GB590711A - Wave-signal transmitting and receiving system of the radar type - Google Patents

Abstract

590,711. Radio signalling. HAZELTINE CORPORATION. Jan. 29, 1945, No. 2307. Convention date, Feb. 19, 1944. [Class 40 (v)] In a transmitter-receiver system for transmitting pulse signals to a distant point within a given operating distance and receiving back related pulse signals, the receiver is rendered sensitive for an interval following each transmitted pulse not substantially longer than the propagation time to and from the distant point. This mode of operation results in the reduction of noise interference and of interfering radiation if a super-regenerative receiver is employed and enables the receiver to be operated at a higher sensitivity than is possible with continuous operation. The pulse transmitting and receiving system shown, which may be employed to interrogate a responding beacon, comprises the power oscillator 12, pulse modulated by the keying unit 10 and amplifier 11, and the receiver comprising R.F. amplifier 17, super-regenerative stage consisting of valve 19, quench oscillator 29 and diode detector 31, and the modulation signal amplifier 35 and reproducer36. Valve 19 and the diode 31 are normally biassed - off by means of resistors 55 and 50 which are common to the normally conducting valves 48, 47. The gain of the pentode 18 in the R.F. amplifier is also reduced by virtue of the voltage drop in resistor 57. The positive modulating pulses, curve A, from the amplifier 11 are fed to cause valve 40, which is normally biassed-off, to conduct and discharge condenser 43 rapidly. At the end of the pulse, condenser 43 commences to charge up through the variable resistor 45. The waveform B produced at the anode of valve 40 is fed through condenser 49 to the grids of valves 47, 48 which are thereby put off so that the cathode potentials of valves 19 and 31 vary as indicated at C, while the screen voltage of valve 18 varies as indicated at D and raises its transconductance above the average value for steady state operation. The duration t0-t1 of the receptive period is thus controlled by adjustment of the variable resistance 45.