GB593467A - Arrangements for transmitting and receiving short electric pulses - Google Patents

Abstract

593,467. Radiolocation ; valve circuits. STANDARD TELEPHONES & CABLES, Ltd. July 20, 1944, No. 13949. Convention date, Jan. 23, 1943. [Class 40 (v)] In a combined pulse transmitting and receiving arrangement such as a radiolocation system, the transmitter and receiver are energized with raw alternating voltage of a period long compared with the periods during which pulses may be received, and the phase of the voltage energizing the receiver is variable with respect to that energizing the transmitter. A radiolocation system, Fig. 1, comprises an R.F. oscillator 8, modulating pulse generator 9 and aerial 10 ; a receiver 11 feeding a cathode-ray indicator 12, the sweep generator 14 for which is controlled by the pulse generator 9. A device 13 is provided to block the transmitter during the emission of pulses and a reference pulse delay device 15 provides a movable reference pulse 16 which may be adjusted to coincidence with an echo 17 on the oscillograph screen, for range determination. An A.C. source 18 provides energization directly to the transmitter elements 8 and 9 and through a phase-shifter 19 to the receiver 11, oscillograph 12 and sweep generator 14..Pulse generator 9 may be of the spark type or be a blocking oscillator, Fig. 3 (not shown), producing a pulse 20 at a definite point in the cycle of A..C. anode supply as shown in Fig. 2. The maximum operating period t<1>, during which an echo may be received corresponding with the duration of the sweep voltage 21 synchronized by the pulse 20, should occur at the peak portion of the A.C. wave as indicated at A<1>-B<1> where the variation in voltage is small. If the transmitted pulse occurs at a position such as 20a, the interval A<2>-B<2> corresponding to the sweep 21a has a large variation in voltage so that by means of phase changer 19 the A.C. wave fed to the receiving equipment is retarded by an amount # in order that the peak period A<3>-B<3> may be employed. A portion of the range A-B may be displayed on an expanded scale by the insertion of a device 22 which delays the commencement of the time base sweep which is increased in speed, the phase changer 19 being adjusted to bring the operating interval to the positive peak of the A.C. wave. The transmitted pulse may be generated at any desired point on the A.C. wave by an arrangement, Fig. 4 (not shown), which limits and differentiates the wave to produce sharp pulses, the positive pulses being selected and fed through an adjustable time delay device to control the pulse generator 9. Fig. 5 and 6 (not shown). illustrate resistance-capacity and direct coupled amplifiers which operate with A.C. anode supply, the time constants of the R-C coupling circuits being designed to filter out low frequencies such as that of the energizing source. Fig. 7 (not shown) illustrates an A.C. supply to a cathode-ray oscillograph. The sections of the voltage divider feeding the various electrodes are arranged with no byepass condensers, or with condensers associated with each section to produce similar time constants.