GB1291275A - Log-periodic antenna array having closely spaced linear elements - Google Patents

Abstract

1291275 Aerials D L CARTER 5 Dec 196 9 [5 Dec 1968] 59491/69 Heading H4A A wideband aerial array comprises at least three monopole or dipole elements of decreasing lengths, the relative lengths of individual elements being determined by a substantially constant scale factor #. The elements are closely spaced, the separation between alternate elements being substantially less than 1/20 wavelength corresponding to the resonant frequency of the smaller of the elements. Means are provided for connecting a transmission line to the smallest element of the array, and there are also provided coupling network means comprising lumped inductive and capacitive reactances feeding said elements such that in a group of elements effective for radiation at a particular frequency alternate elements are substantially in anti-phase. As described a monopole array, Fig. 5, is formed from a flat cable with thin wire conductors encased in a dielectric material. The various stepped elements 51, 53 &c. result from cutting the cable so as to conform with the desired relationship of the lengths of said elements. A coupling network, Fig. 6, comprises inductors and capacitors, a transmission line being connected to the terminals adjacent the smallest element 55. In other embodiments, arrays of dipole elements are provided which may be symmetrically arranged (Figs. 1 and 3, not shown) or be asymmetrically arranged, Figs. 2 and 4. The elements of an array need not necessarily be arranged in planar formation, but may be bunched together in a random grouping.