GB590413A - Antennae for broad frequency band operation - Google Patents

Abstract

590,413. Aerials. STANDARD TELLPHONES & CABLES, Ltd., and WILLOUGHBY, E. O. Jan. 1, 1945, No. 98. [Class 40 (v)] A broad band directive radio antenna comprises a single linear slot formed by the oppositely disposed edges of conducting sheets and substantially aligned with the desired directivity; feeder means are coupled to opposite points on the edges of the slot at or near one end of it and the width of the slot for at least half its length is made a sufficiently small fraction of the operating wavelength to ensure end fire directivity. The conducting sheets may be flat or curved. The ends of the slot may be short-circuited, left open, flared out, or terminated by the characteristic impedance 8, Fig. 1, of the transmission line formed by the conductors each side of the gap ; the latter arrangement is claimed to give the best directivity, but with a power loss of about 3 decibels. The conducting sheets whose edges form the antenna may be spaced over a parallel conducting sheet and, if desired, the outside edges of the antenna sheets may be bent down and attached to the parallel sheet, forming a slotted open-ended tube. In another form of the antenna, the slot may be formed between the edge of one conducting sheet and the surface of another, the sheets being preferably perpendicular to each other. In a further form, a groove or indentation is formed in a conducting sheet, the depth of the groove being an odd number of quarter wavelengths and the gap at the top of the indentation being the antenna slot. The slot antennas may be used for transmission or reception and the feeders 12 are connected at one end (Fig. 1) unless the end is short-circuited when they should be attached approximately a quarter wavelength from it (Fig. 8). A discussion of the theory of the antennas is given. Specification 515,684 is referred to.