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 λ 0 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.

No abstract

A planar loop antenna producing uniform magnetic fields horizontal to its plane is presented. The antenna consists of a pair of two-turn spiral coils that are sequentially excited. To prevent undesirable magnetic coupling between the coils, a novel coil-switching circuit is proposed, which is automatically operated using the interrogating signal from the reader. The antenna is suitable for a high-frequency radio frequency identification reader antenna installed under a chip tray to monitor gaming chips in a casino.