Extremely low profile wideband UHF antenna

This research analyzes the properties of anisotropic magnetic media used to reduce the profile of a radiating rectangular cavity at low UHF. Traditionally, air-filled rectangular waveguides achieve broadband performance via a coaxial line-to-waveguide transition which terminates in a tuning element. The waveguide is terminated in a short below the tuning element. Usually the electrical height between the tuning element and the short is approximately one quarter the guide wavelength. We propose loading this portion of a waveguide with high index anisotropic media to reduce this height. Furthermore, we explore the concept of a low profile radiating waveguide at low UHF by also minimizing the distance between the tuning element and the radiating aperture. The aperture is the opening of our cavity surrounded by a one inch flange. At this point, the structure is more accurately described as a cavity rather than a waveguide due to its being a very small fraction of wavelength. We use a transverse resonance condition established between the walls of the cavity and the anisotropic medium to suppress the introduction of high order resonances introduced by the high refractive index of the medium. We derive this transverse resonance condition for the anisotropic case and apply the results to the design of our cavity.