Metasurface enhanced ultra-wideband multifunctional antenna arrays and Fabry-Perot antennas

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In recent years, the demand for ultra-wideband (UWB) antennas and arrays has escalated due to their flexibility and high data rate capabilities. This demand is driven by bandwidth intensive applications such as radio telescopes, satellite communications, and advanced radar systems. Wideband antennas enable the incorporation of multiple steerable beams, polarizations, and frequency bands onto a single multifunctional aperture. Two of the main obstacles to truly multifunctional tightly coupled antenna arrays (TCAAs) is the problem of impedance mismatch at the aperture–air boundary and the need for a wideband and fully integrated feed network. The high cost and losses in the feed networks of TCAAs renders them impractical for some applications. In these cases, the low-cost and highly efficient Fabry-Perot antenna (FPA) provides a possible solution. In the first part of this thesis, we present the design, analysis, and practical implementation of a 10x10 wideband TCAA with a very high figure of merit. The array figure of merit is a single number which takes into account the bandwidth, profile, polarization, scan range, and overall complexity of the array. An improved design of the fabricated array has a performance that approaches the fundamental limits of low profile arrays with a bandwidth of 5.5:1, a maximum scan range of 80° along the E-plane, and a profile of ~λL/12. This excellent performance is enabled by a newly introduced feed network that is simple, inexpensive, and extremely wideband; in conjunction with a novel ultra-thin metasurface superstrate for wideband wide angle impedance matching. The usual method of enhancing the gain bandwidth of FPAs involve the use of multi-layered superstrate structures which increase their profile and complexity. In the second part of this thesis, we develop a new approach to FPA gain bandwidth enhancement. Using this new approach, a small foot print, wideband, and low-profile FPA empowered by a single multi-resonant metasurface superstrate is designed, fabricated and tested. Due to the small foot print of this FPA, it can be easily employed as an element in an active array setting without the introduction of grating lobes. At the same time, the number of active elements will be significantly reduced compared to the dense TCAAs leading to substantial cost reductions.
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