Patent GB-615663-A (GB)
Title: Arrangements for recording time interval between pulses
IPC: G01S7/04
Filed: 1946-03-22
Abstract: 615,663. Electric signalling systems. STANDARD TELEPHONES & CABLES, Ltd. March 22, 1946, No. 8933. Convention date, April 9, 1945. [Class 40 (i)] [Also in Groups XIX and XL (c)] A recorder for use in a pulse radar system consists of one electrode comprising a conducting plate, a second electrode comprising a bar of spaced conducting segments which are coupled to respective tappings on a delay line, and a sheet of voltage-responsive recording paper placed between the electrodes, there being connection points on the first electrode and at each end of the delay line. Pulses derived from the exploring and echo pulses are applied to separate respective connection points, so that, for each echo signal received, there is developed at a point along the second electrode corresponding to the echo time a voltage, equal to the sum of the two pulse voltages, which is sufficient to produce an indication on the recording paper, although the individual pulse voltages are not so sufficient. Fig. 2 illustrates an embodiment of the invention which is employed as a plan-position indicator. Echo pulses from the receiver are applied through slip rings 24 to one end of the delay line 20 which is connected as shown to the bar of conducting segments 17. A pulse which is derived from the transmitter pulse and delayed by the time corresponding to the maximum range to be displayed is applied to a pulse-sensitive relay 27 which is operated to permit a pulse of the desired voltage amplitude to be applied to the counter-electrode 15. A sheet of voltage-sensitive paper 16 is placed between the electrodes 15 and 17. At the instant when the delay voltage pulse is applied to the electrode 15, the echo pulses will have travelled down the delay line 20 so that the signals from zero range will have reached the centre of the display, while signals from maximum range will be at the outermost end of the line. The sum of the two sets of pulses produces a voltage sufficient to cause an indication to be produced, though individually they are insufficient, so that, at the instant of application of the pulse to the plate 15, the system prints, the range of each reflecting object corresponding to the distance of the corresponding indication from the centre of the display. The shaft 22 bearing the electrode 17 rotates with the directive aerial system so that a P.P.I. display is obtained. In alternative embodiments, Fig. 5 (not shown), the echo pulses are applied to the plate 15 while the pulse from the transmitter is applied to the inner end of the line 20 and, Fig. 6 (not shown), the two sets of pulses are applied one to each end of the delay line, the plate 15 being earthed. In a further embodiment, Fig. 9 (not shown), means are provided for drawing a fresh piece of paper between the electrodes after each complete revolution of the aerial system. To overcome difficulties due to distortion and attenuation in the delay line, repeaters may be inserted at intervals, or, Fig. 7 (not .shown), the line may be divided into a plurality of parts which are connected to the receiver through a switch which operates to transfer the received signal from one portion of the line to the next at suitable intervals. Fig. 8 shows a multiple line structure wherein the transmitter pulse is applied to a continuous line 58 to act as a pedestal while pulses at four times the transmitted pulse recurrence frequency generated in circuit 60 are applied to the sections 62, 63, 64, 65. Neither of the sets of pulses is of sufficient amplitude alone to cause the appropriate indications to be made, but together the amplitude is sufficient, so that in only one of the four sections 62, 63, 64, 65 is the output from 60 operative at any one instant.