Coupled Array of Diverse Elements for Wideband High Spherical Coverage

We propose a flexible cluster array concept utilizing diverse antenna elements and the mutual coupling among them to improve the spherical coverage. This innovative approach can not only enhance the impedance matching but also improve the beamforming performance across a wide frequency band by adjusting excitation amplitudes and phases. Equations are derived to achieve specific objectives such as minimizing the total active reflection coefficient or maximizing the realized gain of an antenna array. To validate the concept, we employ a cluster array consisting of eight non-identical patch antenna elements with strong mutual coupling. When compared to a conventional four-element patch antenna array of the same size, the cluster array exhibits high beamforming capability over a wider frequency band. Simulated and measured results confirm that the operational frequency band can be extended from 24.5–26.5 GHz to 24.5–29.5 GHz, while maintaining a spherical coverage of over 6 dBi at the 50%-tile cumulative distribution function (CDF) of maximum realized gain.