GB815061A - Improvements relating to wireless aerials - Google Patents

Abstract

815,061. Aerials. SHARDLOW ELECTRIC WIRES Ltd., and JONES, P. Feb. 24, 1956 [Nov. 26, 1954], No. 34420/54.. Class 40 (7). Resonant couplings are used in an aerial system effective at two different frequencies (or over two different frequency bands) to cause a dipole or folded dipole to be effective at a lower frequency and to couple a part of it to form an aerial for a higher frequency. In a first embodiment a folded dipole D, D1 associated with a suitable feeder is resonant for operation at one frequency and electrically resonant couplings bridging the elements are provided which have negligible effect at that frequency but which act as acceptor circuits at another frequency to bridge the elements and form a folded dipole at the higher frequency. The resonant coupling consists of an inductor I in series with one or two capacitors (C, C1). The, or each, capacitor may be formed as a single conductive plate, the folded dipole rod or tube forming the other condenser element and a dielectric separator being provided. The whole coupling may be formed in a moulded housing with either single capacitor plates for capacitive coupling to the dipole or with conductive connections and internal capacitors. The resonant circuit inside the housing may be formed by either wired or printed circuit techniques. It is stated that two or more pairs of couplings could be used to render the aerial system effective at three or more frequencies. The arrangement shown in Fig. 1 may be associated with a reflector for the lower frequency and directors for the higher frequency or may be a unit in an array of like elements. In another embodiment a coupling of the kind described is used in conjunction with each section of the aerial described in Specification 734,689 to cause this aerial to be effective at two different frequencies. In a further embodiment a simple dipole A is made resonant at one frequency and a parallel element is coupled to corresponding points on it by resonant couplings I, C, to form a folded dipole effective at a higher frequency.