Double dielectric-slab-filled waveguide phase shifter

A field theory method based on the orthogonal expansion into eigenmodes is presented for the design of double dielectric-slab-filled waveguide phase shifters with linerly tapered sections. Prototypes of 90 deg differential phase shift with reference to a corresponding empty waveguide of the same length achieved typically about + or - 4-deg phase error and less than -30-dB input reflection within + or - 5-percent bandwidth, for WR 102-band (7-11 GHz) through WR 28-band (26.5-40 GHz) waveguides. Design curves for differential phase shifts of 12.25 deg, 22.5 deg, 45 deg, 90 deg, 180 deg, and 270 deg are given. Utilizing the differential phase-compensation effect of the dispersive behavior of the dielectric-filled and empty reference waveguides, the phase error is only + or - 1 deg within + or - 8.5-percent bandwidth. Further investigations include composite phase shifters, mechanical lateral displacement, and tolerance influences. An experimental 90-deg phase shifter for 14-GHz midband frequency shows good agreement between theory and measurements.