Investigation of anisotropic transverse resonance in the design of low profile wideband antennas

We analyze the properties of effective anisotropic media as a means to reduce the profile of a cavity-backed antenna at low UHF. Many applications in wireless communications and radar require antennas that conform to the surface of a supporting structure. Whenever possible, we wish to minimize the profile of the antenna. Low profile antennas (LPA) are of special importance within the ultra-high frequency (UHF) band where they are used as communications antennas on military platforms.;The antenna under investigation is a flush mounted rectangular cavity with a lambdao/2 aperture opening. We feed the antenna by a two-port matching network fed 180° out of phase at the aperture. In this configuration, the backshort defines the cavity profile, and the backshort should be as small as possible. Our approach loads the cavity with a high index, anisotropic medium to realize a reduction in profile by reducing the distance between the backshort and the matching network. We find this introduces destructive high order resonances by lowering the frequency of lowest resonance established by the separation of the cavity walls.;We derive an anisotropic transverse resonance, and utilize the formulation to design a novel cavity geometry that maintains a constant resonance frequency in the face of high index anisotropic media. The final anisotropic LPA design produces a non-tapered radiating rectangular cavity partially loaded with a magnetic uniaxial anisotropic medium. This LPA achieves a 1.2 octave -6 dB bandwidth and a realized gain ranging from 3.5 dB -- 8.2 dB with a profile of only 0.04lambdao. The non-tapered anisotropic LPA also outperforms other state of the art LPA designs both in terms of bandwidth and realized gain. Furthermore, it performs on par with a typical air-filled radiating cavity both in terms of impedance match and realized gain, but with a 71.4% reduction in profile.