Datapath Q Series, Instructions For Use Manual, Page: 90 / 104

Construction Details Q-Series
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Skew
If the satellite position is not on the same longitude as the transmission site, the polarization
plane will be tilted, or skewed. To compensate for this, the feed horn is rotated for the specific
satellite. The Q-Series feed horn can rotate 190° clockwise as seen from the front.
Figure 53: Rotating the Feed Horn to Compensate for Skew
Antenna Details
The antenna concept used is called dual reflector, dual optics or Gregorian offset antenna.
This is because the antenna has two reflectors - the big main reflector and the smaller subre-
flector. The main advantages compared to the more common prime focus offset antenna
design concept (feed illuminates the main reflector directly) are:

Freedom of design for optimization (shaped reflectors). Higher gain, that is high aper-
ture efficiency (80%).

Lower side lobe levels.

Better cross polarization discrimination.

A more compact geometry, making it suitable for folding/stowing.
The main antenna functions are:

Concentration of radiated super high frequency (SHF) rays into a very narrow beam -
the subreflector concentrates the rays from the feed horn and illuminates the main
reflector in a very controlled way. The main reflector concentrates the beam even
more.

Reception of signals - the main and subreflectors form an optical system that direct
SHF rays coming from the space segment into the feed horn in a controlled way.

Discrimination between different polarization of in- and outbound SHF rays.

Mechanical structure defining the relative position of the feed horn, subreflector and
main reflector. The most noticeable part is the feed arm holding the feed horn and the
subreflector.
Recycling Information
The Q-Series is a complex unit and it is difficult to disassemble for a non professional.
When the system is taken out of service, pay attention to proper disposal of the equipment
according to local regulations.