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A Full-Parameter, Broadband, Homogeneous, and Compact Waveguide Coupler Designed With Transformation Optics

Traditional waveguide couplers are always with large volume, nonneglectable reflection and distortion of beam profile. To provide a possible solution, some transformation optics based strategies have been proposed, however, implementation of the constitutive parameters in these strategies is very challenging. In this letter, we propose a scheme of a full-parameter, broadband, homogeneous, and compact waveguide coupler. The waveguide coupler is designed with linear homogenous coordinate transformation method and with nearly nondispersive metamaterials. Simulation results on the waveguide coupler show nearly perfect beam profile preservation and an almost total transmission in a broad band. Our strategy may find potential applications in microwave and terahertz devices.