Equipment for display of a terrain portion on board of vehicles, particularly aircraft

Abstract

Abstract 1. A device for displaying of a portion of terrain on board of vehicles, in particular aircraft (1) moving in relation to the ground, wherein a linear array antenna (A) sharply focussed in azimuth and covering a large elevation angle range, to successively scan in azimuth the portion of terrain to be surveyed, when pivotted azimuthally. where, at each azimuth angle, from the angle range illuminated by the vertical polar diagram, the land supplies a mixture of echo signals which differ both in respect of transit time, proportional to the range of the respective reflecting land element, and also in respect of Doppler frequency fd , to obey the equation : fd = fdmax alpha . cos epsilon = (2vH alpha / lambda ) . cos epsilon ; where vH epsilon is the (air)craft speed in the direction of the azimuth section ; lambda is the radar wavelength ; and epsilon is the aspect angle at which the land element in question is represented ; and in which, in a vertical pictorial displaying of each azimuth section illuminated by a plurality of radar wave trains, the echo signals of which are each received in consecutive time windows (range gates) and are thus analysed in respect of their Doppler frequency from consecutive range zones (range gate zones) (Ri , Rj ) ; and for displaying on the screen (BS) the light point is vertically-deflected in proportion to the respective aspect angle so that in response to an echo received at a specified aspect angle and with a specified amplitude, the image point which reproduces this echo with a corresponding brightness has a deflection proportional to the aspect angle ; characterised in that the linear array antenna (A) consists of two receiving antenna rods (1, 2) arranged in parallel to one another and which form a DF(direction finding) - antenna and which are spaced by a few wavelengths, for example five ; that each phase difference (G) between echo signals received by the two receiving antenna rods (1, 2) from each one land element (R) are determined by means of phase angle substraction, carried out individually in respect of each range gate, and is stored ; that the Doppler frequency is determined, individually in respect of each range gate ; and that from the phase differences and Doppler frequencies of at least two range gate zones the reference frequency fdmax alpha = see diagramm : EP0076877,P9,F1 is determined, where : - fdi and fdj are the Doppler frequencies established in such range gate zones, Gi and Gj are the phase differences established in the respective range gate zones ; and s is the phase difference gradient dependent upon the respective aspect angle epsilon** ; and that moreover in order that the land may be represented on the radar screen, at least in a middle aspect angle zone (II), i.e. from approximately 15 degrees to 75 degrees, the light point is vertically-deflected at least in approximate proportional to the time curve of the quantity : epsilonII = arc cos see diagramm : EP0076877,P10,F1 where fd is the Doppler frequency which has just been determined.

Inventors

• 👤 Klaus Dr.Ing. Von Pieverling

Bibliographic Details