Patent GB-664041-A (GB)
Title: Improvements in or relating to electron discharge devices adapted for frequency changing
IPC: H03L7/16
Filed: 1947-08-08
Abstract: 664,041. Velocity-modulated tubes. SPERRY GYROSCOPE CO., Inc. Aug. 8, 1947 [July 12, 1943], No. 22126/47. Class 39 (i). [Also in Groups XXXV and XL (c)] Electron velocity modulation apparatus comprises three resonant circuits, preferably cavity resonators, traversed in succession by the beam; the first two circuits are excited by different frequencies and the beam modulated at both frequencies then passes through a drift tube to cause bunching, the bunched beam exciting the third circuit at the sum or difference frequency. The frequencies of the second circuit and first circuit may or may not be harmonically related; if they are harmonically related as in Fig. 9 the output frequency of the third circuit will also be a harmonic of the fundamental first circuit frequency but one which differs in order by unity from that of the second circuit. In one form, Fig. 5, the input signal of frequency ten units is fed into resonators 32, 52 of two velocity modulation tubes each having indirectly-heated cathode 35, 61, resonators 31, 32, 33; 51, 52, 67 and stepped collectors 48, 59. Resonator 31 is kept oscillating at a frequency of eleven or nine units by feed-back and the electron beam from cathode 35 is therefore velocity-modulated at frequencies of eleven (or nine) and ten units, is bunched in drift space 34, and excites resonator 33 at the difference frequency of one unit which may be taken off for utilization at 75. Part of the output is passed to resonator 67 via optional amplifier 70, preferably of the velocity modulation type, and density modulates the beam from cathode 61. This beam is velocity-modulated at a frequency of ten units by resonator 52, is bunched in drift tube 54, and excites the sum or difference frequency of eleven or nine units in the resonator 51, the output from 51 being fed back to resonator 31. The stepped shape of the collectors 48, 59 prevents secondaries being returned into resonators 33, 51 and allows for good heat dissipation; the collectors may be integral with or sealed to the resonator wall. Cathode 61 is mounted on a tube 64 with flange 65. A capacitative high-frequency by-pass coupling is formed between flange 65 and resonator wall 68 and/or between tube 64 and resonator wall 68<SP>1</SP>. Insulating closures 49, 69 complete the vacuum. The input line 71 is a coaxial line or wave-guide, and output lines 74, 75 are coaxial lines. In a modification, tube 29 may be used solely as a frequency multiplier in which case line 72 is disconnected from resonator 52 or the tube has no resonator 52. The beam is density-modulated at a frequency of one unit and excites the output resonator 51 at a frequency of eleven units. If the input is from a crystal stabilized oscillator of low power the tube 29 can be used as a stabilized highpower source for any of the frequencies one unit, eleven (or nine) units, and ten units. In a modified form, Fig. 6 (not shown), two separate velocity modulation devices similar to device 28, Fig. 5, are combined into a single system. If the system of Figs. 5 or 6 is inserted in the output of a high-frequency source, such as a velocity-modulation tube, of frequency 10 units, the output of 1 unit from the system is compared with a generator of reference frequency in a discriminator and the output from the discriminator is fed to a control device such as a control electrode for the source, then any deviations in frequency of the source may be automatically corrected, Fig. 8 (not shown). In another form, Fig. 9, an input of frequency 300 megacycles is converted to two outputs of frequencies 3000 and 3300 megacycles respectively, by means of two velocity modulation tubes having resonators 127, 128, 129; 133, 134, 135, 136, respectively. The beam from cathode 126 is velocity-modulated by the signal in resonator 127, and by resonator 128 excited at 3000 megacycles by feed-back, the sum frequency of 3300 megacycles being extracted and applied to resonator 134. The signal at 300 megacycles is applied also to resonator 133. Thus the difference frequency of 3000 megacycles is produced in resonator 135, and " buffer " resonator 136 extracts energy at 3300 megacycles. The 3300 megacycle energy may also be taken from resonator 129 or 134. The resonators 128, 135; 129, 134 may be combined into single chambers as in Fig. 6 (not shown). In Fig. 10, resonators 146, 147, 148 are traversed by electron beams of small diameter from cathodes 149, 162 in opposite directions. Due to radial debunching the beam concentrations are spread out laterally so that if disc 158 removes the outer part of the beam from cathode 149 the remaining part of the beam has its bunches and rarefactions inverted as described in Specification 605,257. This is stated to affect the mixing action advantageously. The apertured disc 158 may have any desired size of aperture or may be replaced by a grid. A. similar apertured disc may be used in. Fig. 5, or the outer part of the beam may be removed by the drift tube wall. Similarly conical member 169 has a small exit aperture so that it can remove the outer part of beam from cathode 162. The drift tube is completed by conical member 168. The other drift tube is formed by conical member 155 and tube 156. Conical member 153 is also provided. Specification 523,712 is referred to. The Specification as open to inspection under Sect. 91 is not limited to velocity-modulation apparatus but suggests that the mixing, multiplying, and automatic frequency control arrangements are of general application. The device of Fig. 6 may be formed with two separate sets of resonators, each set being similar to device 28, Fig. 5. The automatic frequency control arrangements may include electronic and/or motor driven mechanical tuning means as described in Specification 670,551, [Group XL (c)]. This subject-matter does not appear in the Specification as accepted.