Patent GB-585910-A (GB)
Abstract: 585,910. Radiolocation. WHITE, E. L. C. March 18, 1940, No. 5027. [Class 40 (v)] Recurrent pulses of high-frequency oscillations are fed to a super-regenerative receiver and the super-regenerative cycle is initiated when the pulses are present. The transmitting apparatus comprises a pulse generator 1, modulator 2, transmitter 3 and transmitting aerial 4. The transmitter 3 may operate at 3000 megacycles per second and the pulse generator 1 may generate pulses 0.2 microsecond in duration at intervals of 50 microseconds. After reflection by an aircraft or other object, the pulses return and are received on an aerial- 5, which may be a dipole aerial tuned to 3000 megacycles per second and arranged within a parabolic reflector. The receiver comprises a super-regeneration valve 6 and a rectifying diode 7. In the anode circuit of the valve 6 is a circuit comprising an inductance 8 and condenser 9 tuned to 3000 megacycles per second. An inductance 10 is connected in series with a condenser 11 in the grid circuit ot the valve 6, and is coupled with the inductance 8 so as to cause the valve 6 to oscillate when a suitable bias potential is applied to its grid. The grid is periodically biassed positively via a resistance 12 connected to a time delay network 13 which is fed with pulses by the pulse generator 1. The network 13 may be varied so as to vary the timing of the initiation of the oscillations of the valve 6. The inductance 8 is also coupled to an inductance 14, across which is connected the diode 7 having an output circuit comprising an inductance 15 and resistance 16 shunted by a condenser 17. The aerial 5 is connected to a tapping on the inductance 14, one end of which is earthed. The circuit is so arranged that in the absence of reflected signals the oscillations developed by the valve 6 when in the superregenerative state do not reach saturation, but preferably reach only between one-tenth and one-third of the saturation amplitude during a pulse applied to the grid of the valve 6. On the arrival of a reflected signal, the amplitude of the oscillations developed increases.. The oscillations are fed to the diode 7 through the coupling between the inductances 8, 14 and a rectified signal corresponding to the envelope wave-form of the received signals appears across the resistance 16 and may be amplified by means of a succeeding modulation frequency amplifier. The delay network 13 is varied until the timing of the initiation of the superregenerative cycle corresponds with the arrival of the reflected pulse, which is indicated by the output of the diode 7 increasing to a maximum. The relative timing of the transmitted pulses and the reflected pulse may then be determined from the time delay introduced into the network 13 and the distance of the reflecting object deduced therefrom. The timing of the initiation of the'super-regenerative cycle may be varied cyclically over a time period long in relation to the 50 microseconds intervals and the output obtained from the rectified signal is applied to one pair of deflecting plates of a cathode-ray oscillograph, a saw-tooth waveform having a periodic time equal to the time period of the cyclic variation being applied to the other pair of deflecting plates. The valve 6 may be replaced by a magnetron or a Klystron oscillator. The oscillator may be incorporated in the transmitter 3 by means of switching circuits so that it is used alternately for generating the signals to be radiated and for receiving the reflected signals, and may be arranged to develop more power when transmitting than when receiving. The rectified signals received during a number of super-regenerative cycles may be integrated in a storage device so as to reduce the'effect of random noise as described in Specification 577,275. The azimuth and elevation bearing of the object may be determined by measuring the difference in timing between the signals received on a number of spaced aerials as described in Specifications 581,920 and 585,908. A single receiver may be connected to each of the aerials in turn, as described in Specification 585,909. Specification 585,907 also is referred to.