Patent GB-665442-A (GB)
Title: Improvements in or relating to time indicating and measuring apparatus for use in radar and other radio echo systems
IPC: G01S1/72
Filed: 1946-09-10
Abstract: 665,442. Radiolocation; pulse generating circuits. COMPAGNIE GENERALE DE TELEGRAPHIE SANS FIL. Sept. 10, 1946 [May 7, 1942], No. 27224/46. Classes 40 (vi) and 40 (vii). In a pulsed radar system in which measurement of the echo time is effected by observing the phase shift necessary to bring a reference signal into successive coincidence with the transmitted pulses and the received echo signal the reference signal is a short signal of such form as to produce, on the screen of the display cathode-ray tube, a trace having a sharp discontinuity whereby it may be brought into precise coincidence with the beginning of an echo signal. The reference signal, which may be a voltage wave of the form shown in Fig. 3, has a negative peak q and a positive peak r and is produced by any known means such, e.g., as the circuit of Fig. 1, by applying to the input terminals a, b a sinusoidal voltage u, the period of which is equal to the interval of time separating two successive transmitted pulses and the phase of which may be varied by calibrated means, not shown. The reference signal thus produced, which may have a duration of about <SP>1</SP>/ 10  micro-second, is applied to the intensity control electrode 14 of the cathode-ray display tube and produces a trace consisting of a shadowy zone q<SP>1</SP> followed by a luminous spot r<SP>1</SP> (Fig. 4a), the zone q<SP>1</SP> being caused by the negative peak q and the spot r<SP>1</SP> by the positive peak r (Fig. 2). In this trace the edge s<SP>1</SP> of the luminous spot is sharply defined and may easily be brought into precise coincidence with the commencement of a transmitted or received signal, e.g. the signal a, b, c, d, Fig. 4 (b). In an alternative arrangement the reference signal of Fig. 3 is applied to one of the vertical deflection plates of the display tube, Figs. 5 and 6 (not shown). In a further alternative arrangement, two 180 degree phase-opposed reference signals of the type shown in Fig. 3 are applied to opposite vertical deflection plates, Fig. 7 (not shown). The Specification as open to inspection under Sect. 91 includes the following subject-matter: (a) An arrangement in which the deflection of the scanning spot on the screen of the display cathode-ray tube is effected at constant linear speed for both the trace and retrace periods, which are separated on the screen so that both are available for observing an echo signal. In the described arrangement a trace of the type shown in Fig. 13 (Cancelled), is produced by applying a triangular wave, Fig. 10 (Cancelled), having a period t/n, where t is the period of the oscillator from which the transmitted pulses are derived, to the horizontal deflection means of the display tube and a saw-tooth wave, Fig. 12 (Cancelled), of period t to the vertical deflection means. (b) An arrangement in which a variable strobe pulse is produced from the master oscillator which controls the pulse generator of a radar transmitter by means of a multi-phase generator controlled by the master oscillator and which supplies, via a rotatable search coil device, a voltage of adjustable phase (relative to that of the master oscillator) to control a second pulse generator producing the strobe pulses, Fig. 3 (Cancelled, not shown). Fig. 4 (Cancelled) shows details of this arrangement and includes a master oscillator O, the output of which is split into two parts by means of transformer 4, one part being fed to a pulse generator G1 comprising valves 8 and 12, the pulses produced by which are supplied to a modulating stage 15 to control a magnetron transmitter 16 and the other part being fed to a phase splitter producing two waves of 90 degrees relative phase which feed two pairs of fixed coils 25, 26 arranged at 90 degrees to each other and in the " centre " of which is a rotatable coil 27, the voltage induced in which controls the production of the strobe pulses in generator G2. Fig. 5 (Cancelled) shows an arrangement employing a single valve 15 producing two waves of 90 degrees relative phase from a sinusoidal input which may replace the phase splitter T of Fig. 4 (Cancelled). This subjectmatter does not appear in the Specification as accepted.