or is it possible with single antenna?
Please anyone give me the suggestions..

Pencil beam is a x-y array.

You can get circular polarization from feeding a patch in the corner with a single feed line or you can use a hybrid to feed for circular.

This should teach you everything:
http://www.kyes.com/antenna/antennadex.html