GB953177A - Improvements in or relating to electromagnetic waveguide systems - Google Patents

Abstract

953,177. Waveguide Faraday rotators. WESTERN ELECTRIC CO. Inc. Sept. 22, 1960 [Sept. 29, 1959], No. 32603/60. Heading H1W. The gyromagnetic element of a Faraday rotation device is provided with an inner core or layer of non- gyromagnetic dielectric material whereby a broad-band effect is achieved. In known rotators, using non- composite elements, the amount of rotation increases with frequency owing to the concentration of the guided wave energy towards the centre of the element. Replacement of the centre of the element with non-gyromagnetic material increases the range over which rotation is acceptably constant. The composite element of Fig. 3 comprises a tube 12 of a suitable gyromagnetic material, e.g. a ferrite, surrounding a core 13, the ratio of the radii r, R being less than 2 and the dielectric constants of the two materials being preferably equal. The element is aligned on the axis of a round wave 10 and is longitudinally polarized either by permanent magnetization or by external means. The dielectric core is extended at its ends to form tapered impedance-matching terminations. The element 40 of Fig. 4 comprises layers 41, 42 of gyromagnetic material arranged on either side of a composite dielectric slab 43, 44. The two parts of the slab are separated by a layer 52 of lossy material whereby a degree of attenuation dependent upon the angle between the polarization and the layer is produced. The slabs 41, 42 may be permanently magnetized or the element may be surrounded by a solenoid. The wedge-shaped ends 45, 46 of the element are supported by dielectric members 10, 51 within the ends of input and output waveguides 48, 49.