Cylindrical Vector Beam Generation Using Spatially-Dispersive, Mode-Converting Metasurfaces
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The year 1972 marks the date of the first experimental demonstration of what is known today as a Cylindrical Vector Beam (CVB). Since 1972, multiple passive antennas have been proposed to generate CVBs. However, up to date there is one common downside between all the proposed passive CVBs antennas. Current passive CVBs antennas can be used to generate only standard CVBs. In this thesis, the mode converting capabilities of metasurfaces are used to design passive antennas that can generate arbitrarily defined (nonstandard) CVBs. Generating arbitrarily defined CVBs opens the door to a new class of CVBs that can be optimized for specific applications or functions.
The proposed CVB antenna consists of a mode-converting metasurface atop a coaxially-fed radial cavity. Mode-converting metasurfaces can abruptly change the amplitude and the phase profiles of incident fields, which allows for extreme control over the transmitted and reflected fields. Consequently, a mode-converting metasurface can shape the field radiated by a radial cavity at very close distances from the cavity’s aperture, or even directly at the cavity’s aperture. At the same time, a mode-converting metasurface can control the reflected fields to match a coaxial feed to the antenna, eliminating the need for additional matching circuitry.
Chair: Professor Tony Grbic