GB618499A - Improvements in or relating to arrangements for locating obstacles by electromagnetic waves - Google Patents

Abstract

618,499. Radiolocation; pulse circuits. STANDARD TELEPHONES & CABLES, Ltd., CHATTERJEA, P. K., and HOUGHTON, L. W. May 25, 1945, No. 13201. Addition to 586,833. [Classes 40 (vi) and 40 (vii)] In a radiolocation system as described in the parent Specification, in which a pulse-generating saw-tooth oscillator is synchronized by the reflected pulses so that the pulse-recurrence frequency is a measure of the distance to the reflecting object, faulty operation by reflected pulses from objects beyond the range for which the system is designed, i.e. at distances greater than that corresponding to the maximum pulserecurrence frequency provided by the oscillator circuits, is prevented by biassing the grid of the oscillator, which is of the gas-filled type, by a potential obtained by rectifying the sawtooth output. In the system shown, the output of the gas-filled triode 11 is fed to a valve 23 which constitutes the first valve of the pulse generator and may be of the overload type. The storage condenser for the relaxation circuit comprises a condenser 15 fed through a resistance 16 and the time constant of the circuit for a given grid bias determines the maximum range of the system. A diode 28 with a load resistance 21 and storage condenser 29 is arranged across the tube 11, and the rectified output is applied to the range meter 9 and to the grid of the tube 11. The bias thus applied to tube 11 varies inversely with the anode potential so that it has a small value, which can be overcome by echo pulses, just before the tube is due to fire, but has a large value after the tube has fired so that echo pulses arriving from objects beyond the maximum range are unable, due to this bias and to their relatively-small amplitude, to fire it again.