GB1105220A - Dual mode travelling wave tube - Google Patents

Abstract

1,105,220. Travelling wave tubes. INTERNATIONAL STANDARD ELECTRIC CORPORATION. 30 Sept., 1966 [Oct. 4, 1965], No. 43825/66. Heading H1D. A travelling-wave tube amplifier operable either under continuous wave or, at a higher output, under pulsed conditions, includes a first slow wave structure for stable amplification under continuous wave operation, in tandem with, D.C. insulated from, and R.F. coupled to, a further slow wave structure dimensioned to provide power amplification at a higher D.C. voltage than the preceding slow wave structure, the R.F. output of the tube being taken from the further slow wave structure in both modes of operation. The first helix 10 is provided with attenuating means, and may have a sever, and be coupled to the second helix 20, of larger diameter, by an overlapping portion of the further helix, of an altered pitch chosen to provide impedance matching (Fig. 2, not shown); alternatively, the two helices may be coupled, respectively, to the inner and outer conductors of a coaxial line coupling section (Fig. 3, not shown). For C.W. operation, the potential applied, via R.F. choke 30, to the second helix 20 is preferably the same as that of the first helix 10; for pulsed operation, ganged switches 24 and 28 increase the potential of helix 20 and apply a pulsed input to the modulating anode 26. In alternative methods of connection for pulsed operation, the pulsed voltage is applied to the gun cathode, or directly to the second helix. Depressed collector operation may be employed. Operating parameters are given. The diameter of the envelope preferably varies with the two helix sections as shown, to facilitate the provision of appropriate permanent magnet focusing systems.