dipole antenna with refector

i am working on printed dipole antenna.....want to put reflector behind the antenna in order to increase the gain.....don no how to start,....plzz help

What you are doing is building a primitive YAGI aerial. See :-http://en.wikipedia.org/wiki/Yagi-Uda_antenna
Frank

you can add single parabolic dish or arrays of reflector and directors to increase gain

dipoles above various reflectors are a common subject of antenna text books. Try Kraus as a starting point. Maximum gain will be at 1/4 wavelength and the size of the ground plane is not particularly sensitive provided it is not too small.

Azulykit