Bandwidth studies of TE/sub 0n/-TE/sub 0(n+1)/ ripple-wall mode converters in circular waveguide

This paper presents the design, numerical analysis, and testing of several symmetric periodic mode converters of two generic types: a uniform ripple-wall converter and a nonuniform ripple-wall converter. All designs operate at a central frequency of 17.136 GHz and convert circular electric modes (TE/sub 0n/) from one radial mode to the next higher mode. The emphasis of the design study is to maximize the bandwidth of the device without sacrificing mode purity. Mode converters from the TE/sub 01/ to TE/sub 02/ mode and from the TE/sub 02/ to TE/sub 03/ mode were investigated in depth, and two designs, each with six periods, were constructed and tested. The nonuniform ripple seems to have a significant advantage over the constant ripple design for the higher mode converter, while the designs for the lower mode converter are comparable. Experimental measurements agree well with the theoretical results both in terms of bandwidth and mode content.