A Compact and Broadband 90-Degree Waveguide Twist Transformer for Integrated Waveguide Subsystems

A novel 90-degree waveguide twist is presented. The design features compactness by utilizing a central triple-mode quarter-wave transformer region between input and output waveguides of different cross sections. Return-loss values in excess of 30 dB are obtained over an operating bandwidth close to 20 percent. Larger bandwidths are obtained by using additional quarter-wave steps preceding and/or succeeding the central transformer region. Several different design examples at 4, 6, 19 and 26 GHz are presented for this unique 90-degree twist transformer approach. Experimental verification is provided in the 6 and 19 GHz range.