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1.5
FUNCTIONAL DESCRIPTION
The antenna radiates a beam 1.5 degrees in azimuth and shaped in elevation to produce coverage up
to approximately 32 degrees above the horizon to provide a map-type presentation of aircraft within
55 nautical miles of the airport terminal. Major assemblies of the antenna are described in the
following paragraphs. This section gives only a brief description of the function performed by each
without regard to functional operation. A detailed analysis of functional operation is contained in
Section 1.6, Theory of Operation.
1.5.1
Antenna Unit
The antenna unit consists of Reflector, Dual Feed Assembly, interconnecting waveguide, cables and
wires. The antenna produces a rotating antenna pattern having a 1.5 degree azimuth beamwidth and a
shaped elevation pattern allowing radar coverage up to 32 degrees above the horizon. Polarization of
the radiated energy can be remotely switched to either linear or circular polarization. Special
equipment includes a test antenna and a telescope used to check antenna alignment.
1.5.1.1
Reflector
The reflector has a modified parabolic shape designed to produce an approximately cosecant-squared
beam in the elevation plane. The reflecting surface, covered with expanded aluminum screen, is 16.1
feet wide and 9 feet high. The horizontal and vertical contour plates are fabricated using numerically
controlled equipment to ensure the required high degree of accuracy. Wind loads are transferred to
the reflector support through the base of the reflector and the back structure which consists of welded
aluminum tubes and channels.
1.5.1.2
Dual Feed Assembly
The dual feed assembly includes two identical polarizer/feed assemblies. Each polarizer/feed
assembly contains a square waveguide section with the necessary motor and gearing to generate
either linear or circular polarization as selected by the radar operator. The antenna feedhorn, which
mounts on the polarizer, provides impedance matching between the waveguide system and free
space, and produces the desired feed pattern to illuminate the reflector. A radome over the horn
aperture excludes moisture and foreign matter, and provides a pressure seal.
1.5.2
Polarization and Beamswitch Control Box
The Control Box mounted on the feed support provides for interconnection between the antenna unit
and the Rotary Joint connections.
10
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