GB793164A - Improvements in or relating to non-reciprocal electromagnetic transmission systems - Google Patents

Abstract

793,164. Non-reciprocal waveguide transmission systems. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Nov. 16, 1955 [Nov. 19, 1954], No. 32787/55. Class 40 (8). A non-reciprocal transmission arrangement comprises a strip of highfrequency ferromagnetic material, e.g. ferrite, arranged in a waveguide at a point where the magnetic vector is circularly polarized, the strip being magnetically polarized in a plane normal to the plane o f rotation of the vector to a degree sufficient to produce ferromagnetic resonance at the working frequency. To improve the impedance-matching of the strip it is provided on one side with a layer of dielectric material the dielectric constant of which is equal to the square root of the dielectric constant of the ferrite material and the thickness of which is equal to of the wavelength in the dielectric. For a rectangular guide 1 propagating in the H01 mode the ferrite strip 2, provided with matching dielectric layer 3, is situated at a point defined by: (p is the propagation constant), where the Hx and Hz components of the high-frequency magnetic field being equal and in quadrature combine to produce a vector of constant magnitude rotating in a sense determined by the direction of propagation. If the sense of rotation is the same as that of the electron-spin precession produced by the polarizing field Ho absorption of the electromagnetic wave results. For the opposite sense of rotation, corresponding to the opposite direction of propagation, absorption is negligible. The invention may be applied to circular guides in which for Ho modes of propagation a circularly polarized field exists at two different radial distances from the axis. A ferrite cylinder having a radius equal to either of these distances is axially arranged in the guide and is circumferentially polarized by means of a D.C. conductor situated along the axis. The matching dielectric layer is arranged inside or outside the ferrite cylinder according to whether the radius of the latter has the greater or less of the two alternative values. The dielectric may be quartz glass.