GB1412569A - Antenna system using variable phase pattern synthesis - Google Patents

Abstract

1412569 Aerials HAZELTINE CORP 21 Feb 1974 [25 May 1973] 7846/74 Heading H4A An aerial system providing a desired radiation pattern comprises an aperture and means for supplying thereto a composite wave energy excitation having amplitude and phase distributions substantially equivalent to the superposition of a plurality of component aperture excitations. Said plurality includes a reference component excitation and other component excitations, having both positive and negative phase variations on said aperture with respect to said reference excitation, any said component excitation with positive phase variation having with respect to said reference excitation an average phase displacement which is a first monotonic function of said phase variation, and any said component excitation with negative phase variation having with respect to said reference excitation an average phase displacement which is a second monotonic function of said phase variation. All excitations have the same sense of average phase displacement. In a first embodiment a collinear array of dipoles 10a to 10h, Fig. 1a, is mounted in front of a ground plane 11. Transmission lines 12a to 12h connect the dipoles to respective directional couplers 13a to 13h. The directional couplers are in series and are connected to a common input port by a transmission line 14. Resistive terminations 15 are provided for the end of the line 14, and for the isolated outputs of the directional couplers. The amplitude of the signal fed to each dipole is dependent upon the value of the coupling co-efficient of its associated directional coupler, and the phase thereof is dependent upon the electrical length back to the input port as determined by the main and branch transmission lines and the directional coupler. It is evident that individual adjustments may be made of the amplitudes and phases of the signals which are simultaneously coupled to the dipoles 10a to 10h. For example, it may be desired to obtain a substantially uniform amplitude of wave energy over an angle of ŒA, without radiation outside that angle. This may be obtained by superposition of the component uniform amplitude excitations 17<1>a to 17<1>e, Fig. 4a. In this figure, the excitations 17<1>a and 17<1>e have the same average phase displacement x<1>, and the excitations 17<1>b and 17<1>d have the same average phase displacement x, from the excitation of reference phase 17<1>c. The amplitudes of the resultant excitations for the various dipoles vary little from an average value (Fig. 4b, not shown) as compared with a prior art arrangement, where those for the dipoles 10d, 10e greatly exceed those for the other dipoles (Fig. 3b, not shown). In another embodiment, a linear array of slots 20a to 20l, Fig. 5a, in a narrow wall of a rectangular waveguide 19 is fed from one end thereof. The amplitude of the excitation of a particular slot is determined by the angle of inclination of the slot, and its phase by the position along the waveguide of the slot. The arrays may be operated in association with reflective or transmissive focusing means. The invention may be extended to planar or cylindrical arrays of elements.