Patent GB-678713-A (GB)
Title: Improvements in or relating to apparatus for varying the impedance between a source of high-frequency alternating-current electrical energy and a load circuit
IPC: H01J25/28
Filed: 1947-05-30
Abstract: 678,713. High frequency discharge apparatus. SPERRY GYROSCOPE CO., Inc. May 30, 1947 [May 31, 1946], No. 14460/47. Class 39 (i). [Also in Group XL (c)] Apparatus suitable for supplying ultra high-frequency energy from a source to a utilization device consists of a transmission line (for example a waveguide) having a first portion coupled to the source and to the two electrodes defining the velocity modulation region of a reflex klystron and a second portion coupled to these two electrodes and to the utilization device, the electrical parameters of the klystron being variable within a range such that self-oscillations are not caused in the apparatus, the klystron acting as a variable impedance which may be controlled by variation of the electrical parameters. It is shown mathematically and graphically that by varying the potentials applied to the klystron, preferably the control grid and reflector electrode potentials, any desired combination of resistance and reactance, positive or negative, may be obtained, and the impedance will be linear for small signals and non-linear for large signals. Fig. 7 shows a klystron 25 wherein the velocity modulation grids G<SP>1</SP>, G<SP>2</SP> have external flanges designed to fit flush into a section of wave-guide; the tube may be integral with the wave-guide, Fig. 8 (not shown), and one of the grids G' may be spaced away from the wall of the wave-guide to which it is connected, Fig. 8A. Fig. 17 shows a modification for use with coaxial lines, the tube having a metal envelope to which are connected two diaphragms D<SP>1</SP>, D<SP>2</SP> which fulfil the function of the grids G<SP>1</SP>, G<SP>2</SP>; the outer conductors of the lines are connected to the envelope whilst the inner conductors are connected to a cylinder between the diaphragms, the cylinder being of such a length that the transit time is half a cycle. The klystron may be used as an amplifier or repeater by making its reactance zero and its conductance negative but numerically smaller than the conductance of the load; it may also be used to modulate signals passing in the line to which it is coupled and as shown diagrammatically in Fig. 12 modulating signals 58 may be applied through a klystron 25 to turn the cavity resonator of an oscillator 54. Another application, Fig. 14, is to use two klystrons 25<SP>1</SP>, 25<SP>11</SP> feeding two loads 37<SP>1</SP>, 37<SP>11</SP> from a single source 36, so that the proportion of energy fed to each source can be controlled by the potentials applied to the klystron; one of the loads might be a monitoring device. A modification of this arrangement, Fig. 15 (not shown), is used for an aerial beam switching system, power being directed to one or other of two aerials in accordance with the potentials on two klystrons. Advantage may be taken of the non-linearity of the impedance to use the device as a signal expander or conversely as a signal limiter. Figs. 18 and 19 show klystrons combined with a resonator 21; they may be used in the same way but in addition they may be used to provide a resonator of which the Q and the operating frequency may each be controlled by varying the potentials or the tube. The Specification as open to inspection under Sect. 91, comprises also using a klystron as a pure reactance coupled in parallel with a magnetron and used to tune it, Fig. 13A (Cancelled) (not shown). If the magnetron is pulsed the klystron should also be pulsed to maintain its impedance constant; tuning is controlled by varying the reflector voltage and modulating voltages may be applied to the cathode or the reflector. Similarly, a klystron may be used to amplitude modulate a three resonator klystron, Figs. 13B and 13C (Cancelled) (not shown), or to control the feedback in a two-resonator klystron, Fig. 30 (Cancelled) (not shown). A klystron may be used as a noise generator, covering a particular frequency load and all its harmonics; it is stated that a second klystron may be used to fill the gaps in the spectrum left by the first. A klystron combined with a resonator, as in Figs. 18 and 19, may be operated at a point at which oscillations are possible but are not self-starting; if a signal is applied to the tube oscillations start and continue so that the tube acts as a " memory " tube in remembering the applied signal. This subject-matter does not appear in the Specification as accepted.