Theoretical and Experimental Investigations of a 90° Bend Based on Nonradiative Dielectric Waveguide

Nonradiative dielectric (NRD) waveguides are recognized as suitable transmission lines for millimeter-wave applications, as they are planarized and of low loss. However, since the mode with the lowest loss is not the mode with the lowest cutoff frequency, NRD waveguides are often used in an overmoded state. Many devices based on NRD that do not need to be deformed are designed and have achieved good results. Nevertheless, the physical mechanism underpinning the bending of NRD waveguides in the direction of propagation while maintaining an unchanged cross section has not been fully elucidated, due to the inapplicability of the original coupled-wave analysis method. In this letter, we focus on a 90° NRD bend and attempt to explain the mode coupling of NRD during the bending process. The bandwidth of the designed W-band NRD bend with a transmission efficiency greater than 95% is 5 GHz.