GB724606A - Improvements in or relating to time dividers for use in radar apparatus - Google Patents

Abstract

724,606. Radar; pulse circuits. PHILIPS ELECTRICAL INDUSTRIES, Ltd. May 22, 1953 [May 26, 1952], No. 14490/53. Classes 40 (6) and 40 (7). A radar system has a main pulse generator coupled to a plurality of pulse frequency-dividing stages for producing control pulses of the desired pulse-recurrence frequency. A selector pulse generator is connected to the divider chain and provides selector pulses, the rear edges of which are synchronized with the control pulses and which are used to gate a selector stage connected to the main pulse generator to periodically release trigger pulses. Distance marking pulses are derived from one or more of the divider stages for the indicator. In one embodiment an oscillator 1 controlled by a crystal 2 feeds main pulse generator 3, the pulses from which are fed to divider chain 4, 5, 6, 7 and 8. The trigger frequency pulses from divider 8 are used in unit 11 to synchronize selector pulses so that their rear edges correspond in timing to the frequency-divided pulses. The selector pulses are used to open gate 12 to pass approximately two pulses from generator 3, the first of which is effective to trigger blocking oscillator 13 to produce output pulses fed over line b to synchronize the time-base generator, through delay line 14 and over line c to modulate the transmitter, and through delay line 14 and over line d to synchronize the sawtooth generator 15 controlling the swept gain of the receiver. Switch 9 selects pulses from various points on the divider chain to use as range markers on the display. The selector circuit is shown in Fig. 4. The final pulse frequency-divider stage consists of blocking oscillator 18 which feeds a sawtooth waveform (Fig. 3 (a), not shown), cutting off sharply at the instants corresponding to the control pulses through resistor 22 to the grid of selector pulse generator 21. Valve 21 is normally cut off but produces a substantially rectangular pulse between the time the sawtooth reaches a certain value and the cut-off time. To obtain constant width selector pulses the circuit of valve 21 is stabilized by negative feedback resistor 23 and a resistor 25 in series with the screen-grid stabilizing tube 24. The output pulses are arranged to be substantially rectangular by utilizing positive feedback for A.C. only through triode 26. The selector pulses are fed to valve 34 to gate the pulses fed in at 32 from unit 3. The first of these to be effective initiates blocking-oscillator action to generate the trigger pulses which are shaped in the circuit of valve 35.