Radiating patches with low mutual coupling for antenna arrays

Microstrip antenna arrays such as phased arrays and retrodirective arrays are often employed in wireless communications systems to achieve high communication link gain with low profile and cost. The antenna gain will increase with the number of array elements. Consequently, the design complexity will also increase due to interactions among the radiating elements. The strength of interaction is measured by mutual coupling whose presence always degrades the array performance. Mutual coupling reduction can be achieved by filtering using periodic structures but this will make the design more difficult especially with the constraint of limited space. In this paper, the patches have been modified with a higher degree of design freedom in performance optimization while maintaining low mutual coupling. The electric field is concentrated at the centers of two radiating edges. By moving the radiating edges to the center of patch, the physical distance between the radiating edge and the neighbor one is increased with fixed element spacing. In order to demonstrate the usefulness of the proposed design, a dual-fed wideband stacked patch antenna employing the proposed element has been designed. Experiments are performed to verify the simulated results. Due to its excellent electrical characteristics, the proposed radiating element finds applications in large antenna array systems.