GB1293459A - Corporate-network printed antenna system - Google Patents

Abstract

1293459 Aerials RCA CORPORATION 26 March 1970 [1 July 1969] 14828/70 Heading H4A An aerial array comprises a plurality of dipole elements with the planar first half portions 12 thereof fixed to the top of a sheet of insulating material 15 and the planar second half portions 14 thereof fixed to the bottom of said sheet. A corporate feed network comprising opposed conductive strips 17, 19 on the faces of the sheet 15 connects each dipole element 11 to a common feed point 31, so that the length of feed line from any dipole element to said feed point is the same. The sheet 15 may be <SP>1</SP>/ 32 inch thick and be made of a low-loss polyolefin, having a dielectric constant of 2.32. The dipole half portions are fan-shaped to increase the operating bandwidth, and they and the feed network may be formed by a printed circuit process. Each dipole element is fed by the network through a series of quarterwavelength and half-wavelength transformers (the wavelength being taken at the mean operating frequency of the array) to minimize mismatching at junctions, and to make the input impedance at the common feed point equal to the individual dipole element impedance Za. The balanced impedance presented at the point 37, Fig. 2, by half the array is Za and this is transformed to an unbalanced impedance 2Za at the point B by tapering down the upper conductor 17 only of the feed line. An unbalanced impedance of 2Za is likewise presented by the other half of the array at the point B, and the combined load of impedance Za is connected by line section 57 to a coaxial cable at the point 31. A vernier impedance matching device 58 is formed by a small chip of dielectric material with a copper coating on its upper surface. It is moved to an optimum position along the line section 57, and is then cemented in place. In the network the widths of the conductive strips 17, 19 are proportioned to the characteristic impedance required (e.g. Za or 2Za) and one quarter-wavelength notches are cut at T-junctions where horizontal sections branch into vertical sections, to reduce undesirable current flows. A reflector 23, Fig. 5, may be provided, the sheet 15 being spaced therefrom by a foamed material layer. To provide weather proofing and mechanical protection, a dielectric sheet may be spaced from the other side of the sheet 15 by another foamed material layer.