Improvements in or relating to displays for radar and like systems

摘要

841,361. Radar. MINISTER OF SUPPLY. June 12, 1957 [June 13, 1956], No 18242/56. Class 40(7). A reference grid is superimposed upon the display on a P.P.I. radar screen by brightening parts of the rotating line time-base. An alternating generator 6, driven from the aerial shaft 1 through gearing 2, 3, and a selsyn 5, produces a sine wave which is fed to a peaking circuit and converted to a substantially square wave which is then differentiated. The positive pulses of the resultant waveform are used to trigger a monostable flip-flop. The output of this flip-flop is of adjustable duration and may be used to brighten one or more of the line time-bases. By feeding the output to a gate circuit which is opened and shut by pulses spaced at the time equivalent of, say, 2 miles the line time bases will be brightened at every 2 miles spacing giving dotted radial lines. To obtain range circles on the screen in addition to the dotted radial lines, Fig. 2 (not shown), the signal at terminal 12 is passed to a mixer circuit which is also fed with pulses from a 10 mile (equivalent) pulse source. The output at terminal 15 comprises the complete reference grid. The number of radial lines depends upon the frequency chosen for the waveform generator 6. By virtue of the relation of the grid to the line time-base, the origin of the display and the origin of the grid are, of necessity, in alignment.