Patent GB-843616-A (GB)
Title: Electromagnetic wave conductors
IPC: H01P1/365
Filed: 1957-06-27
Abstract: 843,616. Non-reciprocal microwave networks. SPERRY RAND CORPORATION. June 27, 1957 [July 12, 1956], No. 20358/57. Class 40(8). In order to produce the circularlypolarized magnetic field component necessary for non-reciprocal wave attenuation in a ferrite-loaded transmission line, the space between the two conductors of the line is filled with two materials having different permittivities and having a common boundary extending in the direction of wave propagation. In the constructions described one of the dielectric materials is air and the other a solid which may be in the form of two elongated elements 33, 34 extending between the conductors 11, 12 of a coaxial transmission line. The presence of the elements causes perturbation of the e-m field and produces a rotating magnetic field component at the positions occupied by two elongated ferrite rods 40, 41. A steady magnetic field H B  applied at right angles to the direction of propagation is adjusted to such a value that the ferrite element produces little or no effect on waves propagated in the forward direction but exhibits gyromagnetic resonance for waves travelling in the reverse direction whereby these waves are absorbed. Alternatively, the direction of the field H B  is reversed and adjusted so that the ferrite exhibits zero effective permeability to the forward wave which is propagated without loss in the space surrounding the rods. The reverse wave encounters a finite permeability in the rods which are made lossy to cause attenuation of this wave. In a modification of this construction, the solid dielectric occupies a 180 degree sector of the annular space between the conductors. In a further modification (Fig. 9, not shown), a second pair of ferrite rods is arranged on the surfaces 36, 38 opposite the rods 40, 41. Both pairs of rods are subject to the same polarizing magnetic field but are made of ferrites having different characteristics whereby, whilst the first pair of rods eliminate the reverse wave by gyromagnetic resonance, the second pair operate under near-resonant conditions and attenuate the forward wave by a desired amount. The first pair of rods has no effect on the forward wave and the second pair no effect on the reverse wave. In another modification (Fig. 12, not shown) broad band operation is achieved by using a number of elements of different permittivities arranged in tandem. Since ferrite is itself a dielectric material, the dielectric elements may be replaced in the various constructions by ferrite, in which case the ferrite rods may be eliminated. In the case of a two-conductor strip line, ferrite elements 53, 54, Fig. 10, are positioned on the surface of the solid dielectric layer 52 separating conductors 50, 51. In the double strip line of Fig. 11 ferrite elements 66, 67 are positioned on either side of central conductor 60. In order to obtain a circularly-polarized field, the dielectric member 63 fills only part of the space between outer conductors 61, 62. Specification 836,440 is referred to. Reference has been directed by the Comptroller to Specification 800,892.