GB1280842A - Polarization rotator - Google Patents

Abstract

1280842 Waveguide polarization rotator RCA CORPORATION 14 Aug 1969 [21 Aug 1968] 1342/72 Divided out of 1280841 Heading H1W The description is the same as in the parent Specification, but the claims relate to a phase shifter and to a polarization rotation system. As described, a phase shifter 73, Figs. 9, 10, is a square waveguide section having a ridge 86 on each of the four sides to excite a wide band of frequencies, and capable of propagating signals in both the TE 10 mode and the TE 01 mode. Spaced along two opposite corners of the waveguide section are two sets of fifteen irises 88, which cause an incoming wave with polarization parallel to a side wall of the waveguide section (e.g., in the TE 10 or TE 01 mode) to split into two equal power orthogonal components, with a nominally 90 degrees differential phase shift by the time they are propagated through the waveguide section. Posts 90 may be placed in the middle of each iris which resonate in the upper part of the operating frequency band. If the irises are arranged for resonance in the lower part of the operating frequency band, the combined impedance remains nearly constant over said band. Residual mismatch effects are compensated by tuning screws 89. A polarization rotation system uses two such phase shifters, which are coupled in axially aligned relationship, and which are relatively rotatable. TE 10 and TE 01 mode waves are converted into circularly polarized mode waves of opposite hands by passage through one phase shifter, and are re-converted into TE 10 and TE 01 mode waves by 'passage 'through the 'other phase shifter, but with an attitude which is dependent upon the angle between said phase shifters. As described, a phase shifter (75), Fig. 11 (not shown), is rotatable through gearing (111), (112) by an electric motor (110) and is coupled at each end to fixed equipment (there being a fixed phase shifter at one end) through a rotary joint. As shown in Fig. 12, a rotary joint comprises a square to circular waveguide transition 96, and a circular to square waveguide transition 97. A flange 99 is opposed by a flange 98, and is formed with grooving 100 and 101 respectively providing half-wavelength chokes at received and transmitted operating frequencies.