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instructions on the plates, the size of the plates relative to
the radomes, or the interfaces between the plates and the
radomes. The support plates are fitted with hardware
coding which allows to install the plate to the azimuth
positioner in only the correct way, and which give
information to the test facility about the position of the
radar antenna inside the radome.
The installation platform is 0.8 m above the chamber
inside floor level, so that installation personnel has best
handling control of both the size and the weight of the
radomes. The radar antenna is lowered below the support
plate interface frame before a new radome is installed.
Thus it is virtually impossible to damage the radar
antenna with the radome during installation.
Lifting and lowering of the gimbal positioner is done
automatically by the software. The radar antenna can only
be lowered below the interface frame when the gimbal is
set close to zero azimuth and zero elevation because of a
limit switch interlock mechanism included in the gimbal
positioner / vertical lift, thus preventing that the radar
antenna hits the interface frame. The radar antenna cannot
be lifted to a height which would allow the antenna to hit
the radome wall, because the support plate includes limit
switch information for the vertical lift.
4.2 Personnel Safety
Personnel safety relates to the risk that an operator of the
facility, or any other person, gets hurt by this facility.
This relates to mechanical, electrical and RF aspects.
In a machine with moving parts, there is always the risk
that somebody gets hit or squeezed by any of these parts.
In this facility, with the 30 rpm azimuth positioner which
can carry very large radomes, the gimbal positioner on
which radar antennas need to be mounted, etc., such risks
need to be carefully considered. Through design,
instructions and training this risk needs to be minimized.
Several hardware measures have been included in this
facility to increase the personnel safety.
Emergency stop buttons are included in three locations:
one near the elevation positioner, one near the door and
one outside the chamber, typically near the control
computer.
Also a switch is connected to the door, which disables
any positioner movement as soon as the door is opened.
This will prevent that anybody not familiar with the
facility, who could enter the facility unintended, cannot
get hurt by any moving parts.
Further a shielded window is installed in one of the
facility walls, as well as a video network camera inside
the facility. Thus the operator can easily make a final
check before starting the measurement. The camera can
be accessed through any computer on the network, so that
one can also have a regular look inside the facility for
long unattended measurements.
From the operational and health point of view carrying
and handling heavy and large objects, the facility is
optimized by having a very large door of 4 m wide, a
single step of only 5 cm from the outside to the inside of
the facility (walk-on absorbers) and by having the
installation platform at 80 cm height.
In regard to the electrical safety, the standard national and
international electrical wiring and installation standards
are followed.
In regard to RF safety, the transmitted power is very low
(less than 50 mW). In addition, the facility is typically
build inside a shielded chamber. This is primarily to
prevent interference from weather radar signals from real
aircraft in the vicinity of the facility, or to prevent the
signals from the facility to interfere with weather radar
signals from real aircraft, but also lowers the radiation
outside the facility to undetectable levels.
5. Test Results
First the facility has been tested on stability and
reproducibility. This means that all 45 antenna / gimbal
combinations have been measured repeatedly, and
variation in the angles of the beam peak as well as in the
maximum power level have been compared.
Repeatability in beam peak angle has been shown to be
better than ± 0.1 deg. Note that the power variation of the
beam peak within this angular range is only ± 0.02 dB, or
less than ± 0.5 %.
Repeatability in power level at the beam peak has been
shown to be better than ± 0.05 dB, or ± 1 % between the
reference measurements with which a radome test is
started and the final reference measurement after all
radome measurements are finished. Note that up to 14
hours can be between these two measurements for a large
radome.
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