Patent GB-660269-A (GB)
Title: Improvements in microwave coupling and modulation apparatus
IPC: H01J25/52
Filed: 1948-06-08
Abstract: 660,269. Electron discharge apparatus. RADIO CORPORATION OF AMERICA. June 8, 1948 [June 14, 1947], No. 15456/48. Class 39 (i). [Also in Group XL (c)] A magnetron device for variably coupling to a load circuit or amplitude modulating microwave energy comprises a magnetic field H coaxial with the electron beam, a microwave electric field of frequency 1/2#.e/m.H applied transverse to the beam to cause the electrons to follow spiral paths with radii dependent on the energy absorbed from the electric field, energy abstracting means adjacent the beam causing a reduction in the radii of the paths, and means controlling the energy of the beam. Either the control grid or an accelerating grid of the electron beam gun acts, by varying the beam current or electron transit time, to modulate or control the output energy. Between the electron gun and a final collector electrode may be arranged two pairs of electrodes, parallel or at right angles, and at equal or spaced distances along the beam, serving respectively as the field applying electrodes and abstracting electrodes, or one or both electrode pairs may be formed by re-entrant portions of apertured cavity resonators through which the beam passes, resonant to the microwave frequency. The electrons all lie at any instant on a revolving generator of a cone at the input and output electrodes or on a generator of a cylinder between the cones. In Figs. 7, 8, a plurality of electron beams pass between radial vanes 75, 89, alternately connected by straps 91, 93, and energized in push-pull by the microwave energy, to a common collector electrode 97. Connected to the latter and telescoped with the vanes 75, 89; are arcuate electrodes 21 forming with re-entrant tongues 19 of an output cavity resonator 25 the energy abstracting electrodes, the collector electrode 97 being insulated from the wall of the resonator by a support 99. In a modification (Fig. 10, not shown), two axially spaced aligned groups of alternately connected vanes are used, a single loop projecting between one pair of vanes abstracting energy from the output group. In a further modification (Fig. 13), a thermionic cathode 149 is arranged coaxially with an upper group of radial vanes 75 alternately connected at their inner ends by rings 91 and connected at their outer ends to a common anode-forming metallic envelope 121 so that the upper group of vanes 75 form a self-excited magnetron with transverse electric field. An apertured shield 145 separates the upper vanes from the energy abstracting lower vanes 135. In Fig. 15 the electron beam passes through an apertured anode 7, and through shielded input and output cavity resonators 37, 39, having mounted therein oppositely facing arcuate electrodes 41, 43 and 59, 61 supported by insulating brackets from a common metal envelope. Input and output loops are arranged to produce and abstract transverse electric energy in the resonators and connect through tapered conductors to transmission lines. Tuning elements 189, 211 capacitatively bridge the electrodes in each resonator and are adjustable from outside the tube envelope by threaded control shafts acting on bellows assemblies. Water jackets 159, 165 cool the envelope and collector electrode 11 and an observation window is provided.