GB1026112A - Antenna system - Google Patents

Abstract

1,026,112. Aerials. BLASS ANTENNA ELECTRONICS CORPORATION. Nov. 11, 1963 [Dec. 12, 1962], No. 44341/63. Heading H4A. [Also in Division H1] A steerable pencil beam is produced by a horn feed 40 and a reflector 30 comprising a planar array of secondary elements each at one end of a respective straight transmission line containing a longitudinally adjustable reflecting means so that the signal re-radiated by each secondary element is delayed relative to the radiation signal incident thereon, the different reflecting means being relatively adjusted so that the secondary elements focus the radiation transmitted or received by the primary feed in the same manner as a paraboloidal reflector, the orientation of the effective paraboloid (and hence the direction of the beam) being varied by varying the longitudinal positions of the various reflecting means. As described, each secondary element comprises either (1) the open end 32 of a ridge waveguide 34, Figs. 1 and 2, which constitutes the delay line, the apertures 32 being covered by a fibreglass radome 35, Fig. 2; or (2) a dipole 32<SP>1</SP> coupled to a coaxial line 34<SP>1</SP>, Fig. 10, a plane reflector 32<SP>11</SP> being spaced #/4 behind the dipoles 32<SP>1</SP>; alternatively, each secondary element may be a small horn. Each adjustable reflecting means may comprise a sliding metal shorting plunger but as described with reference to Figs. 3, 4, 4A and 5 (not shown), it comprises four shunt diodes uniformly spaced at #/8 intervals along the guide which are selectively rendered conductive by a beam director unit 80 to short-circuit the guide, the resultant effect being that the beam direction is changed in small discrete steps. The beam director unit presents appropriate signals to X and Y scan control generators (Fig. 7, not shown), whose outputs are presented to scan control networks consisting of conventional digital circuitry to provide phase delayed signals along the X and Y axes of the array through a flip-flop controlling the condition of the diodes in the guides 34 (Fig. 8, not shown). An additional digitally controlled signal (Fig. 9, not shown), may be provided between the binary circuit and the flip-flop to provide spherical correction. A plurality of separate feeds 40 may be used in conjunction with a single reflector 30 and in order to provide hemispherical scanning three separate systems 30-1, 30-2 and 30-3 may be arranged as shown in Fig. 11 and Fig. 12 (not shown).