GB1289741A - - Google Patents

Abstract

1289741 Monopulse radar LICENTIA PATENT VERWALTUNGS GmbH 24 Dec 1969 [9 Jan 1969] 62915/69 Heading H4D In a phase monopulse radar, angular deviation, in two planes, e.g. azimuth and elevation, of targets from the aerial boresight is measured using five aerials, three for each plane, and for each plane combining the signals received at each aerial V 1 , V 2 , V 3 to produce the quantities (V 1 eiu1 - V 2 ), (V 2 eiu<SP>1</SP> - V 3 ) and (V 1 eiu 1 - V 2 )eiu<SP>2</SP>, where u 1 and u 2 are proportional to the azimuth or elevation angular displacements of two targets, the above quantities being used to determine u 1 and u 2 . In a first embodiment, five aerials are used in a cruciform in a plane Lr to the aerial boresight, Fig. 3. The signals received by the three aerials in the azimuth plane are given by where An = signal amplitude from target n U n = K.l.sinα n K =2#/# i α n = azimuth angle of target n l = displacement of adjacent aerials. These signals are fed to apparatus, Fig. 5, wherein V 1 undergoes a phase shift, V 2 is subtrated therefrom and the amplitude of the resultant is detected and compared with a signal derived from V 2 and V 3 in a similar manner. The above equations show that if this difference in amplitude is zero, the phase shift of V 1 and V 2 is u 1 = K.l.sinα 1 . Thus the difference signal is utilized in a feedback loop to control the two phase shift elements and the final value of phase shift determines α 1 . The equations also show that Thus the signals produced above are subtracted after the former has undergone a phase shift and the difference is fed-back to control the phase shift element. At balance the value of phase shift is u 2 =Klsinα 2 . The same procedure us used to derive the two elevation angles # 1 , # 2 . This method however gives two possible sets of co-ordinates, shown in Fig. 6 as circles and crosses respectively. In order to correlate the co-ordinates to each other, the aerial is swivelled until the boresight bisects the two azimuth angles and the two elevation angles. It is then rotated anti-clockwise about the boresight. If the elevation angles become zero first, the circles denote the targets: if the azimuth angles become zero first, the crosses denote the targets. If only one target is present, the first phase shift control voltage is zero for whatever phase shift is applied and the co-ordinates of the single target are obtained from the second phase shift elements in each plane. The same general principles are described as being applied to a system for resolving three targets (Fig. 8, not shown). In this case seven aerials are used, one extra for each plane. The correlation procedure also applies the same procedure but is much more complex. In general, to resolve v targets v + 1 aerials are used in each plane with one aerial common to both planes.