State of the waveguide art

The use of overmoded waveguides in microwave communications is discussed. The principal applications of this technology and its loss advantages are reviewed, and the primary problem, the transition from single-moded to overmoded waveguide, is addressed. Reasons for choosing between circular and rectangular waveguide systems for overmoded applications are considered, and the importance of perfect cylindrical geometry is emphasized. The use of overmoded TE(11) circular waveguide systems is briefly discussed. Appropriate design for the transition from higher to lower modes, and from rectangular to circular waveguides, is covered, as are mode suppressor designs, circular electric mode operation, bends, and the overmoded rectangular waveguide.