The conventional pyramidal horn antenna has been used for microwave applications for a very long time. Its gain can be increased by enlarging the construction of the horn to flare exponentially. This paper intends to present a method for gain enhancement of conventional pyramidal horn antenna in the frequency range 2.2GHz to 8GHz using Electromagnetic Band Gap (EBG) without construction enlargement. It has been proved that proper utilizations of EBG structures can enhance the performance of low profile antennas. So here a new EBG technique, which is the modified version of mushroom-like EBG structure, is employed in the pyramidal horn antenna.