GB987284A - High frequency apparatus - Google Patents

Abstract

987,284. Travelling wave tubes; particle accelerators; microwave filters. VARIAN ASSOCIATES. Jan. 11, 1962 [Feb. 27, 1961], No. 1105/62. Headings H1D and H1W. High frequency apparatus has a slow wave structure comprising a plurality of coupled cavity resonators 28 of the coaxial cavity type, the coupling between adjacent resonators being such as to provide negative mutual inductive coupling thus causing a reduction in the resonance frequency in the T1 mode of operation while not substantially affecting the resonance in the " O " mode of operation. The apparatus may be used in a forward or backward wave travelling wave tube or in a particle accelerator, apertures being provided in the end walls 24 of the cavities and the conducting bar 27 of each cavity for the passage of an electron beam from an electron gun. Negative mutual inductive coupling is obtained by providing coupling apertures 35 in the end walls of the resonates with or without the provision of a loop 34. In a travelling wave tube operating on the first space harmonic, the time of flight of electrons through one cavity is three-quarters of a cycle, whilst the time of flight through the thickness of one of the bars 27 is one-half cycle. The bar need not be perpendicular to the beam axis as shown, but it may be inclined and attached to the end walls of the resonators, Fig. 6 (not shown) or it may extend parallel to the beam axis from each end wall and have a central portion perpendicular to the beam axis, Figs. 5a, 5b (not shown). For coupling energy into or out of the structure one of the bars may extend through an aperture in the waveguide 26 and terminate on a wall of an input or output waveguide arranged adjacent waveguide 26.