GB739165A - Improvements in or relating to pulsed radar systems - Google Patents

Abstract

739,165. Pulse radar; cathode-ray tube circuits. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Nov. 3, 1953 [Nov. 12, 1952], No. 28562/52. Class 40 (7). Relates to a pulse radar having a P.P.I.' display in which the output, Fig. 2 (a) from a pulse generator A, Fig. 1, triggers a flip-flop B whose output (b) controls the duration of the voltage output (g) from a time base generator C which is applied to the rotor of a magslip G producing two resolved sawtooth currents for the deflection coils E of the C.R.T. A sawtooth output (c) from C is applied to a discriminator D of the type disclosed in Specification 718,059 which produces positive and negative pulses (d) when the forward and back strokes of the sawtooth pass through the mean level ML of the sawtooth waveform, the cathode-ray beam being at the centre of the screen at such instants. The positive pulses (d) are applied to trigger the transmitter and also a flip-flop F whose output (f) is applied to intensify the cathode-ray beam during the effective portion T2-T3 of the forward sweep of the time base. According to the present invention the flipflop F, Fig. 4, comprises a cathode-coupled pair of triodes V1, V2 (normally cut-off and conductive respectively), the anode of a normally cut-off triode V3 being directly connected,to the anode of V2. The positive pulses from D applied to the grid of V1 trigger the flip-flop and the waveform (g) from C is applied to the grid of V3 so that at time T3, V3 becomes conductive and terminates the positive output pulse (f) from the anode of V2, the flip-flop being restored to its equilibrium condition at time T4 by the negative pulse from D; the positive pulse portion of waveform (g) is preferably extended beyond time T4 by an R.C. circuit. Alternatively an inverted form of waveform (b) may be applied to the grid of V3. The use of V3 ensures that the termination of pulse (f) is independent of the response time of the flip-flop thus allowing the use of triodes even though the time base speed is high. The rise time of the leading edge of pulse (f) is rather lengthy but this effect can be offset by advancing the timing of the positive trigger pulses from D. A known form of flipflop using a pair of cathode-coupled pentodes and diode clamps for terminating the output at a selectable time is illustrated in Fig. 3 (not shown).