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Design of Tensor Impedance Transmitarrays For Polarization Control

Tensor impedance transmitarrays consist of layers of tensor impedance surfaces, separated by dielectric spacers. Because the surface impedance of each layer is a tensor, an arbitrarily polarized incident field is scattered into its constituent TE and TM components. This gives rise to transmitarrays capable of altering the polarization state of an incident field. Various tensor impedance transmitarray have been proposed in the literature to alter the polarization, however no comprehensive methodology has been proposed to design these structures. In this work we propose a procedure for designing tensor impedance transmitarrays using multi-conductor transmissionline (MTL) theory. We treat the transmitarray by modelling free-space and the dielectric spacers as an MTL supporting TE and TM modes with each tensor impedance surface as a shunt load along the MTL. By using simple MTL concepts we can design a transmitarray to be reflectionless while controlling the transmission through the layers and thus the transmitted polarization state. We demonstrate this procedure for two classes of tensor impedance transmitarrays while also validating the design using full-wave simulation. The first class are symmetric transmitarrays which can alter a given incident polarization state into a desired polarization state. The second class are asymmetric transmitarrays which can also implement chiral polarization effects such as a linear polarization rotation and a circular polarization selectivity.