GB706242A - Improvements in or relating to circuits for automatically tuning the output circuitsof high-frequency oscillation generators - Google Patents

Abstract

706,242. Automatic tuning control systems. PHILIPS ELECTRICAL INDUSTRIES, Ltd. May 19, 1952 [May 22, 1951], No. 12598/52. Class 38 (4) The load circuit 10 of a high frequency oscillator, used for example in medical treatment, is automatically maintained in resonance with the oscillator output by the use of two phase-comparing valves 3, 4, one input grid 5 of each valve receiving a fraction of the oscillatory voltage of the primary oscillatory circuit 7, and the other input grids 6 being connected to opposite ends of a coil 9 centre-tapped to earth and coupled to the load circuit 10. When the load circuit is in tune, the voltages on 5, 6 are in quadrature and result in equal voltages across the anode resistors 1, 2 ; the mis-tuning causes a departure in opposite directions from the quadrature relation giving a rise in voltage at one anode and a fall at the other. The rising voltage, applied to the grid of one of a pair of thyratrons 11, 12 causes ignition of that tube and current passes from an A.C. supply through the armature 21 and one or other of the field coils 13, 14 of a reversing motor which is geared to a tuning condenser 15, thus bringing the load circuit into tune with the oscillator. Stray fields are prevented or rendered ineffective by screening the high-frequency leads, the thyratrons 11, 12, and the phase-comparing valves 3, 4 which may be of the nonode type. The point of ignition of the thyratrons is adjustable by a potential-divider 16, and a common cathode resistor 19 prevents them from firing simultaneously. Variable cathode resistors 17, 18 permit initial balancing of the valves 3, 4. Operating current is supplied to the tubes by supply leads I ... VI.