Patent GB-560982-A (GB)
Title: Improvements in or relating to generators of ultra-short electromagnetic waves
IPC: H01J25/30
Filed: 1939-10-16
Abstract: 560,982. Electron oscillators. WALTON, G. W. Oct. 16, 1939, Nos. 27995 and 30567. [Classes 39 (i) and 40 (v)] In a generator amplifier or detector of ultra high-frequency oscillations, two or more of the electrodes are resonator antennµ which are set apart at such distances that standing waves flow between the electrodes, thereby causing density modulations of the electrons, which sustain the oscillations in the antennµ. The electrodes cathode 1, grid 4 and anode 6, Fig. IC, are half wavelength long with central nodes; the cathode is quarter wave or any odd multiple thereof from the grid which is half wave-length or multiples thereof from the anode. The cathode is at the node of the standing waves and the other electrodes at the widest part of the loops ; departures of the spacings alters the total reflection at the cathode. The oscillations generated in the antennµ with the standing waves cause density modulation of the electron flow in three dimensions. To increase the power output, numbers of harmonic resonators are used together ; a simple harmonic resonator oscillating at the 19th harmonic of the fundamental may be used with three nodes 1, 2, 3, Fig. 2A. Numbers of such resonators may be used with the nodes connected forming a grid'structure as shown in Fig. 2B ; this may be made cylindrical or prismatic. In a modification, alternate segments of the resonator are at right angles, the vertical segments 1, 2, Fig. 2C, resonating while the substantially horizontal segments 5, 6 neutralize each other ; but by a parallel arrangement radiation in the plane of the figure could be obtained. In a further arrangement, Fig. 2D (not shown), the resonators and their nodal connections give the appearance of a brick course. The resonators may be formed by perforating a metal sheet. In any structure, an electrode may be in part constructed as shown in Fig. 2B and part as in Fig. 2C. In a generator, a grid between a cathode 1, Fig. 4, and anode 3 consists of three resonators 2, 4, 5, the outer resonators 2, 5 being connected together and set at opposite phase to the central resonator 4 ; the cathode 1 need not be a resonator, a virtual cathode being formed by a positively biassed electrode 7. A standing wave will be formed with the electrode 7 at the node. Oscillation on a definite wave-length will be difficult to obtain owing to errors in manufacture ; controlled band operation is obtained with an accelerating electrode as 7, Fig. 4 ; this will be concentric with the cathode, the other electrodes being arranged eccentrically and all three having the ends inclined. A detector may comprise only a resonant cathode and anode or the cathode and anode 1, 4, Fig. 8, are not resonators, an accelerator 2 and a negatively biassed control grid 3 being the detector elements and acting as resonators ; the anode and cathode are shorter than the other electrodes, the grid 3 being set in oscillation by the received waves. Combined with an ordinary control grid 5 this may be used in aircraft detection, local signals being applied to this grid 5 to give the code letters of the plane, which will not be radiated until the correct wave-length is applied to the control 3. Valves as shown in Fig. 8 may be used in cascade or such a valve may be combined in one envelope with an amplifier, the grid 3 being directly connected to the control grid of the amplifier stage, which has an accelerator connected to the accelerator 2. In a modified form, an electron " disc " is obtained by passing the electrons between cylindrical electrodes 2, Fig. 10A, with negative bias and accelerator electrodes 4 of ring form ; the resonator electrodes are formed by the anode 6 and divided control electrode 5. An ordinary signal electrode 3 is provided ; a number of such " disc " arrangements may be used with harmonic resonators. The upper and lower parts of the control electrodes are crossconnected.