Patent GB-748110-A (GB)
Title: Improvements in or relating to radar systems
Inventor: PLAISTOWE DONALD LEOPOLD
IPC: G01S13/87
Filed: 1954-01-08
Abstract: 748,110. Photo-electric pulse generators. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Nov. 25, 1954 [Jan. 8, 1954], No. 593/54. Class 40 (3). [Also in Group XL (c)] A radar system comprises a plurality of high-frequency transmitters each radiating a vertical fan beam covering adjacent vertical sections of the field of interest and a receiver arrangement capable of selectively routing echo signals derived from different transmissions via objects at different heights to a display representing such objects in azimuth and elevation. There may be five transmitting magnetrons or klystrons 18, 19, 20, 21 and 22 transmitting in sequence. A " line scan " oscillator 2 controlling them triggers saw-tooth generator 4 whose output is applied to cause the beam of cathode-ray tube 5 to scan in the direction l. A line of photo-transistors 8, 9, 10, 11 and 12 are mounted on the fluorescent screen of the tube and the scanning causes them to give triggering outputs in turn to pulse generators 13 to 17, each of which controls a respective one of the transmitters 18 to 22. Energy from each of the transmitters is fed over branched waveguide paths to two radiating horns and that radiated. by the horns 23 to 27 passes through corresponding cylindrical lenses 33 to 37 to illuminate the field of interest in a series of adjacent sequential vertical fan beams. Associated with each transmitter there is a set of mixers mixing the signals derived from one of the transmitters through one of the lower set of horns 28 to 32 and the corresponding echo signals. Considering only the transmitter 22 and its associated equipment signals from horn 32 are directed by one of two mirrors 47 to illuminate all of crystal mixers 52a to 52e. Received echo signals from the part of the area illuminated by the radiation from horn 27 and lens 37 pass through spherical lens 42 and are directed by the other of the mirrors 47 selectively to one or other of the crystals 52a to 52e. The crystal energized in any instance depending on the elevation of the object causing the echo signal. Each crystal is coupled through its own amplifier (53a to 53e) to its own gate circuit (54a to 54e). The gate circuits are normally closed and all of them, including those associated with the other transmitters, have their outputs joined to feed the intensity control electrode of display tube 7. The gate circuits are opened in accordance with the scan operation of tube 6. The beam of this tube is moved in the direction indicated at l in accordance with the sawtooth waveform from unit 4 and the scan is also stepped across the tube. For this purpose " frame scan " oscillator 1 is arranged to feed multivibrator 57 and 58 producing pulses at 5 times the frame frequency which are passed through rectifier 63 to discharge condenser 61 in steps as indicated on the drawing. The condenser is returned to its original voltage level after each set of 5 steps by a pulse direct from oscillator 1 through amplifier 59 and diode 60. The stepped waveform produced is inverted by amplifier 64 and fed to the horizontal deflection coils 65 of tube 6. It is arranged that there are ten line scans in succession in each position of the beam across the tube and each of these opens in turn the gates associated with each transmitter corresponding to a given elevation. The beam of tube 6 performs its gate-opening function by being moved over a pattern of photo transistors on the tube face adjacent the screen, each of transistors being coupled to the appropriate gate circuit through a pulse generator. The display tube 7 is scanned in orthezonal directions by line and frame scan frequency sawtooth waveforms and its beam is brightened by the signals fed to it from the gate circuits to give an azimuth and elevation display. This display will contain 10 adjacent line scans for each elevation sub-range.