A broad-band waveguide junction containing dielectric

A method is described for obtaining a broad-band impedance match between two joined waveguides of differing cross-section. The method involves the use of an axially mounted dielectric which partially fills the waveguide cross-section. With an appropriate choice of dielectric cross-sectional area and permittivity the electromagnetic field is mainly confined to the region of the rod. Under these conditions the waveguide cross-section may be abruptly changed without appreciable reflection. The case of two joined circular waveguides containing an axial dielectric rod is treated theoretically for H01-mode propagation. A similar configuration is studied experimentally for the H11-type mode of propagation. In both cases an appreciable reduction in reflection coefficient is demonstrated when the rod is present. The application of the principle to other waveguide crosssections is briefly mentioned.