Patent GB-624600-A (GB)
Title: Improvements in or relating to radio navigational systems
IPC: G01S13/76
Filed: 1945-04-19
Abstract: 624,600. Automatic control systems. JONES, F. E., ROBERTS, W. L., HARRISON, F., UTTLEY, A. M., and WILLIAMS, F. C. April 19, 1945, No. 32029/47. Divided out of 624,558, [Group, XL (c)]. [Class 38 (iv)] [Also in Group XL (c)] A circuit arrangement for determining the rate of change in timing of a recurrent input signal comprises means for progressively varying a locally generated recurrent signal of similar recurrence frequency at a constant rate until the two signals co-exist for at least part of their duration, whereupon the rate of variation of the timing of the locally generated signal is made dependent on the rate of variation of the input signal and a voltage is developed representative of the rate of variation. The invention is described in connection with the radio-navigation system of Specification 624,558 of which it forms a part and the circuit embodiment of the present invention forms the part of Fig. 1 shown. The recurrent input signal is applied to this circuit at T6 and and the locally generated signal of similar recurrence frequency is applied through R76 to the supressor grid of V15. This valve forms part of a delay circuit operating as described in Specification 582,758, [Group XL], to produce a waveform depending in length upon the cathode potential of diode V16 which is fed to the control grid of normally biassed-off valve V17. The anode load of V17 includes a shortcircuited delay network having a ¢Á sec. delay, the resultant anode waveform thus consisting of a 1Á sec. negative going pulse at the beginning and a 1Á sec. positive going pulse a the end of the input waveform. The positive going delayed pulse may be fed through V12 and T9 to a cathode-ray tube indicator scanned at the repetition frequency and fed with the original recurrent signal to show the relationship between the two signals. S4, except when adjusting the apparatus, is on contact 2 and if switch S2 is on contact 2 the control grid of V14 is connected to the junction of R64 and R65 and its potential is dependent on S1 and potentiometer R67. This latter is adjusted so that when there is 165 volts on S1 (position 3) there is no current flow to or from C26 and there is no variation in the locally-generated pulse timing. For other voltages on S1 the local pulse timing will increase or decrease, causing the cathode-ray indication to move along the time base. With S2 on position 3 the potentiometer R75 can be used to manually adjust the local pulses into partial coincidence with the input signals. When the two sets of signals coincide and with S2 on contact 2 and S1 on contact 2 the local signals will follow the input signal variations. To produce this action the input pulses from T6 cut off V10 to produce a positive pulse at the anode of V11. This valve is normally cut off, but the positive delayed pulses from V17 removes its bias and consequently current is drawn through R61 proportional to the time of overlap of the input and local pulses. This current is smoothed so that the average voltage drop across R61 determines the potential of the grid of V13 which is a D.C. amplifier. The anode voltage of V13 which varies between 15 and 350 volts according to the degree of overlap is fed to V14 to cause a variation in the timing of the locally generated signals such as to maintain a condition of partial overlap. Under these conditions the anode voltage of V13 is proportional to the rate of variation of the input signal and may be obtained from T7.