Abstract: A hexagonal focal-plane array of microstrip antennas with electromagnetic bandgap (EBG) structure is proposed. After an in-depth study of EBG structure to suppress mutual coupling between antennas, a hexagonal seven-element microstrip antenna array with EBG structure for reflector antenna is designed and measured. The results show that the EBG structure can suppress the mutual coupling between array elements, improving the matching condition and circular polarization performance of the antenna array. The hexagonal array with EBG structure is competent for the focal-plane array of reflector antenna.