GB880372A - Improvements in or relating to waveguides - Google Patents

Abstract

880,372. Waveguide circulators. LIGNES TELEGRAPHIQUES & TELELEPHONIQUES. Dec. 8, 1959 [Jan. 19, 1959], No. 41701/59. Class 40(8). A four-port circulator comprises two parallel waveguides 1, 2 coupled by four identical directional couplers 7, 8, 9, 10 which are designed to cause complete transfer of energy from one waveguide port to another, the waveguides being loaded with a pair of non-reciprocal ferrite phase-shifters 12, 13 and a pair of dielectric member 11, 14. It can be shown that complete energy transfer is achieved if each of the couplers has a coupling factor equal to sin a where a=22¢ degrees. For propagation from left to right, the ferrite elements 12 and 13 are arranged to cause phase-shifts respectively equal to the phaseshifts caused by dielectric elements 11 and 14. Thus, input energy applied at the port 3 appears entirely at the port 6. For propagation in the opposite direction, the phaseshifts caused by the ferrite elements 12 and 13 are respectively 180 degrees greater and 180 degrees less than the phase-shifts of the corresponding dielectric elements 11 and 14. This results in a relative phase reversal of the waves combining at the couplers 9 and 7, and consequently in the total transfer of energy from port 6 to port 5. In the embodiment shown, the couplers are constituted by apertures in the common narrow wall of rectangular waveguides 1, 2. They are spaced apart by a distance greater than half a wavelength. The non-reciprocal phase-shifters 12, 13 comprise slabs of low-loss ferrite asymmetrically arranged parallel to the narrow walls of the waveguides and subject to transverse magnetic fields provided by permanent magnets 31, 32. The port 4 may be terminated by a matched resistance.