Miniaturized Circular-Waveguide Probe Antennas Using Metamaterial Liners

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.Comment: The manuscript has been revised for publication as a 6 page communication in the IEEE Transactions on Antennas and Propagation. This included a reduction of material in the theory section, removal of all discussion on anisotropic theory, and introduction of a novel excitation sourc

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Gas chromatograph injection system

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