The split ring resonators (SRR) is designed to work at X band and its equivalent medium parameters are estimated by using the equivalent analysis method. The high gain microstrip antenna, which is based on Photonic BandGap (PBG) structure, is also studied. To make the scattering wave deviates mirror direction and reduce the out-band Radar Cross Section (RCS) without affecting the performance of antenna, the designed SRR is used as the cover of PBG structure microstrip antenna. The results show that the forward gain of PBG structure antenna is 0.8 dB higher than the tradition antenna. After the SRR covers on the PBG structure antenna, the gain of antenna is unchanged and the RCS of the mirror direction decreases for all incident angles, and the most decrement is 21.05 dB.
