Characteristic impedance of nonradiative dielectric waveguide and its application

In this paper a formula for determining the characteristic impedance of the nonradiative dielectric waveguide (NRD-guide) is presented. The numerical results are obtained, which are very useful for designing NRD waveguide components, such as impedance transformers, filters, branch-line hybrids, and active circuits. As a practical example for applying the formula, a 3 dB brainched NRD-guide directional coupler was designed and fabricated. The experiments show good consistency with the theory.