Patent GB-783775-A (GB)
Title: Improvements in or relating to electron discharge devices employing cavity resonators
Inventor: PEARCE ALBERT FREDERICK
IPC: H01J25/18
Filed: 1953-04-10
Abstract: 783,775. Microwave couplings. ELECTRIC & MUSICAL INDUSTRIES, Ltd. March 23, 1954 [April 10, 1953], No. 9726/53. Class 40 (8). [Also in Group XL (a)] An electron discharge device has a toroidal cavity resonator having opposed walls provided with annular apertures through which an annular or sheet-like electron beam is projected, and energy transferring means for feeding energy in or out are formed by an aperture or apertures in the resonator wall separate from the openings forming the annular beam passage gap, the energy transferring aperture or apertures being uniformly disposed around the resonator to load the resonator uniformly and so to reduce the liability of the resonator to resonate in an unwanted mode. The more uniform transfer of energy around the cavity resonator reduces the tendency of the resonator to oscillate in an unwanted mode. In one form, Fig. 1, the cathode 4, resonator 1 and reflector 7 are annular ; the cathode may alternatively be outside, and the reflector 7 inside, the resonator. The emissive surface of the cathode may be plane or concave, and the cathode is carried by a ceramic block 5. Screen electrodes 6 focus the beam into sheet form. 8, 9, 10 is a steel envelope the parts of which are welded together, and 11 is the pinch. Energy is extracted by means of an odd plural number, e.g. three or seven, apertures 12 uniformly disposed around the resonator which allow energy to pass via tapered coaxial line 13 to circular waveguide 14 operating on the Eg mode, the open end of the guide having a sealed glass window 19. The conical inner conductor is carried by disc 15 having boss 16 for supporting electrodes 4, 6 and the outer conductor has a flange 17 welded to steel plate 10 and carries ceramic block 18 supporting reflector 7. The apertures 12 may be circular or slot-like. In modifications the waveguide 14 may be replaced by a coaxial line the inner conductor of which is an extension of the cone, an annular glass window being provided, Fig. 2 (not shown). The apertures 12 can be replaced by an annular gap associated with a diaphragm, Fig. 3 (not # shown) or with a - transformer, Fig. 4 (not 4 shown). In a modification, Fig. 6, energy is extracted via an odd plurality of apertures 26 spaced #g apart to waveguide 25. The closed end 28 of the guide is tapered to avoid constricting the output end. Oscillators or amplifiers with two concentric or axially spaced resonators can be used, Figs. 7-10 (Fig. 9 only shown). In Fig. 7 (not shown) the resonators each have a plurality of circumferential apertures for mutual coupling, the feedback energy being confined by two parallel annular plates. In Fig. 9, which may be an amplifier, the input and output coaxial lines 40, 39 are similar and are coupled to the inner resonators via a plurality of apertures or an annular slot. For oscillator operation, the resonators are coupled by cylinders 34. The beam is generated by annular cathode 37. Alternatively the form of coupling shown in Fig. 6 may be employed, Fig. 10 (not shown). The inter-resonator coupling discs or cylinders are such as to further minimize undesired modes of oscillation in the resonators. Undesired modes have an even number of circumferential nodes from two upwards while the desired mode has no circumferential nodes.