GB1019796A - Airborne radar system - Google Patents

Abstract

1,019,796. Pulse radar. INTERNATIONAL BUSINESS MACHINES CORPORATION. Dec. 6, 1962, No. 46153/62. Heading H4D. In an airborne pulse radar for terrain avoidance the aerial, relative to the aircraft, is movable in azimuth and fixed in angular elevation, the receiver affords in response to each emitted pulse a group of signals corresponding to the elevation of points of the terrain within a selected range at the corresponding azimuth position, the signal representing the highest elevation (height) of the terrain is extracted from that group, and one pair of co-ordinate deflection means of a display device is energized in response to the extracted signals the other pair of co-ordinate deflection means being energized in accordance with the azimuthal position of the aerial. The angular elevation of echoes is given by the ratio of difference, A, and sum, # signals-in a monopulse arrangement, Fig. -2 (not shown), a computer (22) affording signals representing the difference between the distance Fig. 1, h (not shown); of terrain at range R below the aircraft's (level) flight path and the distance h 0 of a " clearance plane " below the latter, in accordance with the expression: R(γ+K#/#) - h 0 where K is a constant and γ is the depression angle of the monopulse bore-sight axis. The computer output is fed to a capacitative peak detector (26) discharged by a pulse in each radar pulse repetition period, the output voltage from which is proportional to the highest terrain elevation and is fed to the vertical deflection circuits (28) of a direct-view storage tube (29) via an integrator (27) for reducing noise and spurious signals. The predetermined range gate (24) corresponding to range R is selectable. The horizontal deflection circuits (31) are fed from a resolver (32) coupled to the azimuth scan (e.g. 120 degrees) of the aerial. The display afforded, Fig. 3 (not shown), is a line 34 indicative of the height of the clearance plane; an electronic cursor (37) is imposed on the face of the display tube to show the position of the aircraft, together with electronic vertical (35) and horizontal (36) cross-hairs. The apparatus may be added to, Fig. 4 (not shown), to operate an automatic pilot or an instrument " height " needle.