GB526584A - Improvements in or relating to electrical frequency dividing systems - Google Patents

Abstract

526,584. Valve circuits. RADIO AKT.-GES. D. S. LOEWE. March 21, 1939, No. 8950. Convention date, March 22, 1938. [Class 40 (v)] In a frequency divider the controlled low frequency oscillating system is made sensitive to synchronization by the higher frequency oscillation during only a short fraction of the period of the controlled oscillation, thus preventing errors in the phase or frequency of the divided frequency. The hexode valve has its anode back coupled by inductance 7 to the grid circuit 1, 2, which is tuned to the low frequency. The grids 4a, 4c, are coupled to the circuit 1, 2, by inductance 3 and phase shifting network 5, 6, in such a manner that anode current can only flow in the valve in short pulses corresponding to the period when both grids are positive. This time is made to coincide with one period of the higher frequency synchronizing oscillations which are applied from 10 to the screen grid 4d. The bias or grid 4d is normally so low that oscillation in the tube is prevented and is only possible during a positive period of the control oscillations. The system thus adjusts itself so that the positive pulse produced by the low frequency oscillations coincides with a positive half-wave of the control frequency. Negative potential pulses are obtained at the terminals of resistance 12, but a sinusoidal output may be obtained by the use of simple or coupled oscillatory circuits 13, 14, 13a, 14a. A number of such frequency dividers may be used in cascade particularly for obtaining a large number of lines in television; 441 for example is equal to the product of the four prime factors 7. 7. 3. 3. The invention is also applicable to systems in which the frequency is determined by resistancecapacity combinations. Specification 491,450 is referred to.