Showing papers on "Coaxial antenna published in 1968"

Multiple polarization spiral antenna

Abstract: APPARATUS AND A METHOD OF EXCITING A MULTI-ELEMENT LOG SPIRAL ANTENNA TO OBTAIN LEFT-HAND AND RIGHT-HAND CIRCULAR POLARIZATION RADIATION. THE ANTENNA ELEMENTS ARE INTERWOUND IN THE USUAL MANNER IN TE FORM OF EITHER EQUIANGULAR OR ARCHIMEDES SPIRALS TERMINATED AT A CIRCUMFERENCE CONSISTENT WITH A DESIRED RADIATION PATTERN. EACH ELEMENT OF THE ANTENNA RECEIVES MULTIPLE CURRENT MODE EXCITATION AT THE INNER TERMINALS. TYPICALLY, AN ANTENNA EXCITED BY FIRST, SECOND, FOURTH, AND FIFTH MODE CURRENTS PRODUCES BOTH LEFT-HAND AND RIGHT-HAND, FIRST AND SECOND MODE, CIRCULAR POLARIZED RADIATION WHEN TERMINATED AT AN APPROPRIATE CIRCUMFERENCE.

Radiation fields of the short-backfire antenna

Abstract: A method for the approximate calculation of the radiation fields of a short-backfire antenna is presented. This technique is based upon the assumption that the aperture field is distributed approximately cosinusoidally in both horizontal and vertical planes as evidenced by near-zone field measurements. It appears that the short-backfire antenna is essentially a circular aperture antenna with cosinusoidal aperture field, and that the dipole functions merely as an exciter for this field.

Picture framed antenna

Abstract: A television antenna adapted for indoor use which is maintained obscured by serving as the backing member for a picture frame and picture which antenna includes a thin rigid dielectric circuit board having a circuit pattern thereon approximating a dipole antenna. The television antenna wire serves to position a backing easel to properly incline the antenna for maximum reception. Antenna extensions from the main antenna are provided to adjust the electrical length of the antenna in poor reception conditions. In another embodiment, a folded dipole antenna is provided by means of three circuit boards disposed in three hinged picture frames forming a horizontal array in which the antenna pattern on the circuit boards is made electrically continuous through connections in the hinges of the picture frames.

A reciprocity relation between the transmitting and the receiving properties of an antenna

Abstract: A reciprocity relation between the transmitting and the receiving properties of an antenna is derived. In the transmitting situation a certain part of the antenna, called “source domain”, is capable of carrying external currents, both of the electric and the magnetic type. In the receiving situation a plane electromagnetic wave is incident upon the antenna system. Whereas the customary way of deriving reciprocity relations in antenna theory starts with considering two separate antennas, the present method assumes a single antenna only.

Planar radial array with controllable quasi-optical lens

Abstract: Antenna feed apparatus for use in electronically scanned phasedarray antenna systems. In a transmit mode of operation, input power to be fed to an array of m antenna elements is applied to a multimode hybrid launcher wherein a sum signal is generated and applied to the input of a high-power level multitier radial line power divider. The sum signal is divided by the radial line power divider into n equivalued output signals of reduced power level. The n signals are then divided into m signals of varying power levels by a low-power level stripline power divider, and applied via m transitions to m phase shifters associated with the array of antenna elements. Each phase shifter operates under the control of a beam-steering control unit to insert a differential phase shift in each antenna element channel whereby a desired phase front is established across the aperture of the antenna array. In a receive mode of operation, monopulse signals received by the antenna array from a target are combined by the power dividers and applied to appropriate sum, elevation difference, and azimuth difference ports of the hybrid launcher.

Omnidirectional antenna having circumferentially spaced radiators with orthogonal polarization

Abstract: In an omnidirectional antenna of the type including plural individual radiators arranged around the circumferential periphery of a preferably cylindrical body whose diameter is large relative to the operating wave length of the antenna, the respective polarization directions of peripherally adjacent individual radiators are perpendicular to each other. The radiation patterns of the individual radiators overlap in the range of their respective half powers (3db-points). The antenna has a circular radiation characteristic formed by simple addition of the radiation patterns of the individual radiators.

Conical logarithmic-spiral antenna

Abstract: The invention is for an antenna of the conical logarithmicspiral class. Specifically there is disclosed a means of utilizing a terminating active region to reduce the overall size of such an antenna by a factor of two without significantly modifying the antenna characteristics. Reference is made to the claims for a legal definition of the invention.

Novel helical antenna

Abstract: A directional electromagnetic radiating antenna with circular polarization capable of operating over wide frequency bands and having a greater electrical length than actual physical length. The invention applies basically to a helical antenna utilizing one or more unifilar or multifilar windings which possess the characterizing feature of having an increased electrical path length whereby the operating characteristics of the antenna will resemble that of a larger physical structure than is actually necessary to support the hardware comprising the antenna.

Concealed windshield broadband antenna

Abstract: An AM-FM antenna for vehicular radio receivers comprising a pair of L-shaped fine wire conductors disposed between the laminates of a windshield in reversely symmetrical relation and connected to a receiver by way of a coaxial lead. Spacings between the conductors and the vehicle body portion bounding the windshield are chosen to capacitively load the antenna for AM reception and to resonate the antenna for FM reception.

A loaded antenna system applied to VHF portable communication equipment

Abstract: The technique of impedance loading to the antenna element has been applied to an antenna system for portable VHF communication equipment and its practical usefulness has been shown with a brief theoretical analysis and some experimental results. By means of impedance loading to the antenna element, the driving point impedance may be varied so as to make matching feasible, even though the element length is very short, and the effective length may be increased, so that the gain of the loaded antenna system relative to a non-loaded antenna system may be increased. As a practical example, an inductance loaded antenna system has been applied to a 34-54 MHz range portable communication equipment and about 5 dB relative gain increase has been observed.

Measurement of antenna current distributions in a hot plasma

Abstract: The current distributions on a cylindrical monopole antenna in hot plasmas of varioas densities have been measured. It has been observed that the antenna carrent distribution is essentially controlled by the electro-magnetic mode when the antenna frequency is higher than the plasma frequency. When the antenna frequency is lower than the plasma frequency, the antenna current distribution exhibit unusual behavior. The effect of the electroacoustic mode on the antenna current is discussed.

Short high-frequency antenna and feed system therefor

Abstract: An antenna system is described wherein a short antenna of about 0.1 lambda or less is employed with a coaxial cable feed. The coaxial cable is directly connected to ground at but one end thereof and is coupled to ground at the other end via a capacitor. The capacitor is selected to provide good matching of a transceiver to the antenna with or without a coupler. In an alternate antenna system a loading network is employed which is mounted within the antenna to provide a stably performing antenna throughout adverse weather conditions such as rain, snow or ice.

Broadband cornucopia-type antenna system

Abstract: The present invention describes a broadband, low-profile circularly polarized antenna, primarily for airborne applications which has a substantially omnidirectional radiation characteristic in the horizontal plane. The form factor of the antenna comprises a cornucopia-shaped element having an arcuate surface which is defined by a plurality of polynomial line segments and which diverges from one terminal end to the other.

The determination of far field antenna patterns using Fresnel probe measurements

Abstract: Apparatus and method for the design and measurement of microwave antenna wave patterns. The far-field radiation pattern of a space fed aperture antenna is determined as a function of the measured radiation characteristics at the antenna focus and the design or measured illumination characteristics of the feed radiator of the antenna.