Patent GB-1045525-A (GB)
Title: Phase and amplitude control of antenna array
IPC: H01Q3/42
Filed: 1964-04-10
Abstract: 1,045,525. Aerials; radio direction-finding. STANDARD TELEPHONES & CABLES Ltd. April 10, 1964 [April 15, 1963], No. 14878/64. Headings H4A and H4D. A control system for an aerial array comprises a simulation of the array which is illuminated by a source of electromagnetic energy so that the elements of the simulation array produce outputs which are used to control the phases and the amplitudes of the signals transmitted or received by the aerial array. As described, a simulation 71, Figs. 20, 21, of an array of ten mast-type aerials evenly spaced around a circle of diameter equal to one wavelength comprises ten probes 72 projecting from a copper earth plate 73. The probes are illuminated by means of a parabolic reflector 74 having an electromagnetic horn 75 at its focus. The plate 73 is rotatable by a knob 21a. The probes 72 are disposed in coaxial pistons 76 which are slidable in and make electrical contact with cylindrical wells 77 and said probes carry cam followers 79 at their ends which co-operate with a fixed cam track 20, so that their projections from the plate 73 alter as said plate is rotated. Coaxial cables 110 are connected to the probes 72, the outputs of which vary systematically in phase and amplitude as the plate 73 is turned, in simulation of the outputs of the elements of the aerial array with respect to waveforms having corresponding bearings. The knob 21a for turning the plate 73 may be replaced by a motor if a constantly rotating beam is required. The outputs from a simulation array may be con verted in frequency in two stages before application to the aerial array. Thus, in Fig. 10 (not shown), the outputs of frequency f 1  from four simulation elements 49, 50, 51, 52 are connected together with outputs of frequency f 2  from an oscillator 53 to electronic units 54, 55, 56, 57 from which, after mixing, phase compensation, and amplification the resultant signals are fed to mixers 58, 59, 60, 61 together with oscillator outputs of frequency f 3 . The resulting signals of frequency f 0  are amplified in units 62, 63, 64, 65 and radiated from aerials 66, 67, 68, 69. If the frequency f 0  is 1 Mc/s., f 1  may be 300 Mc/s., f 2  may be 290 Mc/s. and f 3  may be 9 Mc/s. Keying or other modulation may be impressed upon the frequency f 2  or f 3 . In a second embodiment, Figs. 16, 17 (not shown), a simulation array comprises pick-up coils 24 arranged as are the aerials in the array and subjected to induction by a linearly travelling magnetic field produced by a plate 7. The coils 24 are supported on rods 15 which are carried by a rotatable plate 13 and which bear with their lower ends on a fixed cam track 20. The rods with the pick-up coils move axially against return springs 14 as the plate 13 is rotated and their ends ride over the cam track, so varying the gaps between the coils and the field plate 7 and, consequently, the amplitudes of the induced voltages. The field plate 7, Fig. 13 (not shown), is made from a dielectric material which may be a ferrite and has grooves 8 in which are wound distributed polyphase windings, Figs. 14, 15 (not shown). The windings may be energized by a polyphase, for example, three-phase valve generator, Fig. 9 (not shown). A single phase source 35 feeds a resistance-capacitance bridge 37 through a transformer 36 with a centretapped secondary and derived voltages at 120 degrees phase intervals are amplified by valves 38, 39, 40 whose ouputs are connected to the windings of the field plate. In a third embodiment, Figs. 18, 19 (not shown), a linear end-fire aerial array is simulated by means of two sets of four coils 33 disposed above a field plate 7 with the sets of coils at right-angles to its slots. The coils are mounted on rods 28 which may be moved up or down in bushings 29 and locked by screws 31. The bushings 29 may be moved longitudinally in slots 32 in a mounting plate 27 and locked by nuts 30. The phases and amplitudes of the voltages induced in the coils 33 may consequently be adjusted. For a broadside array, the two sets of four coils would be arranged to be parallel to the slots of the field plate 7 and for a steerable array the mounting plate 27 would be arranged for rotation above the field plate 7. In a fourth embodiment, for reception, the aerial array 80, Fig. 22 (not shown), may comprise directional elements for example, loop aerials, which are steered by a servo system in correspondence with the movements of a steerable simulation array 88. When receiving from a station of known bearing the orientation of the simulation array may be pre-set; otherwise it may be rotated until maximum strength signals are received from a station, where its orientation will indicate the bearing of the said station, in the manner of a direction-finder. Signals of frequency f 0  received by the aerials are mixed with the outputs of frequency f 3  from a local oscillator 85 to produce resultant outputs of frequency f 03  (=f 0 -f 3 ). Similarly, signals of frequency f 1  from the elements of the simulation array are mixed with the outputs of frequency f 2  from a local oscillator 97 to produce resultant outputs of frequency f12 (=f 1 -f 2 ). The signals of frequencies f 03  and f 12  are fed to second mixers and the final signals of frequency f 03 -f 12  are combined in phase at the input of a receiver 104. The mixers may include phase compensation means and the local oscillator 85 may have a keyer 86 in tandem to disable reception during transmission if a radar or other pulse system is involved.