GB638278A - Improvements in and relating to radar systems - Google Patents

Abstract

638,278. Radiolocation. MINISTER OF SUPPLY. Dec. 18, 1946, No. 37257. [Class 40(vii)] A radar system transmits uniformly recurrent groups of pulses or pulse combinations and co-operates with receiving means adapted to receive echo pulses resulting from each pulse or pulse combination of a group, a plurality of displays separately displaying echoes within different predetermined range-bands being associated with the receiving means and the echo pulses being directed to be displayed on the display appropriate to the range-band within which the echo pulse lies. The system permits a radar operating up to long ranges to have a high pulse recurrence frequency. In Fig. 1, independent radars 1-5 each transmit on the same radio frequency at 1000 pulses. per second and operate in rotation at 200 Á sec. intervals, whereby an effective pulse repetition rate of 5000 per second is obtained. Associated with the radars are five displays 11-15 and five rotary beam electronic switches 16-20. The switches move anticlockwise one step every 200 Á sec. to connect each display in turn to each radar receiver. Display 15 is connected to each receiver for the first 200 Á sec. after the corresponding transmitter has pulsed and shows echoes up to approximately 20 miles. Similarly, displays 14, 13, 12, 11 are connected to the receivers for the periods 200-400, 400-600, 600-800, 800-1000 sec. respectively indicating the approximate range bands of 20-40, 40-60, 60-80 and 80-100 miles. Each echo appears on the appropriate display 5000 times per second although the individual radars operate, at 1000 per second. As an alternative to five separate aerials 6-10, one wide-band aerial may be employed with each pulse at a different radio frequency. Fig. 3 (not shown) illustrates a suitable receiver for such a system employing five narrow-band filters to separate the signals. Alternatively, each of five receivers may be connected permanently to one of five displays, the local oscillator frequencies being changed-appropriately by a suitable switching system. A further embodiment, Fig. 4 (not shown), employs a common radio frequency and transmits pairs of pulses at five different spacings. Coincidence circuits responsive to particular spacings separate the received signals. The displays corresponding to the different range bands may appear separately as shown in Fig. 1, or appear on a common multi-beam cathode-ray tube. Alternatively, the displays may be superimposed. optically.