Isolation Enhancement between Two Dual-Band Microstrip Patch Antennas Using EBG Structure without Common Ground Plane

Abstract

In order to enhance the isolation level between two dual-band E-slot microstrip patch antennas, EBG structure which operates in UMTS Tx(1.92～1.98 GHz) and Rx(2.11～2.17 GHz) band is proposed. The proposed EBG structure made with a periodic array of two different size EBG unit cells which has a modified mushroom-type for isolation improvement between two antennas. They do not share a common ground plane of the microstrip patch antenna. Overall size of the fabricated antenna is 210.5 mm×117 mm. The two different EBG unit cell sizes are 15.6 mm×4 mm and 17.4 mm×4 mm, respectively. It was etched on the FR-4 substrate(thickness=3.93 mm, εr=4.6). The experiment results show that the isolation level between antennas in Tx/Rx band were improved by about 9 dB and 12 dB, respectively, through the use of the proposed EBG structure.