Low-loss flexible dielectric waveguide for millimeter-wave transmission and its application to devices

A finite-difference method has been developed for computing the propagation constants and field distributions for dielectric waveguides of arbitrary cross section and dielectric constant. The results of the method are compared with the exact solution for a round waveguide. Additional calculations are made for rectangular waveguides and the results compared with Marcatili's approximate solutions. Results are given for a dielectric waveguide phase shifter using a LiNbO3 waveguide. Approximately one radian of phase shift at 94 GHz was obtained with 1000 V peak audio frequency voltage applied to electrodes on the LiNbO3 waveguide. Amplitude modulation of 70% was observed in a microwave bridge configuration, in good agreement with theory. Other uses of nonlinear/electro-optic materials in the millimeter wave range are discussed, including electronically-scanned antennas and electronically-tuned filters.