Miniaturized open-ended radiator based on waveguide filled with uniaxial negative permeability metamaterial

The recently introduced concept of waveguide miniaturization using a uniaxial negative permeability metamaterial is extended to the design of a miniaturized open-ended radiator. The reflection coefficient and radiation pattern of such an antenna are investigated numerically and experimentally. The experimental prototype comprises an open-ended evanescent waveguide with a cross-section of 0.2λ×0.2λ. The waveguide is filled with negative permeability uniaxial metamaterial based on double-ring resonators in the 7 GHz band and excited with a specially designed probe. The measurements reveal an H-plane radiation pattern with 3 dB beamwidth of approximately 100° and return loss of 13 dB across an operating bandwidth of 5%.