Two-element superdirective array antenna composed of high-Tc superconducting small helical radiators

Superconductors offer the potential for achieving highly efficient small and/or superdirective array antennas. This paper describes the design and reports experimental results for a two-element superdirective array antenna fabricated with YBaCuO superconducting material. 0.05λ helical radiators and quarter-wave matching and branch circuits were designed for an array antenna with a 0.09λ radiator spacing, to obtain a superdirective radiation pattern at 900 MHz. The array antenna thus fabricated realized good impedance matching and higher radiation efficiency than a Cu antenna, and a unidirectional radiation pattern at 80 K and around 900 MHz.