Analysis and Performance of Waveguide-Hybrid Rings for Microwaves

TN A recent paper 1 , Mr. W. A. Tyrrell has described two general types of waveguide or waveguide/coaxial structures whose properties include bridge or null balance characteristics analogous to those of the hybrid coil common in voice-frequency communication practice. One type, the hybrid junction, is a particular orthogonal junction of four rectangular waveguides. Certain properties of the hybrid junction, notably its impedance characteristics, have been the subject of a British publication 2 . The present paper presents a method for detailed analysis of the other general structure described by Tyrrell, the hybrid ring. This latter structure is essentially an annular ring or annulus of waveguide, at present usually an integral number of quarter wavelengths in circumference, and fitted with an appropriate number of series or shunt branch taps. In this article, phrases such as "quarter wavelength," etc., describing t a p spacing or mean annulus perimeter, refer to wavelength in the guide, not to free space wavelength. The method of analysis employed herein is essentially to treat the tapped annulus as a re-entrant transmission line. Certain circuit equivalences and quarter wave impedance transformations were used by Tyrrell in his paper to develop, with the aid of the reciprocity theorem, many basic properties of hybrid circles and hybrid junctions. In the present paper " T " or "lattice" equivalents (neglecting dissipation) are developed for each section of the annulus, and the method of determinants is applied.