A numerical study on the influence of an input mode mixture in high-power microwave waveguide mode converters

Previous designs for waveguide mode converters generally assume a pure inpu t mode at the input. However in the actual case, the main input mode is usu ally accompanied by several spurious modes with small fractional power leve ls Based on the coupled-mode theory, this letter presents a study on the in fluence of an input mode mixture in waveguide mode converters with varying waveguide radii. A new waveguide radius perturbation form for transforming such a spurious input mode mixture simultaneously into the main output mode is also proposed in this letter. (C) 2000 John Wiley & Sons, Inc.