Superdirective Circular Arrays of Electric and Huygens Dipole Elements

Uniform circular arrays (UCAs) provide both omnidirectional (360°) and directive (sector) coverage of the azimuthal plane. Superdirective versions with unidirectional, high front-to-back ratio (FTBR) properties could provide the radiated field characteristics being pursued for NextG wireless networks and their perceived applications. Typical UCA configurations – full, semi-circular, and sector – that radiate vertically-polarized (VP) fields and are composed of either omnidirectional electric dipole elements or unidirectional Huygens dipole elements are analyzed first with conventional methods as reference cases. These omni- and uni-directional element configurations are then treated with several optimization techniques: the classic Rayleigh-quotient (RQ) method and its unidirectional-constrained version; the eigenbeam decomposition and synthesis (EBDS) technique used to design superdirective acoustic receiving arrays; and the Bessel-azimuthal multipole (BEAM) approach developed herein. Several arrays are identified as being superdirective with extremely high FTBR values. The performance characteristics of the arrays of unidirectional elements are demonstrated to be superior in general. Moreover, it is shown that larger radius arrays with RQ-specified excitation amplitudes are robust to changes in them whereas the outcomes of the corresponding small radius versions are not. On the other hand, the BEAM-optimized densely-packed small-radius superdirective arrays are quite tolerant to those variations while generating unidirectional pseudo-needle beams.