GB672639A - Improvements in or relating to systems for amplifying, generating or otherwise operating upon oscillations of very high frequency and to electron-discharge tubes for use therein - Google Patents

Abstract

672,639. Thermionic valves, magnetrons. PHILIPS LAMPS, Ltd. Oct. 22, 1946 [March 1, 1943; Sept. 3, 1943], Nos. 31372/46. and 31373/46. Class 39 (i). An electron discharge tube for amplifying or generating very high frequency oscillations, comprises a pair of parallel electrodes constituting opposite walls of a hollow wave-guide, not greater than a half wavelength long if the waveguide is closed, and not greater than a quarter wavelength long if it is open ended; the cathode constitutes one of, or is parallel to, the parallel electrodes, is coextensive with them, and is emissive over its whole surface. The relatively large cathode enables high powers to be obtained. Fig. 1 shows the application to a triode where wave-guides are constituted by the cathode 6 and the control grid 5, and by the control grid 5 and the anode 4. The input and output of the oscillatory voltages may be effected through Lecher lines 1, 3, or through hollow wave-guides or coaxial lines. The input and output points may be located so as to produce any desired difference of phase. The invention is applicable to braking-field or frequency - changing systems, and to diodes, tetrodes or pentodes. As applied to a magnetron, a two-electrode system is rolled up to form a septate coaxial wave-guide 4, 6, Fig. '4. The electrode 6 may be an accelerating grid and made of gauze, the cathode consisting of a number of circularly distributed filaments, or of a coiled filament, inside the electrode 6. The septum 9 may be constituted by a number of spokes. Preferably the electron transit-time is so adjusted that H01-type oscillations are produced. The Specification as open to inspection under Sect. 91 comprises also a triode with coaxial electrodes. This subject-matter does not appear in the Specification as accepted.