Patent GB-1113021-A (GB)
Title: A moving target electromagnetic detection system
IPC: G01S13/64
Filed: 1965-04-15
Abstract: 1,113,021. Pulse doppler radar. STANDARD TELEPHONES & CABLES Ltd. (Laboratoire Central de Telecommunications). 15 April, 1965, No. 16171/65. Addition to 1,103,510. Heading H4D. The detection system of the parent Specification is modified for when the antenna scans in an oscillatory manner through an angle in azimuth, such that targets in one range increment are displayed as a B-type display when the antenna scans in one direction and the display switches from said one range increment to the next when the antenna reverses its direction of scan. The modification is brought about by changing the control pulse generator GE, Fig. 1, to the circuit of Fig. 2, which circuit involves waveforms shown in Fig. 3. In Fig. 2 a generator 1 produces a pulse train IE in synchronism with and having the same repetition rate F as the transmitted pulses and which causes a three-phase generator 2 to generate three corresponding sine waves which are fed to a synchrotransmitter 3 having a rotor producing a single sine wave with a phase dependent on the position of the rotor. This sine wave is fed to a stepped delay line comprising several sections, each section giving a delay corresponding to the chosen range increment, a section being added to the circuit each time the antenna reverses direction. The thus delayed sine wave produces a corresponding pulse train each pulse of which triggers a monostable circuit 6 to produce a gating pulse 16 having a width corresponding to the range increment and delayed from the corresponding IE pulse by the delay introduced by synchrotransmitter 3 and the number of incremental delays introduced by delay 4. Synchrotransmitter 3 thus determines the lowest range displayed. Oscillator 7 and pulse generator 8 produce a pulse train 18 of frequency Kn(F + f1), where K is the number of range increments to be investigated, or in the number of channels used (e.g. 5 in Fig. 1), and f1 is a frequency small compared with F. Train 18 is fed to gates P11 and P12 and also to a divider 9 to produce a pulse train 19 of frequency K(F + f1). This last pulse train produces pulse train 1M11 from monostable circuit M11 1 which is fed to gate P11, to gate through pulses 1P11 from the train 18. These pulses could stroke through the entire range, but are limited to the range increment being displayed, by being gated through gate P12 by means of gating pulse 16. The gated pulse is itself connected to a gating pulse 1M12 by monostable circuit M12 which is used to gate through a pulse from train 18 in gate P13, to produce the final control pulse 1P13 for application to the two gates in the channel V1. The circuits C2-C5 for producing the control pulses for channel V2-V6 are similar to circuit C1, first described except that they are fed with the output of the first gate, P11 on P21 &c., of the preceding circuit. The stepped delay 4 comprises five identical L/C sections connected in series and having their outputs tapped and brought out in parallel via individual gates opened in sequence by the movement of the antenna to the limit of its scanning movement. The opening of the gates is controlled by a stepping switch, controlled in turn by relays actuated by said movement of the antenna. The incremental displays may be stacked on the display screen to provide a composite display as in Fig. 5 the direction of the arrows showing the corresponding direction of motion of the antenna.