GB851519A - Electromagnetic wave transmission device - Google Patents

Abstract

851,519. Waveguide ferrite devices. HUGHES AIRCRAFT CO. Dec. 11, 1958 [Jan. 3, 1958], No. 40049/58. Class 40(8). [Also in Group XL(c)] An electromagnetic wave transmission device, suitable for use as a microwave modulator or switch, comprising a ferrite element located inside a waveguide and inside a solenoid, is characterized in that said device has a body of dielectric material in which a bore is coated with a metallic film providing said waveguide, and that said solenoid is disposed inside said waveguide. The device shown comprises a dielectric cylinder 10, e.g. of nylon, having a bore 12 on which a conductive film e.g. of silver, nickel, copper or gold is deposited by vaporization, precipitation or chemical reduction plating to form a waveguide 16. The thickness of the film is made approximately four times the skin depth of the metal at the fundamental frequency of the microwaves to be modulated so the device has a low insertion loss. A ferrite element 18, having at each end a tapered portion surrounded by a dielectric plug 34, is supported in an axial bore of a coil former 20 of dielectric material having a reduced diameter section 22 containing a solenoid 26 connected by leads 28 and 30 to a modulating signal source 32. The coil former 20 is surrounded by a dielectric sleeve 24. Resistive cards 44 and 46 are located between four semi-cylindrical supports 48 of dielectric material similar to that of the coil former 20 and the sleeve 24. Metallic plates 36 and 38 fastened to the ends of the cylinder 10 have rectangular openings 40 and 42 with their longer dimension parallel to the cards 44 and 46. Auxiliary solenoids 52 may be accommodated in reduced diameter sections 50 in the surface of the cylinder 10. In operation, HO1 mode waves from a source 54 excite H11 waves in the waveguide 16. If the E vector is perpendicular to the card 44 no energy is absorbed. After rotation by the ferrite element 18 components parallel to the card 46 are absorbed and components perpendicular thereto are transmitted to a utilization device 56 in the form of an amplitude modulated signal. Placing the solenoid 26 inside the waveguide 16 reduces eddy current losses and provides a low reluctance magnetic circuit, thus enabling the source 32 to be of low power and to operate at modulating frequencies of many mcs./sec.