Mutual coupling reduction between closely spaced microstrip antennas by means of H-shaped conducting wall

This Letter presents a novel H-shaped conducting wall structure that effectively suppresses the mutual coupling between two closely spaced microstrip antennas (MSAs). The wall consists of an H-shaped copper strip printed on a dielectric substrate, and a row of periodic vias through which the strip is connected to a ground plane. The wall is inserted between the MSAs and surrounds half the periphery of each antenna. Measurements of a prototype show that the high isolation of about 51 dB is achieved between two MSAs separated by the edge-to-edge distance of 0.052 λ0 at 5.2 GHz. The proposed structure greatly improves the isolation without causing any significant degradation of the antenna bandwidth, gain, or front-to-back ratio, unlike other isolation structures based on resonators or defected ground structures.