What kind of testing does the Antenna Test Facilities do?
The two Facilities perform the same kind of testing and tests are set up on the similar basis. A feed horn linked to a set of parabolic and hyperbolic reflectors is used to illuminate the object under test with a uniform test field .
By varying the feed horn position relative to the test chamber's focal zone the signal wave front shifts from its standard alignment. This means the test item's uplink/downlink performance can be measured in terms of satellite communication with ground stations in different locations on Earth's surface.
Key measurements include checking an antenna's main beam alignment. Radio waves are EM radiation just like visible light, and they behave in the same way. An antenna is designed to focus radiation into a main beam in the same way as a flashlight does. The main beam must achieve the designed concentration and pointing direction.
Tests also characterise an antenna's side lobes. Not all the light from a flashlight goes into the main beam, a small amount radiates to the side. The same is true of antenna radio waves, but the amount must be compliant with design requirements otherwise it can lead to interference.
The antenna should work over a certain minimum and maximum frequency range and should not be sensitive to other frequencies beyond it.
The antenna efficiency is also a key concern: testing involves measuring how much power goes into the system and how goes in the desired direction.
Tests are performed on individual antennas as well as antennas integrated with other antennas or subystems because typically their resulting EM response will have been altered by this integration process.
Radio reflectivity tests are performed in some cases, measuring EM reflections of test items in different directions – often referred to as radar cross section (RCS) testing. This can be a useful test for assessing candidate materials for lightweight antenna construction.
As well as testing antennas and payloads, the Facilities are also used for assessing the feasibility of new types of measurement tools and techniques, often liaising with external industrial antenna laboratories as they perform tests related to ESA projects.
Last update: 29 September 2009
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