Patent GB-675991-A (GB)
Title: Improvements in and relating to electron discharge high frequency apparatus
IPC: H03F3/54
Filed: 1946-05-09
Abstract: 675,991. Valve generating circuits. BRITISH THOMSON-HOUSTON CO., Ltd. (General Electric Co.). May 9, 1946, No. 14054/46. Class 40 (vi). Electron discharge high frequency apparatus comprises a cylindrical cavity resonator enclosing a substantially coaxial grid controlled electric discharge tube, such as a triode tube, having a grid connected to a metal member projecting from the envelope of the tube into the resonator, the metal member extending a considerable length from the envelope of the tube to form a boundary between the anodegrid and grid-cathode spaces in the resonator, thus constituting a wave-guide which defines between its end and the wall of the resonator a coaxial peripheral coupling opening of annular shape, and reverses the direction of propagation, thereby lengthening the path, of the wave energy travelling around the end of the metal member. In the construction shown in Fig. 1 the triode 10 is of the form described in Specification 584,787 and is surrounded by a resonator comprising a coaxial copper or brass, preferably silver-plated, cylinder 50, having a conductive well part 52 providing a mount for the base of the tube 10 and having a ring 54 provided with a ring of spring fingers 55 bearing on the metal part 18 having a high frequency capacity coupling with the cathode of the tube 10. The connection to the anode is made by a solid cylindrical conductor 59 provided with contact fingers 61, 62 engaging the anode terminals 16, 23 of the tube 10. The grid terminal 17 is peripherally connected to a long metal wave-guide forming tube 64 and through this to a terminal wire 65 extending through an insulating bead 66 in the wall of the cylinder 50 and placed at a point corresponding to a voltage node for the resonator. The effective length of the tube 64 is half a wave length. The frequency of the resonator formed by the cylinder 50 is adjusted by a plunger 71 having two sets of contact fingers 72, 73 bearing respectively on the parts 59, 50 and moved by rods 75. High-frequency energy is taken from the oscillator by a coupling loop 80 supported from a tubular conductor 82 and connected to a wire 83 forming with the conductor 82 a coaxial transmission line. In a modification the tuning plunger carries the output loop and is joined by an insulating link with a cylindrical conductive sleeve telescoped over the outer surface of the tube 64. The cylinder 50 and tube 64 may be of outwardly flared or frusto-conical shape. In the construction shown in Fig. 5, a conductive disc 128 integral with or joined to the grid 112 extends into the cylindrical resonator 117. Annular plunger tuning devices may be connected to the top and bottom faces of the cylindrical resonator. In the construction shown in Fig. 7 variable impedance means are provided by the, preferably conductive, cylinder 181 moved by the rod 184, and provided with longitudinal slots 182, 183 and having a restricted region 181<SP>1</SP> in contact with the tubular conductor 178. The cylinder 181 may be moved concurrently with the tuning plunger 185. In the construction shown in Fig. 8 the member 191 connected to the anode is insulated at 193 from the tubular conductor 192 and an annular impedance controlling member 194, in spaced relationship with conductor 192 and cylinder 176, is connected by spaced rods 195 with the tuning plunger 185. A tuned metallic cup-like member 199 provides high impedance filtering means. In the construction shown in Fig. 9 leakage of electromagnetic energy is reduced by a member 205 adjusted by the screw device 206, 207 and surrounding the members 203, 204 connected to the anode and the filtering means 208, 209. Tuning is effected by the plungers 210, 211, the plunger 210 controlling the reflected waves and permitting control of the magnitude and phase of the grid-cathode voltage. Specification 552,672 also is referred to.