A plane wave spectrum scattering analysis of the effects of a near-zone obstacle on the pattern performance of a directive antenna is discussed. The free-space azimuth monopulse antenna is characterized by its sum and difference mode plane wave spectra, and a computed plane wave scattering dyad is used to characterize the scattering by a metallic right circular cylinder when it is excited by the incident antenna spectra. An efficient computer algorithm has been developed to compute the far-zone scattered and total fields for the antenna/cylinder system. Extensive experimental data have been obtained, and the patterns calculated using the present analysis are in agreement with the measured data.

Plane wave spectrum scattering analysis of near-field obstacle effects on directive antenna patterns

An analytical model is presented which describes the farfield radiation pattern of an array antenna blocked by a vertical or horizontal metallic cylinder in the near field of the aperture. The implementation of this model as a generalized computer program has been completed, and the computed radiation patterns have been verified by extensive measurements on a low sidelobe X -band slotted waveguide array. The effects of the blockage are summarized graphically for a wide range of obstacle sizes and distances, and for aperture illuminations ranging from conventional reflector-type distributions to ultralow sidelobe distributions. Using dielectric or absorptive coatings to improve the radiation pattern in the presence of cylindrical obstacles is proposed as a logical extension to the existing model.

Near-field blockage of an ultralow sidelobe antenna

An analytically simple and numerically efficient technique for calculating the pattern distortion of aperture antennas radiating in the presence of conducting platforms located in the near or far field of the antenna is presented. The technique presented, based on uniform geometrical theory of diffraction (UGTD), is also applicable for large aperture antennas (aperture area > 15 \lambda^{2} ). An excellent agreement between the calculated and measured results obtained for a typical aperture antenna mounted on a conducting platform confirms the validity of the analytical technique developed.

Pattern distortion of aperture antennas radiating in the presence of conducting platforms

A genetic algorithm optimization scheme for planning satellite earth station antenna layouts is presented and analyzed A method for quantifying the value of an antenna layout is described This scheme allows for the optimal placement of large antennae within a bounded geographic area, making the best use of earth station land Performance of the optimization scheme is illustrated by simulation results

Optimization Of A Satellite Earth Station Layout Using Genetic Algorithms

Comments on "On some broad-band microstrip resonators"

A technique for the calculation of the radiation patterns of radar antennas with single near-field cylindrical obstructions is described. The computed and measured results are compared for a highly directional S band-radar antenna. Consideration is then given to the possible extensions of the method for cylinders of finite length and of noncircular cross-section, as well as for 3-dimensional radars.

http://ieeexplore.ieee.org/iel5/5247218/5250617/05250646.pdf

A.J. Hissink

Papers

Radar antenna with near-field cylindrical obstruction. Computer-program description