A parasitic coupling network concept for mutual coupling utilization in wideband multielement antenna arrays

A novel approach to widening the active reflection coefficient (ARC) bandwidth of an antenna array, employing a parasitic coupling network (PCN), is investigated in this article. Different from traditional tightly coupled arrays adopting space structures for enhancing the coupling in balanced-excitation antennas, a PCN derived from rigorous formulas is employed in the feeding lines of unbalanced-excitation ones. Based on network analysis, the mutual coupling utilization condition for an (M×N)-element antenna array is initially deduced, and the PCN is implemented. Then, the PCNs are realized by introducing a parasitic element and a coupling network between the two-element H-plane and E-plane dual-layer coupled microstrip antenna arrays, resulting in 10.9% and 30.8% bandwidth enhancements compared with the original arrays, respectively. Moreover, the PCNs are further expanded to multielement antenna arrays, including three- and five-element one-dimensional and 8×2 two-dimensional arrays, exhibiting approximately 40% overlapped ARC bandwidths with normal radiation patterns, steady gains, and applicable scanning characteristics. The results indicate its potential application in large-scale wideband arrays.