Patent GB-991207-A (GB)
Title: Three dimensional display system
IPC: G01S7/20
Filed: 1962-11-01
Abstract: 991,207. Radar display; cathode-ray tube circuits. MARSON ELECTRONICS CORPORATION. Nov. 1, 1962 [Nov. 6, 1960], No. 41427/62. Headings H4D and H4T. A radar target display system comprises an indicator tube, Fig. 1, having a radial sweep, said sweep having a first portion (inner) and a second portion (outer), first input means supplying a first signal pulse to the first sweep portion to indicate the range P of the target, the angular position of the sweep being controlled to indicate the bearing O of the target, second input means supplying a second signal pulse to the second sweep portion to indicate the altitude H of the target, means to store the second signal during the first portion of the sweep and to apply the second signal to the indicator tube during the second sweep portion, and means controlling the first and second signal pulses to display the target position only if the altitude of the target is within a preselected range. In the arrangement shown a train of pulses (waveform D, Fig. 3) having heights proportional to the altitudes of the targets is produced by a height finding radar, and fed to an altitude layer processor 12, Fig. 2, which only lots pass those pulses having heights representing altitudes within the selected range H 1 -H 2  as determined by the threshold and width analogue voltages chosen by switches SIC and SID respectively. The selected pulse (waveform H) is passed to an OR gate 11 for display on a P.P.I. C.R.T. indicator 1. The sweep voltage of the indicator (waveform A) is passed to a comparator 2, together with a voltage representing 4/5R on the radius of the inner sweep portion, such that the comparator delivers a step voltage (waveform C) when the two voltages are equal. The indicator sweep voltage is also supplied to a feedback amplifier 6, together with one of various biasing voltages V1-V5 to produce a shifted sweep voltage that bears the same altitude/voltage relationship as the pulse in train " H " (waveform D) and reaches a voltage representative of altitude H, when the indicator sweep has reached 4/5R. The step voltage from comparator 2 is applied to driver 3 which produces control voltages switching gate 4 from off to on and gate 5 from on to off. Train "H" is applied to gate 5 and the shifted sweep voltage from amplifier 6 is applied to gate 4. The combined outputs of the two gates (waveform F) is applied via a video amplifier 8, to the vertical deflection plates of a C.R.T. type storage tube 7. A voltage from driver 3 causes the storage tube to write during the first sweep portion and destructively read out during the second sweep portion. The storage tube scanning beam is intensified in synchronism with the deflecting voltages from the amplifier 8 by a pulse train " A " (waveform E) coincident with pulse train "H" but of constant height which is passed through a differentiator 16 to select the leading edges of the pulses, a delay 17 to shift the leading edges to intensify a selected part of the corresponding " H " pulses, and a blocking oscillator 18 to extend the duration of the intensifying pulses. A rectangular pulse coincident with the sweep voltage in the deflecting voltage, is added to the above intensifying pulses, from driver 3 via OR gate 9. The arrangement is such that spots are " written " on the storage tube screen, during the first portion of the sweep period, in vertical positions corresponding to the targets altitudes and those representing altitudes within the selected range are destructively read out to a video amplifier 10 during the second portion of the sweep period for display on the C.R.T. indicator via OR gate 11. The shifted sweep voltage from amplifier 6 is compared with a height cursor reference voltage in comparator 13 to give a reference pulse for display on the C.R.T. indicator via OR gate 11. Since the screen is nominally scanned along one line only, damage of the screen along the said line is prevented by the provision of a small low frequency horizontal deflecting voltage from oscillator 14, which causes the beam to scan the screen along a sinusoidal track, the amplitude of the said track being less than a spot diameter. A high frequency horizontal deflection voltage is also provided from oscillator 15 to broaden the read-out pot into an oval to overcome any possible misregistering of the write and read scans. When it is desired to monitor all the height ranges simultaneously, duplicate sets of equipment may be used. Specification 971,561 is referred to.