Novel metasurface technologies for coupling mitigation in antenna arrays

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The focus of this proposal is an enclosed wideband dipole array manufactured by Sinclair Technologies (Aurora, ON), which contains four dipole antennas operating over a frequency band from 746MHz to 960MHz. The array is arranged along a single axis and the constituent dipoles are separated by large centre-to-centre distances that result in an unfortunate design trade-off: whereas compactness is desired, close spacing of the antenna-array elements results in a phenomenon known as mutual coupling that compromises the gain of the antenna array; conversely, maximizing the spacing to mitigate mutual coupling results in an inordinately large antenna structure. As a result, current designs sacrifice some gain in favour of compactness. The marketability of these antennas is strongly dependent on their size, weight, cost, and gain performance, and it is therefore important to devise strategies to either minimize their size without compromising their gain performance or, equivalently, improve their gains for a given size. The proposed research focuses on the second approach, and attempts to reduce deleterious mutual coupling facilitated through sidelobes in the antennas' radiation patterns through the use of electromagnetic 'metasurfaces' (MTSs). MTSs are two-dimensional periodic structures engineered to interact with electromagnetic waves (such as those radiated by antennas) in unique ways resulting in phenomena that are either impossible or difficult to achieve using natural materials. Recently, the research group of Prof. Ashwin Iyer at the University of Alberta (Edmonton, AB) has developed a MTS technology consisting of a periodic arrangement of specially designed apertures possessing properties that allow the MTS to selectively transmit or reflect signals, a property that may be exploited to isolate antennas in an array environment simply by placing one or several MTSs between them.