GB820161A - Improvements in or relating to cavity resonators - Google Patents

Abstract

820,161. Velocity modulated tubes. ELECTRIC & MUSICAL INDUSTRIES Ltd. March 12, 1956 [March 30, 1955], No. 9214/55. Class 39(1). [Also in Group XL(b)] The cavity resonator of a klystron oscillator, amplifier or similar discharge tube is tuned by a plurality of conductive plates or vanes disposed circumferentially about the resonator which can be adjusted to different angular positions. The theory of the tuning action depends on the use of the Eo mode the circular magnetic lines of force inducing a counter magnetic field in the vanes so that the magnetic and consequently the electric fields vanish in the annular region containing the vanes. The effect is as if the resonator were smaller, i.e. without the latter annular region, so that the resonant frequency is increased and is a maximum when the vanes are radial. The magnetic lines of force are as shown at 12 when the vanes are in the latter position. The plates or vanes 7 are mounted on spindles 8 at one corner thereof so that they can be individually adjusted, e.g. by a spanner acting on the square or hexagonal heads of the spindles, each spindle passing through a ceramic bush and being locked in position by a lock nut ; alternatively they may be simultaneously adjusted by providing each spindle with gear teeth 14, Fig. 3 engaged by a toothed ring operated by a worm 16. In the latter case one vane can be adjusted independently of ring 15 for fine tuning. One of the vanes can be omitted to leave space for an input or output coupling loop. The top and bottom plates of the resonator are respectively bolted and brazed to the cylindrical part. The vanes of which there may be 16 do not contact one another or the wall of the resonator. Focusing coils (not shown) surround the resonator.