GB1143579A - - Google Patents

Abstract

1,143,579. Aerials. DORNE & MARGOLIN Inc. 13 July, 1966 [14 July, 1965], No. 31559/66. Heading H4A. In an aerial 10 a transmission line 14 from a transmitter (or receiver) 12 is electrically coupled to some at least of a plurality of spaced radiating elements 11-1 to 11-n. All elements have portions extending generally in a first direction relative to the transmission line (as shown, at right angles thereto) and some have further portions 11-1a to 11-5a, extending in a second direction (as shown, parallel to the transmission line), said further portions being electrically coupled together. As described, the line 14 centre feeds the dipoles 11-1 to 11-n of a log-periodic aerial 10. The dipole 11-1 at the rear end is also provided with additional portions 11-1b, at the ends of the portions 11-1a, which are bent inwards in the first direction, i.e. at right angles to the line 14. The electrical coupling between the portions 11-1a, 11-2a &c. is capacitive and it may be increased by connecting variable capacitors (19), Fig. 1A (not shown). The overall length of any dipole is substantially one half-wavelength at its mean operating frequency, and folding decreases its transverse dimension. It may thus be arranged for the width of the aerial to be one quarter of the wavelength at the lowest operating frequency. In a second embodiment (Fig. 2, not shown) a log-periodic aerial (50) comprises monopoles (51-1) to (51-n) connected to a single wire feeder (46) run above a ground plane (44). Phasing circuits (53) are connected from points on the feeder between each pair of monopoles, to ground, to ensure the requisite 180 degrees phase relationships. In a third embodiment (Fig. 3, not shown) two log-periodic aerials (60), (70) of the kind described, and covering different wavebands, are connected by a common transmission line (74) to a transmitter (or receiver) (12). In a fourth embodiment (Fig. 4, not shown), dipoles (81-1) to (81-4) having folded portions (81-1a) to (81-4a) and located at the rear end of a log-periodic aerial (80) are not connected to the transmission line (14) and are fed only by capacitive couplings between the said folded portions.