GB612250A - Pulse-signal generator - Google Patents

Abstract

612,250. Valve pulse generating circuits. HAZELTINE CORPORATION. May 21, 1946, No. 15407. Convention date, June 6, 1945. [Class 40 (vi)] A pulse-modulated transmitter for a radar or direction-finding system which produces pulses of a predetermined duration, comprises an oscillation generator normally maintained in a non-conductive condition, means for supplying to the generator a control signal which initiates and maintains it in an oscillatory condition and a time-delay circuit which in response to the initiation of the oscillation, produces a potential which cuts off the initiating signal applied to the generator and renders it non-oscillatory at a predetermined time interval after the commencement of the oscillations, thus producing a pulse-modulated oscillation having a duration equal to this time interval. In the Figure, when a synchronizing pulse is applied at terminal 35, the amplifying valve 37 is rendered conducting and the blocking oscillator valve 25 is triggered by a pulse derived from the coupled windings 26a and 26b of transformer 26 producing a pulse in its output circuit, which is adjusted to be of longer duration than the pulse signal that the transmitter is required to generate. Amplifying valve 30 conducts and produces a positive pulse between the anode and cathode of the oscillator valve 10 which is rendered conducting after a short time interval to initiate oscillations of a frequency dependent on the tuned circuit 11, 12 in the aerial circuit 51 and in the coupled winding 41. The signal across winding 41 is rectified and the resultant positive pulse appears after a time interval dependent on the constants of the network 42, 43 across the resistor 44 which is chosen to terminate correctly the delay line. Valve 45 conducts and terminates the pulse from blocking oscillator valve 25 which will thus terminate the oscillations in oscillator valve 10. The duration of the oscillations produced by the transmitter will thus depend only on the delay in the network 42, 43, Fig. 2 (not shown). In a modification, Fig. 3 (not shown), the rectification in the grid circuit of the oscillator valve is used in place of the rectifier 40 of Fig. 1 to derive a negative pulse which is amplified in a single stage before being applied to the delay line circuit.