Differential phase shifters using corrugated, ridge, and fin loaded waveguides

One means of converting the port conditions of a magic-tee into those of a 90° hybrid is to introduce external sections of waveguide at the symmetrical H-plane output ports having the necessary 90° phase difference. The purpose of this article is to describe a number of realizations of such differential phase shifters (DPS), including an exact synthesis procedure not requiring computer optimization. A typical design consists of a capacitively loaded waveguide for one section and an essentially inductive waveguide for the other. The latter is simply a uniform waveguide of reduced width when compared with that of the capacitive section. An example capacitive ridge DPS exhibits a maximum phase error of ±2° over a 20% bandwidth in WR75 waveguide with a return loss of better than 40 dB and an insertion loss <0.06 dB. © 2009 Wiley Periodicals, Inc.