Patent GB-583475-A (GB)
Title: Improvements in or relating to object-locating and -detecting systems
IPC: G01S1/02
Filed: 1943-08-27
Abstract: 583,475. Radiolocation. LAWS, C. A., PUMPHREY, R. J., RATSEY, O. L., WATSON, D. S., and WRIGHT, C. S. Aug. 27, 1943, No. 14058. [Class 40 (v)] A radiolocation or similar pulse-operated object locating system employs a cathode-ray tube indicator provided with two correlated time base traces, one of which displays signals as deflections, while the other presents a series of calibration markers. Means are provided for expanding both traces for a short distance on either side of a selected signal and simultaneously moving a datum calibration mark along the second time base trace into alignment with the selected signal whereby the range of the object giving rise to the signal is indicated by the position of the phaseshifter controlling the movement of the calibration markers. The transmitter pulse recurrence is controlled by a 500- cycle alternator and a synchronizing pulse from the transmitter, which is fired by the first half of each cycle, is applied over lead Q to the time-base circuit V10, Fig. 2, to produce the first trace A, Fig. 1a, on which are displayed the transmitter pulse S and echo signals S1, S2, from the receiver V]. The second half of each alternator cycle causes a valve V5 to produce a 300 microsecond pulse which is applied to two gate valves V7, V16. A crystalcontrolled oscillator V3 produces calibration markers corresponding to 1000 yard intervals which are fed to the gate valve V7, and also through the phase-shifting goniometer G to the gate valve V16. The calibration pulses released from valve V 16 by the 300 microsecond pulse are fed to the Y1 plate of the cathode-ray tube and appear as deflections on the second time-base B which is produced by generator V10 under the control of the first calibration pulse released by gate valve V7. The trace B is thus synchronized with the calibration pulses which appear stationary, but can be continuously shifted across the trace by the goniometer G to bring a selected pulse M1 into alignment with any portion of the first trace A. The sweep voltages for traces A and B which are fed from circuit V10 to the X2 plate of the cathode-ray tube are also fed to the valve V12 which develops a high-speed time-base or accelerating voltage, at a moment in the duration of traces A and B determined by the setting of tapping T on potential divider P, which is fed to plate X1 to speed up traces A and B over a selected section embracing a range of approximately 1000 yards. The goniometer G and potential divider Pare mounted on a common shaft S and the potential divider is so graded that the calibration pulses and the expanded sections move over the time base traces in step, and when the datum calibration mark M1 is aligned with a selected signal, such as S2 in the expanded section, the position of pointer N on dial D, which indicates the degree of rotation of the goniometer, is a measure of the range of the selected echo signal. Detailed operation of circuits.-Fig. 3. Sine waves at 164 kc/s. from the output circuit L4, C12, C13 of the crystal oscillator V3 are fed in part through condenser C16 and cathode follower valve V6 to the control grid of the gate valve V7 and in part through lead LA and an amplifier V14 to the field coils F1, F2 of the phasing goniometer G. A transformer T3 in the cathode circuit of valve V14 gives a balanced output which is fed through phasing resistances R54-R57 and condensers C44, C45 to the earthed centre-tapped field coils F1, F2 which thus carry equal currents in quadrature. The output from one half of the rotary coil R, which is continuously variable in phase with respect to the input in dependence upon the angle and direction through which coil R is rotated, is fed through a shaping amplifier V15 to the control grid of the gate valve V16. The 500 c/s. output from the alternator (not shown) is fed to the grid of a squaring valve V4 producing a square pulse during the second half of each cycle, which is differentiated by condenser C15 and resistance R12 and applied to valve V5 which gives in response a positive square pulse output of approximately 300 microseconds duration. This pulse is fed through condenser C20 to the suppressor grid of gate valve V7, and through condenser C19 and lead LB to the suppressor grid of gate valve V16, to allow calibration markers to be fed through condenser C42 to the Y1 plate of the cathode-ray tube and appear on the B timebase trace. The time-base generating circuit comprises a relaxation relay V9, V10, the anode of valve V9 and control grid of valve V10 being coupled by condenser-resistance combination C26, R34, the time constant of which determines the duration of the time-base traces, and the screen grid of V10 being coupled to the control grid of V9. The relaxation relay is triggered via a valve V8 by the synchronizing pulse from the transmitter applied to the control grid of V8 during the first half of each alternator cycle, or by the first calibration pulse from gate valve V7 applied to the cathode of valve V8 during the second half of each alternator cycle. When triggered, the relay generates a 300 microsecond positive square wave on the screen grid of valve V10 which is fed through condenser C27 and lead LD to brighten the trace on the cathode-ray tube, a diode V17 limiting the amplitude of the pulse. Simultaneously, the anode current of valve V10 is cut off and condenser C29 charges up through resistance R35 to generate the sweep voltage which is applied to the X2 plate of the cathode-ray tube. To generate the high-speed time-base, the sweep voltage is applied through a cathode follower V11 to the control grid of a valve V12 which is provided with a floating H.T. supply F, connected to the tapping T on the potential divider P. The potential divider has an exponential potential gradient similar to that developed by the condenser C29 and at an instant in the time-base sweep determined by the setting of the tapping T, valve V12 is rendered conducting, the anode voltage falling sharply in about 6 microseconds and thereafter remaining stationary until the end of the timebase sweep. This voltage is fed through condenser C30 to the X1 plate of the cathode-ray tube to produce the expanded sections of the time-base sweeps. Variable resistances R72, R74 in series with the potential divider P enable the rate of movement of the expanded section or high-speed time-base and its zero position to be adjusted to 'agree with the movement of the calibration markers and the range-indicating scale. Incoming echo signals are fed to a video amplifier VI, through a delay network DN in order to bring the transmitted pulse within the field of the A time-base trace. Amplified signals are fed to the Y2 plate of the cathoderay tube via a condenser C6, a D.C. restoring diode V2 being provided. In a modified circuit for producing the highspeed time-base, Fig. 3a (not shown), which does not require a floating H.T. supply, a double triode relaxation relay with a common cathode impedance which carries a large negative bias, and coupling from one anode to the other grid, has the time-base sweep voltage applied to one grid and the voltage from the potential divider, applied to the other grid. When the grid voltages acquire a predetermined relative value, the relay is triggered and renders a valve conducting which discharges a condenser to produce the accelerating voltage wave for application to the X1 plate of the cathode-ray tube.