GB1315869A - Travelling wave tubes - Google Patents

Abstract

1315869 Travelling wave tubes SIEMENS AG 18 Dec 1970 [23 Dec 1969] 60350/70 Heading H1D In a travelling wave tube an electron beam is projected from a beam generating system 1 to a collector electrode 4 via a single continuous delay line system including a first section that has a given specific delay time, and a second resonant section 8 that is inserted adjacent the collector electrode end of said system and has a delay time that is constant throughout its length or varies along its length but is at all points greater than the said specific delay time, the resonant section being formed by reflection forming discontinuities and having a length equal to a whole number multiple of halfwavelengths of that wavelength on the line corresponding to the mean operating frequency. The resonant section may be constant or varied in step-wise or continuous fashion or may have alternate greater or smaller c/v values varying in step-wise or continuous manner. The c/v variations can be obtained by variation of coil diameter or pitch or by metallic or dielectric sheathing. The beam may be focused by a conventional magnetic field system using coils or permanent magnets to produce a constant or periodic field. Sections 6 and 7 are separated by a decoupling reflection free attenuator 5 and terminal section 9 connected to output line 3 and circulator 10. The reflection forming discontinuities may have reflection factors of different values but are preferably of equal magnitude, these values determining the Q value and effective bandwidth. Terminal section 9 has a length equal to one or more quarter wavelengths to act as a transformer and ensure there is no further interaction with the beam. Efficiency may be improved by an increase in the field strength within the section 8, and by the provision of "depressed collector" operation.