GB575577A - Improvements in or relating to wave guides for the transmission of guided electromagnetic waves - Google Patents

Abstract

575,577. Wave guides. WESTERN ELECTRIC CO., Inc. March 17, 1944, No. 5046. Convention date, Nov. 3, 1942. [Classes 40 (iii) and 40 (v)] Wave guides are provided with a plurality of spaced reactance members connected across the guides and so adjusted as to produce a, desired phase shift at a particular frequency or frequency band. As shown in Fig. 1, the guide section 1 has two diametral rods 2, 3 spaced at a distance A and operating as shunt inductances. The thickness of the rods and their spacing are adjusted to give a desired phase shift and maximum transmission. A spacing of # of a wavelength provides a phase shift of 90 degrees and the addition of further similar guide sections will provide additional phase shift. Two such sections may merge into a single three-element section shown in Fig. 3 and providing 180 degrees phase shift. The central element 6 is reduced in thickness to provide half the reactance of the outer elements 5, 7. If the rods 2, 3 have gaps near their midpoints, they operate as shunt capacities and provide a phase shift of opposite sign (Fig. 4, not shown). If a wave having its electric vector at 45 degrees to the rods 2, 3 is fed into the guide, that component whose electric vector is along the line of the rods is given a phase shift of 90 degrees, whilst the component at right angles passes unchanged, thereby giving an output of circularly-polarized waves. This process is reversible. Two. aligned sections of the form shown in Fig. 1 arranged for relative rotation about their common axis, may be used as a variable phase changer, or as a means of feeding energy to a rotary radiator (Fig. 5, not shown). Another variable phase changer shown in Fig. 6 comprises two fixed 90 degrees sections 14, 15 separated by a rotatable 180 degrees section 23, the rotary joints being constituted by quarter-wave flanges 17, 24. The input wave is polarized at 45 degrees to the rods 18, 19 and is converted to a circularlypolarized wave, the direction of rotation of which is reversed by the section 23. Rotation of the section 23 varies the instantaneous orientation of the energizing wave, and the section 15 reconverts it into a linearly-polarized wave oriented at 45 degrees to the rods 20, 21, but with a change in time-phase proportional to the angle of rotation of the section 23. This phase-shift may be eliminated by providing gearing so arranged that during adjustment of the section 23, the section 15 receives twice its angular displacement (Fig. 7, not shown). In Fig. 8, a 90 degrees section 50 and a 180 degrees section 23 are interposed between a 90 degrees section 14 and an output guide 56. A crank 43 operates through gearing to rotate section 50 through twice the angle section 23 is rotated. A phase shift proportional to the angular rotation is introduced, but there is no rotation of the plane of polarization. The same result is obtained by giving the middle sections equal rotations in opposite directions and by providing a 90 degrees section instead of the plain guide 56 (Fig. 9, not shown). A 90 degrees section such as that shown in Fig. 1 may be interposed between a fixed guide fed from a coaxial line, and a fixed output guide. Rotation of the interposed section about its axis causes a wave having any desired degree of elliptic polarization to be fed to the output (Fig. 10, not shown). In Fig. 11, the input'wave is fed by a coaxial line 83, 84 to the guide 81 and the 90 degree section 50 is fixed in position with the rods 51, 52 at 45 degrees to the feed wire 84. The ellipticity of the resultant wave in the guide 81 is adjusted by sliding the piston 87. In Fig. 12, energy is switched from a main guide 89 to either of two branch guides 90, 91 set at an angle F thereto, by rotating a 180 degrees section 23. When the angles F are 120 degrees, the selective devices may be diametral rods 92, 93 terminating in coaxial stubs .95, 96. When the linearly-polarized wave fed to section 89 has its polarization rotates by section 23 until it is parallel to the rod 92, that rod acts as a reflector and the wave passes wholly into the guide 91. For intermediate positions of the section 23, the wave energy is divided between the two branches. Two input waves polarized at right angles to each other may be variably mixed by the switching device. If the angles F are other than 120 degrees, corrective shunt impedances X1, X2 are connected in the guides beyond the rods 92, 93. A junction similar to that shown in Fig. 12, but with a 90 degrees section in place of the 180 degrees section 23, may be used for switching a circularly-polarized wave into one or other of the branches according to the direction of rotation of the wave (Fig. 13, not shown).