Patent GB-604592-A (GB)
Title: Improvements in or relating to radio-location apparatus
IPC: G01S7/18
Filed: 1945-03-24
Abstract: 604,592. Radiolocation. LEWIS, W. B., and CARTER, R. H. A. March 24, 1945, No. 7512. [Class 40 (vii)] In a pulse radar system comprising a directive transmitting system whose directivity is continuously varied in the vertical plane, and wherein the echo signals are displayed as intensity modulations of a linear time-base measuring range on the screen of a cathode ray tube, the time base is displaced bodily in a direction transverse to its length in accordance with the variation of the elevation angle of directivity, and a further intensity modulation is applied to the cathode ray tube to provide an adjustable range marker. In Fig. 1 which illustrates a system in which the invention may be employed, the exploring wave is transmitted from an aerial 19 and received by an aerial system 10 the directivity of which is continuously varied between the limits a and b and may also be rotated in azimuth. The aerial system 10 is coupled by a shaft 22 to a potentiometer 23, the output of which varies in accordance with the movement of the aerial and is applied to the vertical deflecting plates of the cathode ray tube. In a further system, Fig. 2 (not shown) a common receiving and transmitting directive aerial array is used, the directivity being varied by varying the phasing of the current in the various elements of the array. The variable phasing unit is driven by an electric motor which also drives a potentiometer system similar to that of Fig. 1 but in this instance arranged to provide a balanced output. In another system, Fig. 4 (not shown) rapid scanning is effected over a narrow band, the mean elevation of the band being varied at a lesser rate. By means of variable inductive couplings, controlled by the rapid and slow scanning means respectively, A.C. voltages having correspondingly varying amplitudes are obtained and are compounded in a device which causes the rotation of a shaft 22, Fig. 3, in accordance with the movement of the beam. A corresponding voltage is induced in winding 35 and this is rectified, smoothed and amplified (if necessary) and applied to the cathode ray tube as before. Fig. 6 illustrates the various marker indications which may be obtained in accordance with the invention by use of the embodiment shown in Fig. 8. Pulses generated at 18 control the operation of the transmitter and of the time-base circuit 21 as previously shown in Fig. 1. The circuit 18 also drives a multivibrator 46, which produces square pulses the length of which may be varied by a potentiometer (not shown). The output of circuit 49 comprises a negative going pulse, corresponding to the trailing edge of the multivibrator pulse, which may be applied direct through condenser 50 to the cathode of the cathode ray tube whereby a variable range marker as shown at 42 is obtained, but, as shown, is applied through stud contacts 51. These contacts are only made at certain elevations of the beam so that an indication 43 occurring, for example, at each unit of elevation angle, is obtained. The pulse from circuit 49 is also delayed by circuit 54 and lengthened by circuit 55. At a certain elevation of the beam, determined by the switch contact 57 under the control of calibrated knob 58 the pulse will be passed to the cathode ray tube where it will produce a variable elevation marker 44. A remote indication of the setting of knob 58 is controlled over line 61 by the switch 59, each contact of which carries a potential representative of its corresponding elevation angle. Since altitude is a unique function of range and elevation angle, a grid may be drawn on the screen of the cathode ray tube giving lines of constant height, Fig. 5 (not shown).