Electromagnetic Characterization of a Two Element Square Spiral Printed Antenna on FR4 for the 5.8 GHz Band

Abstract

This paper investigates bandwidth enhancement of a hexagonal microstrip patch antenna using a hexagonal aperture in the ground plane. A full-ground antenna (HMPA) and a slotted-ground antenna (SMPA) share a 55 × 56 mm² footprint and a 1.6 mm Megtron 6 substrate. Their −10 dB impedance bands extend from 12.30 to 13.65 GHz and from 11.76 to 15.04 GHz, respectively. With the band midpoint as the reference frequency, the corresponding fractional bandwidths are 10.40% and 24.48%. The slot increases absolute bandwidth by 1.93 GHz while retaining the same radiator and feed dimensions. At approximately 13.25 GHz, the reported realized gain changes from 2.43 to 4.52 dBi; the sidelobe level changes from −12.8 to −1.4 dB. Reflection-coefficient, VSWR and simulated current distributions are used to discuss the broadened match and its radiation trade-off. The results show that a single ground aperture can broaden the impedance response of a compact Ku-band patch, although radiation-pattern quality must be considered alongside bandwidth.