GB630005A - Improvements in or relating to high frequency electron discharge tube structures - Google Patents

Abstract

630,005. Velocity-modulated tubes. SPERRY GYROSCOPE CO., Inc. July 4, 1944, No. 12764. Convention date, July 21, 1942. [Class 39 (i)] [Also in Group XL (c)] A high-frequency electron discharge tube structure comprises means for producing a plurality of electron beams and for projecting them first through a cavity resonator to vary the velocity of the electrons to initiate bunching and then through a second resonator to extract energy from the beams ; means are provided for effecting progressive phase shifts between the bunched beams as they enter the second resonator and/or for effecting progressive phase shifts of the high-frequency voltages encountered by the beams upon passing through the second resonator. Phase shift between the bunched beams may be produced by excitation of the first resonator in a suitable mode or by adjustment of the transit times of the beams between the two resonators. Phase shifts of the high-frequency voltages encountered by the beams upon passing through the second resonator may be produced by causing the resonator to oscillate in a suitable mode. The apparatus may be employed as a push-pull amplifier or oscillator or as a frequency multiplier or converter. The apparatus shown in Fig. 1 comprises a buncher resonator consisting of nearly cylindrical chambers 3, 3<1> communicating with one another over a medial sector and connected to chambers 4, 4<1> of a similarly shaped catcher resonator by drift tubes 14, 14<1>. Beams from hot cathodes 1, 1<1> are modulated by grids 2, 21 and subjected to velocity modulation by pairs of grids 10, 9 and 10<1>, 9<1> ; the beams interact with the catcher field by pairs of grids 12, 13 and 12<1>, 13<1> and impinge on collector electrodes 15, 15<1> having cooling ribs 16, 16<1>. Tuning of the buncher resonator is effected by a knob 22 adjusting a dielectric. cylinder 17 enclosed in an evacuated glass envelope 18 ; tuning of the catcher resonator is similarly effected. Supply of high-frequency energy to the buncher resonator is effected by concentric lines 5, 5<1> and loops 7, 7<1> or alternatively by a common loop 25, the choice being determined by the desired mode of oscillation. Similarly, energy is withdrawn from the catcher resonator by loops 8, 8<1> or a common loop 26. Different modes of oscillation are illustrated in Figs. 5, 6 in which the section of the resonators is shown modified to favour the given modes. In the arrangement shown in Fig. 12 the grids 2, 2<1> are modulated in opposite phase at frequency w<1> from a transformer 76. High frequency energy of frequency w is supplied at 71 and high-frequency energy is withdrawn at 72. The cathode 1<1> is connected to a D.C. voltage higher than that of the cathode 1 the difference being such that the difference in electron transit times is one half period of the operating frequency. As shown, the buncher and catcher resonators are both arranged to oscillate as in Fig. 5 ; alternatively they may both oscillate as in Fig. 6. As a result of opposite modulation by the grids 2, 2<1> the output from the catcher consists of the side-band frequencies w+w<1> and w - w<1>, the carrier-frequency w being suppressed. By sharply tuning the carrier resonator to one of the side-band frequencies the other side band also may be suppressed. In a modification both cathodes are connected to the same voltage and the required phase shift is produced with a buncher oscillating as in Fig. 5 and a catcher as in Fig. 6 or vice versa. Modifications are described employing three and four beams. In such arrangements one side-band as well as the carrier may be suppressed. In apparatus having n beams each beam is modulated with the same signal but with a phase difference of 360 degrees/n. For a frequency multiplier the catcher resonator is designed to have a frequency which is an harmonic of that of the buncher resonator. Specifications 523,712, 531,251, 602,164 and 640,895 are referred to.