GB646009A - Improvements in or relating to electrical oscillation generators - Google Patents

Abstract

646,009. Magnetrons. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. May 20, 1946, No. 15262. Convention date, Nov. 16, 1944. [Class 39 (i)] Variable-frequency high-frequency apparatus comprises a cavity resonator 11, Fig. I, situated in a magnetostatic field H whose magnetic lines of force extend through the resonator in one direction, auxiliary means (such as a cavity magnetron 27) for exciting the resonator to produce a high-frequency electric field E extending in planes normal to H, means (such as cathode 14) for directing a beam of electrons into and through the resonator in a direction substantially parallel to H, and means for variably controlling the transit time or intensity of the beam. It is shown that, if the frequency is in the region of the Larmor frequency eH/m, a very small change of transit time (by a signal from transformer 25 which varies the beam accelerating voltage) will introduce a reactive impedance into the resonator 11, either capacitative or inductive, and this will result in a change in frequency of the magnetron 27. A change in beam density (by a signal from transformer 20 applied to control grid 15) will produce a similar effect by altering the value of the reactive impedance. Electrode 16 may collect the beam or reflect it back to the resonator 11. In a modification, the beam is introduced into one or more of the cavity resonators of the magnetron itself, by means of auxiliary cathodes 66, Fig. 9, the magnetic field used being the main field between magnetic inserts 34, 35. Insert 34 carries the main cathode and insert 35 the auxiliary cathodes, both being supported from the anode block 30 by spacers 36, 37, 40, 41. Control grids 66<SP>1</SP> are situated in front of each cathode 66. Collectors 67 are supported direct from the header 45. An annular auxiliary cathode and control grid could be used.