GB1282293A - Improvement to wide band antennas - Google Patents

Abstract

1282293 Aerials LIGNES TELEGRAPHIQUES ET TELEPHONIQUES 17 Oct 1969 [23 Oct 1968] 51167/69 Heading H4A A wide band aerial comprises a conductive wire 1, Fig. 1, and a sleeve 3 of ferromagnetic material which surrounds said wire over a part (e.g. 10%) of its length. A serially connected adjustable lumped impedance may also be provided. It is arranged that the following relationship holds within the operating frequency band: where, The sleeve 3, Fig. 1, is located at the end of the wire 1 which is connected to a transmitter or receiver 2, and it is made of a material such as a ferrite, the permeability of which varies with frequency so as to allow the above relationship to be satisfied. The upper part of the sleeve 3 is tapered to improve matching, and a dielectric ring 4 is also provided for the same purpose. The sleeve 3 and the ring 4 are protected by potting material 5. In another embodiment, a construction similar to that shown in Fig. 1 is provided at the free end of the conductive wire (Fig. 7, not shown), but the ferromagnetic material has a permittivity which varies with frequency so as to allow the above relationship to be satisfied. A third embodiment (Fig. 5, not shown) having a ferromagnetic sleeve at the base end of the conductive wire, features automatically controlled D.C. biasing of said sleeve. A fourth embodiment (Fig. 6, not shown), also with a ferromagnetic sleeve at the base end of the conductive wire, has a series inductor with ferromagnetic core. Automatically controlled D.C. biasing of said inductor core is provided. The use of a varactor diode as a series impedance is mentioned.