GB581481A - Improvements in or relating to thermionic devices for use with dielectric wave guides - Google Patents

Abstract

581,481. Electron oscillators ; wave guides. STANDARD TELEPHONES & CABLES, Ltd., and TOMLIN, S. G. Aug. 29, 1941, No. 11078. [Classes 39 (i) and 40 (v)] Electron discharge apparatus for generating electromagnetic waves in a dielectric guide 1 having a portion with one end closed, as by a piston P, and the other end adapted for passage of the waves, as through apertured diaphragm D to sectoral horn M, comprises means for generating and projecting an original beam of electrons across the portion at a field antinode and in a direction parallel to the electric field, and means for deriving from the original beam a second electron beam adapted to be projected across the portion of the guide in the opposite direction. The beam from cathode K and grid G is velocity modulated in the gap 0 marked off by fins F extending into the guide towards aperture Q. On arriving at the final electrode A, the beam may (a) be entirely repelled so that the now bunched stream repasses the gap 0 in time to deliver up energy to the guide, (b) be separated into fast electrons which are collected and slow electrons which return to deliver energy to the guide, or (c) strike the electrode A at a velocity sufficient to generate a bunched stream of secondary electrons, which returns to deliver energy to the guide. In case (b) the transit time from O to A and back is n+¢ periods ; in case (c) it may be n periods. In a modification, a metal septum M, Fig. 2A, extends horizontally across the centre of the guide and supports the fins T between two gaps O1, O2. In the H10 type wave used the equipotential lines are horizontal so that the septum does not disturb the wave. The electric field is in the same direction at both gaps so that if the beam is to be velocity modulated at O1 and deliver energy at 02, the transit time should be n-“ periods. By adjusting the potential of electrode A or of a grid placed before it so as to work on a curved characteristic, the device may function as a rectifier, while at the same time the repelled electrons returning to the guide produce regeneration. By tuning the guide to a wave length slightly different from that falling upon the horn M, a rectified output at the difference frequency is obtained. In a modification, two guides are traversed in succession by the same beam, the first receiving the incoming wave and the second producing the local oscillation and rectifying the resultant mixed frequency. The wave-guides may be circular and may have an axial conductor. If the E11 or E10 modes are used, the fins F or T may be dispensed with, as the field in the centre is small. A formula is given for the best relation between breadth and thickness of a rectangular guide for a given wave-length. The guides may be tuned by compressing the sides. Where there are several antinodes a separate beam may traverse the guide at each of them. A magnet NS concentrates the beam.