GB653018A - Improvements in or relating to aerial systems - Google Patents

Abstract

653,018. Aerials. MINISTER OF SUPPLY. May 10, 1948, No. 12840. [Class 40 (vii)] An aerial system with a polar diagram similar to that of a #/2 dipole in which the radiation emitted in the median plane is circularly polarized comprises a coaxial feeder with a flange 3 extending from the end of the outer conductor 2, the inner conductor 1 extending #/4 beyond the flange and a pair of diametrically opposite axial slots 4 and 5 of length #/4 being formed in the outer conductor, the slots 4 and 5 being continuations of radial slots 6 and 7 also of length #/4 formed in the flange. The slots 4, 5, 6 and. 7 are energized by probes 9 which extend radially inwards from the end of the outer conductor and are covered by a cylindrical dielectric block 8 with a radial dimension d given by d(##-1) = #/4, where # is the dielectric constant. The unipole 1 in conjunction with the flange 3 has a polar diagram similar to that of a #/2 dipole with the electric vector parallel to the unipole and the resultant radiation from the slots 4 and 5 has a similar polar diagram with the electric vector perpendicular to the unipole and since the dielectric mass 8 retards the phase of the radiation from the slots by 90 degrees, the resultant radiation from the unipole and the slots will be circularly polarized. Alternatively the outer surface of the dielectric block might be part spherical and the block may be associated with the unipole instead of the slots. The aerial is stated to be of use for installation on craft subject to erratic movements, e.g. balloons.