GB1046285A - Improvements in coupling devices for radio-electrical circuits - Google Patents

Abstract

1,046,285. Tuning cavity resonators. COMPAGNIE FRANCAIS THOMSON-HOUSTON. April 2, 1964 [April 2, 1963], No. 13720/64. Heading H1W. An output coupling for a cavity resonator comprises a conductor arranged within the cavity between an output terminal and an end wall, the conductor passing through a tuning piston and providing a variable output loop, whereby a constant bandwidth is preserved as the cavity is tuned over a wide range of frequencies. As shown, the internal and external conductors 8, 4 of a coaxial cavity are respectively connected to the grid 6 and anode 3 of a tube 1. A flat conductive strip 15 lies halfway between the conductors and extends from the central conductor 19 of a coaxial output socket 20 to an adjustable securing bracket 16. The strip may be made of conductive material or of an insulator coated with e.g. silver. The length of the active part 9 of the cavity and the length of the coupling loop formed by the strip are both varied by a piston 10 carrying resilient contacts which bear upon one or both sides of the strip. Constant bandwidth is obtained by adjusting the values of (a) the width of the strip, (b) the position of the strip between the conductors, (c) the axial position of the output socket. Two strips forming a parallel line may be used. The piston may be capacitatively connected to the strip and the strip or the coating of metal on it may be shaped to provide a capacitor electrode having an area which varies with the position of the piston.