GB623985A - Improvements in or relating to high-frequency electronic devices in which an electromagnetic field is caused to interact with an electron stream - Google Patents

Abstract

623,985. Velocity - modulated tubes. WESTERN ELECTRIC CO., Inc. Feb. 11, 1944, No. 2610. Convention date, March 7, 1941. [Class 39 (i)] In a velocity-modulation discharge tube the spacing between the grids 1, 2 of the buncher resonator 5, the ratio between the electron transmitting and electron obstructing areas of the grids 1, 2, and the average time rate of flow of the electrons in the beam are so interrelated that the impedance of the beam is made substantially equal to the resonant impedance of the resonator 5. The average time rate of flow of the electrons may be varied by varying the emission or the beam velocity, and the impedance of the beam is defined as the ratio between the peak value of the alternating voltage across the buncher grids 1, 2 considered as the space integral of the field between grids 1, 2, and the resultant current variation at the operating frequency produced in the beam between grids 1, 2. If a plurality of resonators are provided, the impedance of each of them is matched to the beam impedance. To obtain an impedance match in any particular case, the design parameters are adjusted so that the measured resonant impedance of the resonator is made equal to the measured beam impedance, the quantity actually measured in the latter case being the ratio collector voltage to collected microwave current, which bears a known linear relationship to the beam impedance as defined. To assist in the impedance matching procedure, the buncher 5 is excited at different frequencies above and below its resonant frequency and the microwave current in the collector circuit is measured for each frequency so that a resonance curve may be plotted. The width of the resonance curve gives an indication of the degree of impedance matching. The invention may be applied to amplifiers, oscillators, modulators and detectors; e.g. to a multi-stage amplifier, Fig. 4 (not shown), a constant frequency oscillator, Fig. 6 (not shown), or to a variable frequency oscillator, Fig. 7 (not shown), which may be used as a frequency modulation system.' The buncher resonator may be excited electrostatically, Fig. 5A (not shown). Specification 529,771 is referred to. The Specification as open to inspection under Sect. 91 states that the impedances of wave guides may be matched to the beam impedance. In general, the impedance matching need not be exact, but may be to " any desired degree." A construction utilizing a double field grid arrangement is described with reference to Fig. 12 (Cancelled, not shown). This subjectmatter does not appear in the Specification as accepted.