Low-profile Super-Realised Gain Antennas

This study introduces an novel approach to the design of low-profile superdirective antenna arrays, employing parasitic elements. The proposed design concept was verified through the analysis of a two-element antenna array consisting of strip dipoles, operating at a frequency of $3.5$ GHz within the sub-6 5G frequency band. The antenna array was optimized for realized gain, a key antenna parameter considering both ohmic and return losses. The design parameters included the lengths and widths of the strip dipoles, along with a reactance load connected to the parasitic element. The driven element was excited by a sinusoidal voltage signal with a magnitude of $1$ V, eliminating the need for amplifiers, attenuators, phase shifters, or impedance matching networks. Results demonstrated that this design concept enables the achievement of superdirectivity, with inter-element distances as small as $0.1\lambda$, resulting in low-profile, compact, high directional antenna systems.