Patent GB-1362741-A (GB)
Title: End-fire periodic dipole aerial arrays
IPC: H01Q21/12
Filed: 1973-06-15
Abstract: 1362741 Aerials GENERAL ELECTRIC CO Ltd and T R MORGAN 15 June 1973 [15 June 1972] 28170/72 Heading H4A In an aerial array of parallel dipole elements reactive loading is provided for at least one element by at least one pair of elongated members at each end of a main part of said element. The members of each pair are formed as inverted extensions which diverge in opposite directions from a plane which is parallel to the main parts of the elements and to the axis of the array. As described, a dual-polarized composite array comprises two identical log-periodic dipole arrays A, B, Figs. 1, 2, disposed in respective planes at right angles to each other and intersecting along the axis of the array. There are eleven dipole elements in each array with spacings along the axis, and electrical lengths, in accordance with the log-periodic law. The physical lengths of the main parts of the six lowerfrequency elements, Nos. 6A to 11A and 6B to 11B, are made the same, the requisite electrical lengths of nos. 7A to 11A and 7B to 11B being obtained by reactively loading their ends with one or more pairs of conductive members 12. Said pairs of members are disposed in planes at right angles to the plane of the array and they diverge at angles of 45 degrees from the plane of the array. For the elements 7A, 8A and 7B, 8B a single pair of members 12 is provided at each end, whilst for the elements 9A to 11A and 9B to 11B, two pairs of members are provided at each end. Additionally, conductive straps 14 are associated with the members at the ends of the elements 11A, 11B. Insulating strainers 15 extend each pair of aligned members 12 on adjacent ends of co-planar elements of the two arrays, and rigid insulating spars 16 extend between adjacent ends of the elements 6A to 11A and 6B to 11B. Insulating strainers 17 extend between adjacent ends of the elements 1A to 6A and 1B to 6B. The central feed points of the dipole elements of each array may either be directly connected to a respective two-conductor transmission line which lies in a plane perpendicular to said elements (Fig. 4, not shown) or be directly connected to a respective two-conductor helically wound transmission line, or be connected to a respective transmission line having twin conductors 42, 43 or 44, 45, Figs. 6, 7, by means of square printed circuit boards 41. A hollow rigid square cross-section tube 40 of insulating material provides means for supporting the inner ends of the halves of the dipole elements on its walls, and contains the circuit boards 41. Said boards are inserted alternately in back-to-front relationship in order to obtain the desired phase reversal between alternate elements. Thus, in Fig. 7 the R.H. half of the horizontally disposed dipole element is connected to the conductor 44, and the L.H. half thereof to the conductor 45. In the next dipole the R.H. half is connected to the conductor 45 and the L.H. half to the conductor 44. In another embodiment, each loaded element of a dual-polarized composite array comprising two identical log-periodic dipole arrays, is provided with two pairs of conductive members at each end. A member at the end of a main part of a dipole element of one array, said element main part lying in a particular plane perpendicular to the axis of the array, is directed towards a main part of a dipole element of the other array, said second element main part lying in an adjacent plane spaced from the first plane. The two members are connected by an insulating strainer (Fig. 3, not shown).