Miniaturized Circular-Waveguide Probe Antennas Using Metamaterial Liners

TL;DR

This paper introduces a miniaturized circular-waveguide probe antenna with metamaterial liners that enable operation well below natural cutoff frequencies, achieving high gain and efficiency in a compact design.

Contribution

It presents a novel miniaturization technique using metamaterial liners and a new feeding method to efficiently excite the HE11 mode in a compact circular-waveguide probe.

Findings

Achieves 42% below natural cutoff frequency

Provides up to 28.8% radiation efficiency

Uses a simple printed-circuit metamaterial liner

Abstract

This work presents the radiation performance of open-ended circular-waveguide probe antennas that have been miniaturized by the introduction of thin metamaterial liners. The liners introduce an HE$_{11}$ mode well below the natural cutoff frequency, which provides substantial gain improvements over a similarly sized waveguide probe. A new feeding arrangement employing a shielded-loop source embedded inside the miniaturized waveguide is developed to efficiently excite the HE$_{11}$ mode and avoid the excitation of other modes across the frequency reduced band while maintaining the antenna's compactness. A metamaterial-lined circular-waveguide probe antenna operating over 42% below its natural cutoff frequency is designed to provide a radiation efficiency of up to 28.8%. A simple, printed-circuit implementation of the metamaterial liner based on inductively loaded wires is proposed and its dispersion features are discussed.