GB983447A - Improvements in or relating to directional aerials - Google Patents

Abstract

983,447. Aerials. MARCONI CO. Ltd. May 10, 1962 [July 3, 1961], No. 23920/61. Heading H4A. The Specification discloses several types of logarithmic wide band aerial systems each comprising an array of dipoles or folded dipoles resonant at different frequencies throughout the band and which are constructed so that the effective aerial aperture and beam width of the system are constant over the entire band. These characteristics are achieved by incorporating one or more of the following features: (a) making the feeder and dipole elements of relatively highly resistive material (b) varying the impedance of the feeder along its length e.g. by means of a feeder of tapering cross section or of a pair of feeders running at a slight angle to one another (c) mounting an aerial having copper radiating elements and feeders on a panel of " lossy " dielectric material (d) making the cross sectional areas of the individual elements of the array (c) different or when these are folded dipoles by having the ends of the folds of different lengths. Fig. 1 shows an array of twelve dipoles logarithmically spaced and formed as copper deposits on a " lossy " panel P, one half of each element being on one side of the panel, the other half being on the other side as shown by the dotted lines. The elements on one side are joined by a feeder, in the form of a copper deposit and to which is soldered along its length the outer core C2 of the coaxial feeder. The inner core C1 of the coaxial feeder is joined to the remote end of a similar feeder deposited on the reverse side of the panel. A similar arrangement utilizing feeders of tapering cross - section is disclosed (Fig. 3, not shown). The elements in the form of folded dipoles may be deposited on one side only of the panel with the feeders side by side (Fig. 4, not shown). Fig. 6 discloses a similar array made of highly resistive wire and not mounted on a panel, the constant effective aperture over the operating band being achieved by decreasing towards the lower-frequency end of the array the impedance of the loops constituting the dipoles by decreasing the spacing between the X and Y conductors from a maximum for the shortest dipole to a minimum for the longest. A " wire " array in which the feeders taper towards each other is disclosed (Fig. 7, not shown).