2 research outputs found
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Transmission-Line Metamaterial Design of an Embedded Line Source in a Ground Recess
A transmission-line metamaterial design of a material-embedded electric line source radiating inside a ground recess is investigated. The media embedding the recessed line source are designed such that the embedded current creates the same radiation pattern as a line source over a flat conducting ground plane. Transmission-line metamaterial unit cell designs for the embedding media obtained from the transformation electromagnetics design technique are shown. The metamaterial design of the overall embedded source configuration is numerically tested using circuit simulations. It is shown that the embedded-source design creates the same radiation characteristics as the line source above a flat ground plane at the design frequency
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Virtual Antennas Using Metamaterials
Virtual antenna radiation at microwave frequencies using metamaterials is presented. Based on the transformation electromagnetics technique, the media embedding a physical antenna in a ground recess is designed such that the far-zone radiation pattern of a virtual antenna radiating above a flat conducting ground plane is reproduced. The antenna and a limited surrounding space above a ground plane is folded below the ground level, resulting in a physical antenna in a ground recess that is enclosed in transformation media. The electromagnetic specification of the media surrounding the physical antenna at the bottom of the recess is provided by a properly defined coordinate transformation.
A three-step design approach is followed. First, microstrip transmission-line metamaterials for a ground-recessed probe are designed and implemented for virtual source formation above the ground plane. Transmission-line metamaterial unit cell designs for the embedding media are shown. Virtual probe formation is validated using full-wave simulations. Measured field distributions over the fabricated metamaterial-surface for an embedded probe current radiating in a ground recess confirm formation of a virtual line source above the ground plane. As a next step, resonant inclusion-based metamaterials are designed for embedding a two-dimensional electric line source in a ground recess. Metamaterials are fabricated and assembled. Measured field distributions for an effective two-dimensional configuration confirm formation of a virtual line current above the ground plane. As a final extension to a three-dimensional configuration, design, fabrication, and measurement of an embedded monopole antenna in a ground recess is presented. Poorer performance was measured compared with the two-dimensional case. The complexity and material losses associated with resonator-based, negative-index metamaterials for multiple polarizations in three-dimensional applications were identified as main technical challenges