Application of the scattering optimization method for the design of circular waveguide mode converters

Design and fabrication of compact mode converters has been of interest since the development of high power gyrotrons for plasma heating. Haq et al. (1994, 1995) have introduced the scattering optimization method for the design of these mode converters. Unlike the coupled mode theory approach, this method relies on sharp discontinuities in the waveguide to achieve mode conversion in shorter lengths. The approach was initially demonstrated for the simple structure of parallel plate waveguides. Numerical simulations indicated that the designed mode converters could achieve very high efficiency with lengths much smaller than the conventional designs. This paper gives some results related to the design of mode converters in circular waveguides and suggests improvements in the scattering optimization design procedure.