GB668162A - Improvements in or relating to amplifiers incorporating electron discharge devices for centimetre-wavelengths - Google Patents

Abstract

668,162. Travelling-wave tubes. PHILIPS ELECTRICAL, Ltd. Jan. 9, 1948 [Jan. 13, 1947 ; Jan. 13, 1947], Nos. 742/48 and 743/48. Class 39 (i). In a travelling-wave. amplifier the wave transmission path is a plurality of short helix sections traversed in succession by the beam. In one form, Fig. 1, the helix sections 8, 9, 10 have matched terminations 5, 6, 7 and the input and output are applied across and taken off from impedances 4 and 7 respectively. The left-hand ends of helices 9, 10 may or may not have terminating impedances. The helix parts may be of good conductivity material or of poor conductivity material coated partly or wholly with good conductivity material. In another form, Fig. 2 (not shown), there are only two helix parts, the second one having a smaller pitch than the first. The first part is designed so that the electron velocity only slightly exceeds the wave velocity so that velocity modulation of the beam, but substantially no amplification of the wave, occurs. The velocity and/or density modulated beam generates a wave in the second helix part. In all cases, the last few turns of at least one of the helix parts, e.g. the second helix part in Fig. 2 (not shown), may be made of or coated with resistive material to further reduce wave reflections. The Specification as open to inspection under Sect. 91 states that the second helix of Fig. 2 (not shown), may be replaced by a plurality of helices in order to obtain cascade amplification. This subject-matter does not appear in the Specification as accepted.