GB627404A - Improvements relating to electrical discharge means, particularly pulse-generating means and blocking oscillators for use therewith - Google Patents

Abstract

627,404. Pulse generating circuits. SPERRY GYROSCOPE CO., Inc. May 10, 1945, No. 11804. Convention date, May 10, 1944. [Class 40 (vi)] A pulse generator comprises a blocking oscillator valve the feed-back transformer of which has a primary winding in series with the valve output electrode and a secondary winding in series with a biassed control electrode, a " throttling " resistor which is preferably variable limits the grid current and enables the pulse duration to be adjusted being connected in series with a coupling condenser between the control electrode and the secondary winding. In Fig. 1 the " throttling " resistor 25 is connected in series with condenser 23 between the control grid of the valve and the secondary winding 18 of the feed-back autotransformer 12. The variable grid leak resistor 24 enables the pulse repetition rate to be adjusted. The blocking oscillator operates in the normal manner but the resistor 25 limits the grid current of the valve, thus enabling sharper pulses to be obtained, Figs. 3A, 3B, C3 (not shown), and the duration of the conduction period of the valve to be varied. The provision of switch 27 in the control grid circuit of the oscillator valve enables the blocking oscillator to operate under four different conditions. When contact 29 is made the control grid is biassed to a high positive potential, the charging curve of condenser 23 intersects the cut-off voltage line of the valve at a relatively large angle, Fig. 4 (not shown), and a highly stabilized pulse repetition rate is obtained. At position 31 the control grid circuit is returned to cathode and the blocking oscillator is readily synchronized by pulses from generator 37. At position 32 the control grid is biassed highly negative and the blocking oscillator only operates in the presence of positive triggering pulses from generator 37. At position 33 the pulse repetition rate of the oscillator may be stabilized with respect to variations in power supply voltage by adjustment of contact 36 on potentiometer 35. Resistors 24, 25 are preferably so chosen that the change in frequency of the oscillator caused by variation of resistance with temperature is substantially negligible. In a modification, Fig. 2, the pulse transformer 12 has separate but tightly coupled -windings and a portion of the grid leak resistors 62, 63 may be switched in or out to vary the pulse repetition frequency. Separate outputs are taken from the blocking oscillator to cathode follower stages 56, 57 which are biassed so that only positive pulses appear at their outputs, Figs. 3D, 3E (not shown). The output at terminal 58 is derived from the positive portion of the waveform generated by the oscillator and that at 61 from the negative portion, and there is thus a delay between these two positive pulses corresponding to the delay between the leading and trailing edges of the positive pulses at terminal 26 of the oscillator, Fig. 3C (not shown). The positive pulses at terminals 58, 61 may be used to trigger two other oscillators with a prescribed time interval between them. Specification 469,898 is referred to.