IEEE TAP Paper Published (03-Feb-2022)

Our paper on metagrating-inspired solutions for suppressing reflections in waveguide bends, written by Liran Biniashvili and Ariel Epstein, has been published in the IEEE Transactions on Antennas and Propagation. The paper derives a semianlaytical methodology to devise locations for subwavelength scatterers that would eliminate spurious scattering in rectangular waveguide discontinuities by producing secondary fields that destructively interfere with the unwanted reflections in the input port. The analytical model requires modal expansions in the straight waveguide sections (rectangular waveguide modes) as well as in the junction (treated as a radial waveguide section), allowing efficient and accurate retrieval of scattering coefficients without requiring numerical solvers. Including a small scatterer in the junction is performed by incorporating the suitable Green’s function, allowing for calculation of the potential spots as well as the required induced current for mitigation of back reflections while retaining passivity – similar to what has been achieved for metagratings for free space beam manipulation. The examination of these perfect transmission locations reveal fundamental insights regarding the scattering processes within the junction, manifested in the formation of symmetric and antisymmetric solution branches. The work is completed by deriving approximated analytical formulas for the radius of a metallic cylindrical post that can implement the subwavelength scatterer in practice, showing good performance also in terms of bandwidth and sensitivity to fabrication inaccuracies. The work introduces a simple, effective, and semianalytically designed solution for seamless waveguide bends, while demonstrating the versatility of the metagrating concept, beyond beam manipulation.