| 摘要 |
710,669. Automatic frequency control systems. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Jan. 7, 1952 [Jan. 9, 1951], No. 470/52. Class 38(4) The treatment circuit of a short-wave medical apparatus is kept in resonance with the oscillations of a frequencystabilized 'source by comparing the phase of the voltages in the source and the treatment circuits, and deriving therefrom a control voltage for corrective adjustment of a tuning impedance in the treatment circuit. As shown in the diagram, the tuned circuit 8 of the h.f. source is inductively coupled to the treatment circuit 21, 22. A phase-comparing valve 1 which may be of the nonode type has one control grid 5 energized by a coil 7 coupled to the circuit 8, and the other control grid 6 coupled by a coil 11 in the treatment circuit. When the treatment circuit is in tune the two grids are excited in quadraturo relation. and departure from this relation increases or decreases the relative phase angle, and correspondingly affects the anode current through the resistor 3. A second phasecomparing valve 2 has its grids 5, 6 excited in constant quadrature relation, one directly by the coil 7 and the other by a tune circuit 9. 10 connected to the coil 7 by a condenser 23. The anode current through the resistor 4 thus balances the current through resistor 3 when the treatment circuit is in tune. Departure from correct tune creates a difference of voltage between the anode points 12, 13 and causes the anode current of one of the valves 15, 17 to predominate. A motor 20 is thus started up in one or other direction, according to which the opposed field-coils 18, 19 carries the greater current. The motor 20 adjusts a tuning-condenser 21 or other element of the treatment circuit to bring it to resonance. Alternatively the anode currents of the valves 15, 17 may operate a polarized relay by means of which a device for adusting the condenser 21 is controlled. The treating element may comprise capacitor electrodes or a coil. |
