Logarithmisch-periodische Elektronenstrahlroehre

摘要

1,198,482. Velocity-modulated beam tubes. GENERAL ELECTRIC CO. 11 July, 1967 [29 Sept., 1966], No. 31960/67. Heading H1D. An electron beam device, in particular, a travelling-wave tube or klystron, comprises an interaction structure having an array of coupled elements so dimensioned and disposed that the interaction in the array is log periodic with frequency. The term "log periodic" when applied to an array of elements signifies that the elements are so dimensioned and disposed that some electrical property, e.g. impedance or resonant frequency, recurs at a succession of frequencies which form a geometric series. Such an array may have wide-band properties. As shown, the amplifier of Fig. 1 comprises an array 33 consisting of coupled resonant cavities 11-21 of annular form, the relevant dimensions of the cavities being progressively reduced in a fixed ratio from the input end to the output end of the amplifier so that they provide a geometric series of resonant frequencies. The resonant sections incorporate tubes 36-46 of decreasing length which define a drift space for an electron beam travelling from cathode 65 to anode 60. The cavities are coupled by a line 79 which extends from input terminals 78 to output terminals 781. Different frequency components in the input and output signals interact with the electron beam at different positions along the length of the array. In a modification (Fig. 2, not shown), the array consists of a helix of progressively reduced pitch and diameter defining a surface of frusto-conical form. In a further modification the array is in the form of an interdigitated series of annuli which again define a structure of generally frusto-conical form (see Fig. 3, not shown, and Specification 1,198,483). The invention may be applied to devices using both fast and slow waves and operating in either forward or backward modes. The devices may use, in addition to those shown, bifilar and magnetron type arrays. The generating ratio of the geometric series on which the arrays are based preferably lies between 0À90 and 0À95.