Analysis of high power millimeter wave waveguide mode converters with input mode mixture

Based on the coupled mode theory, this paper presents the study on the infl uence of input mode mixture in circular oversized waveguide mode converters . Three kinds of commonly used waveguide mode converters, including the wav eguide mode converters with varying wall radius or small axis perturbations , and the waveguide mode converters with bent structures, are taken as the examples. The results show that the spurious input modes do not simply supe rimpose onto the output modes, and in some cases they may deteriorate the c onversion efficiency for the main output mode. Methods for transforming suc h spurious input mode mixture simultaneously into the main output mode are also presented in this paper.