Hexaferrite Substrate Versus Impedance Matching for Tuneable Patch Antenna Miniaturisation

Abstract

Novel hexaferrite substrates and impedance matching networks are both means to deliver electrically small antennas (ESAs). The performance characteristics of each are often restricted to a discussion on the reflection coefficient S11, without consideration of full radiative characterisation. In this work the radiation efficiency and pattern of a hexaferrite patch ESA and impedance-matched sub-resonant Rogers RT5880 patch were compared. The efficiencies of each technique were found to be low, while the pattern of the sub-resonant patch displayed considerable divergence from the half-wavelength behaviour of the hexaferrite patch. The stability of the magnetically-tuned radiation pattern of the hexaferrite patch was then demonstrated over a tuned bandwidth of 32.1%.