FDTD investigation of the field distributions in rectangular hard waveguides

The authors study numerically the field distribution inside rectangular hard waveguides at the frequency at which the expected field distribution is uniform in the open region of the waveguides. The study is made by using the finite difference time domain techniques (FDTD) as described by Gwarek, Morawski and Mroczkowsk (IEEE Trans. MTT vol.41, no.2, p.311-17, 1993) and as implemented in the program V2D-Solver. The method is generally valid for arbitrary waveguide cross-sections, and is applied to rectangular waveguides with dielectrically coated E-plane walls, with strip-loaded dielectric walls, and with corrugated walls. The major interest is to see the effect of fringe fields around the metal strips and the corrugated ridges, and to study the variations of the field distribution with the strip/corrugation period and size of waveguide cross-sections. The strips are also modeled by using the asymptotic strip boundary condition. This was made possible by an extension of the V2D-Solver.