Patent GB-729930-A (GB)
Title: Improvements in or relating to electron discharge devices
IPC: H03B9/02
Filed: 1952-06-30
Abstract: 729,930. High-frequency discharge apparatus. TELEFONAKTIEBOLAGET L. M. ERICSSON. June 30, 1952 [June 30, 1951], No. 16426/52. Class 39 (1). In an electron discharge tube oscillator or amplifier in which electrons oscillate, as in a Barkhausen-Kurz tube, between negative electrodes about a positive electrode and interact with a high-frequency electric field, a magnetic focusing field is provided to prevent the electrons from contacting the positive electrode, and a lateral drift motion is imparted to the electrons either by making the magnetic field inhomogeneous or by introducing an electric field or field component crossed with the magnetic field. The frequency of the high-frequency electric field is equal to, or a multiple of, or a submultiple of the frequency of oscillation of the electrons. The oscillating electrons drift in trochoidal paths, and are collected at the point where the amplitude of oscillation has fallen to zero. In the oscillator of Fig. 3, 1 is the cathode, 4, 41 the negative electrodes, 8 a resonant circuit connected between the negative electrodes, 2 the positive electrode, and 7 a collector electrode. The direction of the magnetic field is indicated by 5. The negative electrodes 4, 41 are inclined to one another so as to set up a parabolic potential distribution whereby the electrons oscillate with a frequency which is independent of their amplitude. The electron beam introduced from the cathode 1 may be intensity-modulated by further electrodes. Frequency modulation may be accomplished by applying an audio frequency voltage between the cathode and the negative electrodes. A bias voltage may be applied between these electrodes to control the average frequency of oscillation. In the amplifier tube of Fig. 5, three pairs of negative electrodes are arranged along the positive electrode (not shown). The signal voltage is applied between the electrodes 4, 4<SP>1</SP>, and the output voltage is taken from across the electrodes 24, 24<SP>1</SP>. Velocity-modulation imparted to the electrons between the electrodes 4, 4<SP>1</SP> is converted into intensity modulation in the field of the middle pair of negative electrodes, shown as connected together to form a single electrode 14. Grooves 10, 101 in the electrode 14 modify the field from a parabolic potential distribution in such a manner as to cause fast electrons to be delayed in relation to slower electrons by reason of their greater amplitude. Notches 11, 11<SP>1</SP> and 12, 121 are provided in the electrode pairs 4, 41 and 24, 241 for smooth transitions between the fields of the three sections. The electrode systems may be built into rectangular or circular wave-guides, Figs. 6 and 7 (not shown). The electrode system of Fig. 8 radiates energy directly. 25 is a permanent magnet coated on its inner surface with conductive material, for example silver, to form the negative electrodes 4, 4<SP>1</SP> and to serve as a resonator. In another arrangement, Fig. 9 (not shown), a central positive electrode is surrounded by a toroidal resonator.  The magnetic field is axial and the electrons oscillate in a cylindrical surface. The arrangement of Fig. 3 may be modified by providing a greater penetration of the positive electrode 2 into the region between the negative electrodes 4, 4<SP>1</SP>. The positive electrode 2 is then provided with a slot 30, Fig. 10b, through which the electrons oscillate. Positive electrodes 29, 29<SP>1</SP> provide the electric field component which with the magnetic field imparts the electron drift motion. In the arrangement of Fig. 10c the positive electrode is in two parts 2, 2<SP>1</SP> and the resonant circuit 8 is connected between them. The arrangement of Fig. 10c may be modified to form an annular arrangement, Fig. 11 (not shown), in which the electrode system surrounds a central cylindrical permanent magnet having end polepieces of greater diameter. A plurality of cathodes lying in the plane of the negative electrodes are provided. The tubes may be operated as frequency multipliers. The possibility of providing an arrangement in which electrodes are shaped as delay lines for supporting travelling waves which interact with the electrons, is referred to. The negative electrodes may be wholly substituted by cathodes. A formula is given for adjusting the electron current in relation to electrode dimensions and spacings, and electric and magnetic spacings field strengths to reduce noise. Specification 558, 143 is referred to.