Showing papers on "Fresnel zone antenna published in 1979"
TL;DR: A method of significantly improving the resolution of systems used for interrogating the spatial variation of permittivity of biosystems at S band is described by immersing the transmitting antenna, receiving antenna, and the target into a material with a high dielectric constant, namely water.
Abstract: This paper describes a method of significantly improving the resolution of systems used for interrogating the spatial variation of permittivity of biosystems at S band. The basic principle employed is to contract the wavelength of the interrogating radiation and to reduce the physical aperture of the interrogating probes by immersing the transmitting antenna, receiving antenna, and the target into a material with a high dielectric constant, namely water. The antenna design is described, and line scans employing transmitted and reflected energy are presented.
69 citations
TL;DR: In this paper, the peak cross polarization in reflector antennas is derived in terms of the polarization efficiency and an approximate expression for peak cross polarization is derived for symmetrical and offset reflectors.
Abstract: Cross polarization in reflector antennas is related to the polarization efficiency. Simple approximate expressions for the peak cross polarization are derived in terms of the polarization efficiency. Front-fed, Cassegrainian, and offset antennas are considered. It is shown that symmetrical antennas have lower peak sidelobes than offset antennas with the same polarization efficiency by approximately 2.5 dB. Excellent agreement between the present method and other methods is achieved. Formulas for the off-axis angle at which peak cross polarization takes place are also given for symmetrical and offset reflectors. It is found that for reflectors with the same D/\lambda ratio, symmetrical antennas have larger off-axis angles (1.6 times larger) for peak cross polarization in comparison with offset antennas.
11 citations
TL;DR: In this article, a study of the radiation characteristics of dielectric tube antennas is made with a possibility of its application in communications satellites, and it has been shown through a systematic analysis that a multimoded dielectrous tube shows a dip in the boresight region which is suitable for satellite antennas.
Abstract: A study of the radiation characteristics of dielectric tube antennas is made with a possibility of its application in communications satellites. It has been shown through a systematic analysis that a multimoded dielectric tube shows a dip in the boresight region which is suitable for satellite antennas.
10 citations
01 Jan 1979
TL;DR: In this article, a systematic study of traveling wave dielectric-rod antennas of different types is described and development of design for several leaky-wave antennas is presented together with experimental results.
Abstract: A systematic study of traveling wave dielectric-rod antennas of different types is described. Development of design for several leaky-wave antennas is presented together with experimental results. Existence of surface-wave radiation in end-fire direction is exhibited and methods to suppress it are discussed.
9 citations
TL;DR: In this paper, the principal H-plane of corner reflector antennas has been determined from computed and measured phase patterns using numerical methods, and the relation between the computed phase centre and various antenna parameters is investigated and presented as graphs.
Abstract: Phase centres in the principal H-plane of corner reflector antennas have been determined from computed and measured phase patterns using numerical methods. They are in reasonably good agreement with each other. The relation between the computed phase centre and various antenna parameters is investigated and presented as graphs.
5 citations
TL;DR: In this article, the role of aperture shape in influencing the far-zone radiation pattern in the vicinity of the main beam of horn-reflector antennas is examined, and the three major types of horn reflector antennas are considered-pyramidal, diagonal, and conical-and the influence of their aperture shape on the spatial character of antenna radiation is assessed.
Abstract: The role of aperture shape in influencing the far-zone radiation pattern in the vicinity of the main beam of horn-reflector antennas is examined. The three major types of horn-reflector antennas are considered-pyramidal, diagonal, and conical-and the influence of their aperture shape on the spatial character of antenna radiation is assessed.
3 citations
08 May 1979
3 citations
18 Jun 1979
3 citations
TL;DR: In this paper, the authors obtained some estimates for the effective sidelobe levels generated by scatterers in the main beam of the antenna by 1) ships and other discrete SCAs in the far field; 2) the sea in the near field; and 3) the ship's own superstructure in the Fresnel region.
Abstract: The far-field radiation patterns of radar antennas when installed aboard ships may differ substantially from their free-space or theoretical design radiation patterns. We obtain some estimates for the effective sidelobe levels generated by scatterers in the main beam of the antenna by 1) ships and other discrete scatterers in the far field; 2) the sea in the far field; and 3) the ship's own superstructure in the Fresnel region.
3 citations
TL;DR: In this article, a local evanescent-wave tracking method was proposed for the analysis of large reflector and aperture antennas, which is based on local evane-centre tracking.
Abstract: A new method based on local evanescent-wave tracking is proposed for the analysis of large reflector and aperture antennas.
2 citations
18 Jun 1979
18 Jun 1979
18 Jun 1979
TL;DR: In this paper, the results of an investigation of flux redistribution at the focal region of a planar Fresnel ring mirror were reported, where a parabolic mirror of large aperture was used to provide a parallel beam of light which was directed at the Fresnel test object.