GB806683A - Improvements in or relating to electronic devices - Google Patents

Abstract

806,683. Coaxial line terminations. ELLIOTT BROS. (LONDON) Ltd. Dec. 12, 1956 [Dec. 12, 1955], No. 35668/55. Class 40 (8). [Also in Group XL (a)] A discharge tube adapted to be inserted into a waveguide to extract energy therefrom comprises a cathode arranged axially of a cylindrical anode to provide a coaxial transmission line, the cathode extending beyond at least one end of the anode, a transformer associated with said cathode extension adapted to transform the mode of the energy propagated through the waveguide to a mode for propagation along the anode-cathode line, and a body of lossy dielectric material surrounding the cathode at a location spaced from the transformer in the direction of energy propagation. In Fig. 1, the discharge tube is an elongated tubular glass envelope 3a, 3b which may contain gas at low pressure. The anode 2 is supported by a sleeve 4 having an annular flange 5 extending through the envelope to form an external connection. The flange 5 is flexible so as to accommodate axial expansion. The cathode 1 is a hollow tube extending beyond the anode at both ends. At one end it is connected to a transformer 6. At the other end it is supported by a spider 7, and connected via a spring 11 to a contact-pin 13 extending through the end of the envelope, the pin being soldered to a disc 17. A hollow metal sleeve 15 of frusto-conical form is slipped over this end of the tube, its narrower end being coplanar with the end of the anode 2. Cooling fins 18 may be attached to the sleeve. The space between sleeve and tube is filled with a lossy material 16 such as a suspension of ferromagnetic (e.g. carbonyl-iron) dust in a resinous binding medium. The energy propagated along the anode-cathode line is gradually absorbed by the lossy material, with minimal reflection. The dimensions are such that when the tube is inserted into the rectangular waveguide 29, one end of the anode sleeve is level with one wall of the waveguide while the transformer 6 extends through the other wall. A choke block 28 surrounds the junction of the tube with the waveguide. The tube is secured to the choke block by means of a threaded nut 25 which engages with a threaded member 27 forming part of the block. The disc 5 and a contacting metal ring 41 are clamped between insulating washers 24, 40. The ring 41 is connected via a lead 42 and pin 43 to a plug 31 for connection to a coaxial cable, which thus takes the anode potential to a suitable indicating device. The lossy material may be within the envelope instead of outside it, and Figs. 3-8 (not shown), illustrate different forms of distribution and arrangement.