Tunable Gradient-Index Fishnet for Beam Steering Applications at 60 GHz
Final Report Abstract
Metamaterials possess electrical and magnetic responses to free-space wave excitation that are not found in any naturally occurring material. In this work, so-called fishnet metamaterials were investigated, which allow a wide range of possible amplitude and phase responses. In the application as gradient index lens, they can be used for static beam shaping. Due to their planar structure with a thickness below one wavelength, they have a lower weight compared to similarly designed Fresnel lenses and manufacturing is performed using established PCB processes. By introducing a tunable substrate into the unit cell, realized here by liquid crystal (LC), the fishnet structure can be used for reconfigurable beamforming. This is done by applying a bias voltage to each unit cell, which locally adjusts the transmission properties, especially the phase, of the overall array. Challenging aspects are the fabrication of the liquid crystal cavities, the design of a unit cell that allows individual control of each unit cell in a fully populated two-dimensional array and the circumvention of the limitation in phase tunability of existing fishnet designs. Therefore, in this work, fabrication techniques were first applied that allow the realization of a fishnet metamaterial on alumina at 60 GHz and fused-silica glass at 132 GHz. The problem of individual driving of the unit cells was solved by means of a matrix method, which is similar to the driving method of passive LC displays. Furthermore, concepts that significantly change the fishnet structure were investigated, with the goal of achieving complete 360° phase tunability, as required for an ideal Fresnel lens.
Publications
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Liquid Crystal Based Tunable Reflection-Type Power Divider. 2018 48th European Microwave Conference (EuMC), 45-48. IEEE.
Nickel, Matthias; Muh, Mario; Reese, Roland; Polat, Ersin; Jost, Matthias; Damm, Christian; Jakoby, Rolf & Maune, Holger
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A Millimeter-Wave Beam-Steering Lens Antenna With Reconfigurable Aperture Using Liquid Crystal. IEEE Transactions on Antennas and Propagation, 67(8), 5313-5324.
Reese, Roland; Jost, Matthias; Polat, Ersin; Tesmer, Henning; Strobl, Jonathan; Schuster, Christian; Nickel, Matthias; Jakoby, Rolf & Maune, Holger
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"Model-based Optimization of Fishnet Metamaterial Lenses under Oblique Incidence," 2022 14th German Microwave Conference (GeMiC), Ulm, Germany, 2022, pp. 01-04
A. Diepolder, M. Mueh, S. Brandl, C. Waldschmidt & C. Damm
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Characterization Techniques for Reconfigurable Reflectarray Unit Cells at 240 GHz. IEEE Antennas and Wireless Propagation Letters, 21(9), 1911-1915.
Brandl, Susanne; Mueh, Mario; Diepolder, Adrian; Kunakovskaya, Ekaterina; Ulusoy, A. Cagr; Damm, Christian & Waldschmidt, Christian
