Efficient energy transfer through a bifilar metamaterial line connecting microwave waveguides

Microwave waveguides allow an effective transfer of electromagnetic energy through straight connection or well-rounded curves, but become rather inefficient in case of sharp bends or squeezed waveguide cross-sections. Here, we discuss the possibility to funnel the electromagnetic energy propagating in a waveguide through arbitrarily curved narrow channels hosting a metamaterial-inspired structure able to convert the propagating mode of the waveguide in an electric signal, and vice versa. We show experimentally how sharp bends can be inserted within these propagation channels of arbitrary lengths without introducing significant insertion losses. In particular, efficient energy funneling in 90°-, 180°-, and “S”-shaped bends are numerically and experimentally verified. The proposed reflectionless waveguide bends may find applications in modern radar and antenna systems, where the demand for space and weight reduction of the electromagnetic circuitry is ever growing.