GB744640A - Improvements in or relating to radar display systems - Google Patents

Abstract

744,640. Radar displays. DECCA RECORD CO., Ltd. June 29, 1954 [June 29, 1953], No. 18029/53. Class 40 (7). In a radial scan P.P.I. display for a radar system wherein the cathode-ray tube beam is deflected by fixed deflector coils means are provided for feeding additional scanning signals into the deflector coil system during intervals between the regular recurrent radar scans to produce a bearing marker trace. This marker may be positioned manually to coincide with a bearing direction to be determined and the bearing then read from the setting of the control element. It is desirable that one set of timebase generators should be used for both the production of the display trace and the marker trace although if the quiescent time between the display traces is less than the time taken for a display trace the bearing marker scan will require to be performed at a higher speed than the display trace. In a system according to the present invention it is possible to off-centre the display and bearing marker traces independently. In a preferred embodiment four fixed scanning coils 10, 11, 12 and 13 are arranged in two pairs as shown for deflecting the cathoderay tube beam. They are energized respectively from the separate time-base generator circuits 14, 15, 16 and 17. The aerial is coupled to drive magslip 18 which produces two outputs proportional respectively to the sine and cosine of the' angular position (#) of the antenna. These output voltages Va Sin # and Va Cos # are applied to differential voltage units 19, 20, 23, 24, as indicated to give potentials of V 1 - Va sin #, V<SP>1</SP> + Va sin #, V<SP>1</SP>- Va cos 0 and V 1 + Va cos # which are fed over switches 21, 22, 25 and 26 to respective ones of the timebase generators. There is also provided a second magslip 30 similar to the first which is manually adjustable and provided with a calibrated scale 31. The outputs from this magslip are fed through a second set of differential voltage units 32, 33, 34 and 35 to switches 22, 22, 25 and 26. The set of switches is operated in synchronism under the influence of pulse gate generator 36 to feed the potentials derived from the aerial magslip to the time-base generators to produce the display scans and to feed the potentials derived from magslip 30 to the timebase generators to produce the bearing marker scan between the display scan traces. A suitable time-base generator circuit is described with reference to Fig. 2 (not shown). Specifications 679,722, 679,723 and 737,519 are referred to.