GB1144122A - Improvements in or relating to adjustable microwave power splitters - Google Patents

Abstract

1,144,122. Directional couplers and circulators. ELECTRIC & MUSICAL INDUSTRIES Ltd. 10 March, 1966 [10 March, 1965], No. 10078/65. Heading H1W. A microwave power splitter comprises a short-slot waveguide directional coupler having an adjustable reactive impedance provided in the coupling section of the coupler whereby distribution of power between the output ports may be controlled. The impedance effects a differential phase-shift between the odd order TE 10 , and the even order TE 20 modes propagated in the coupling section. Thus, if a nominal 3 db. coupler is used and the differential phase shift is varied between + 90 and - 90 degrees, the power distribution varies between total coupling to one output port and total coupling to the other. In one embodiment, the variable impedance consists of a rod of ferrite arranged in the coupling slot parallel to the axes of the waveguides, the amount of (reciprocal) phase shift effected by the rod being determined by the magnitude and direction of an axial magnetic field. In a further embodiment, reactive elements in the form of varactor diodes are connected across the slot parallel to the direction of the electric microwave field. The embodiment shown uses ferrite elements 17, 18, 19, 20 arranged on either side of the slot 7 in regions where they are effective to shift the phase of the TE 10 mode but not the TE 20 mode. The phase shift is non-reciprocal and is controlled by opposite, reversible magnetic fields H 1 , H 2 . The device behaves as a circulator. All embodiments may be used as variable attenuators by providing one of the output ports with a dissipative terminal impedance.