GB587464A - Improvements in electric pulsing circuits - Google Patents

Abstract

587,464. Pulse generating circuits; radiolocation. WESTERN ELECTRIC Co., Inc. July 25, 1944, No. 14231. Convention date, May 13, 1943. [Class 40 (v)] In a pulse generator, a tuned circuit is set in oscillation in response to a short initiating . pulse, a rectifier preventing reverse charging of the condenser in the tuned circuit by energy stored in the inductance, and the potential set up across the inductance being utilized to produce a rectangular pulse. As shown, a variable long pulse is produced by a short initiating pulse, and may be used for blanking purposes. At the end of the long pulse, a short delayed pulse is produced similar to the initiating pulse. The delayed pulse may be used to simulate an echo of a transmitted pulse as represented by the initiating pulse. Alternatively, the delayed pulse may be used to initiate a time base circuit a desired time after the transmitted pulse. The blanking pulse may be added to the video signals in a radar set to blank out signals between the transmitted pulse and a predetermined point. Blanking pulse. A short negative impulse applied to the grid of valve V1 is amplified and applied as a positive pulse to the grid of valve V2 biassed beyond cut-off, in the anode circuit of which is a tuned circuit T1. The sudden increase of anode current causes the tuned circuit to oscillate, the upper terminal going rapidly negative and then more slowly positive at the natural frequency of the tuned circuit. The negative part of the waveform is applied to the grid of valve V4, but the subsequent positive half-cycle is suppressed by diode V3. The negative signal on the grid of valve V4 produces a positive pulse at the anode which is applied to valve V5 biassed beyond cut-off, a negative pulse being produced in the anode circuit which may be used as a blanking pulse. Delayed pulse. The positive pulse from valve V4 is applied to the grid of valve V6 biassed beyond cut-off, the sudden increase and decrease of the anode current causing the tuned circuit T2 to oscillate. The oscillation generated at the beginning of the pulse is rapidly damped out by diode V7 since the first crest is of negative amplitude, the oscillation produced at the end of the pulse being damped out after the first positive crest. This waveform is applied to the grid of valve V8 biassed beyond cut-off to produce a short negative pulse in the anode circuit which is applied to the grid of valve V9. The positive pulse from the anode of valve V9 is applied to the grid of valve V10 biassed beyond cut-off to produce a negative pulse in the anode circuit. With the switch 170 in the position shown, the undelayed pulse is taken from the grid of valve V2 and mixed with the delayed pulse in valve V9 so that both the delayed and undolayed pulse appear in the anode of valve V 10. The adjustment of the tuned circuit T1 varies the time delay between the pulses and adjustment' of tuned circuit T2 varies the width of the delayed pulse.