Abstract.
The
approaches to increase the noise protection level of parabolic
antennas through inclusion of angular filters of antenna radiation into
the radiotransparent radomes have been investigated
in this paper. Various configurations of radomes with the antenna
hood, having the absorbing material, and angular filters, which together allow
reducing the rear and far lateral radiation of the antenna, are considered. The
comparison of radomes' radio-technical characteristics, obtained experimentally
and in numerical simulation, are presented. The advantages and shortcomings of
the known angular filter construction, based on four grids of wires, have been
examined. This filter is characterized by strong angular filtration capability,
but its manufacturing requires very accurate tolerance holding. The angular filter
with elements, having substantial electric moments, and its equivalent circuit
analog for electrodynamic analysis of the filter's properties are presented. Vibrators
and spirals of length much less than wavelength were used as elements with substantial
electric moments. In case of spiral elements their diameter must be much less
than length. Angular dependences of transmission coefficient of filter with
spiral elements, calculated with software package FEKO and measured, are
compared. The measured direction patterns of the parabolic antenna, which is
used in radio-relay communication and has the hood with the absorbing material
attached, two angular filters, made of resonant vibrators, and the three-layered
protecting dielectric wall, are presented. Inclusion of angular filters into
the hood is shown to considerably reduce the level of rear and lateral radiation
of parabolic antenna. Furthermore, angular filter production technique is quite
simple and doesn't require holding strict tolerance.
Key words:
parabolic
antenna, antenna hood, angular filter, rear and lateral radiation, radome.
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