Satellite operators are using ever more complicated antennas to provide spot beams and increase satellite capacity. Engineers need a way to test these antennas on the ground. The European Space Agency has constructed the Compact Payload Test Range in its ESTEC technical center in Noordwijk, the Netherlands to test satellite antennas.
The test range consists of a Faraday cage to block all external RF signals and anechoic foam cladding absorbs RF inside the test range. ESA recently installed a state-of-the-art Near Field Scanner at test range to measure electromagnetic fields close to a test antenna. Multiple near field measurements can be used to calculate the far field antenna pattern. This makes it possible to measure large antennas (up to 8m in diameter) over a frequency range of 400 MHz to 50 GHz.
A picture of the facility is available in the ESA release Zone of silence: Testing satellite antennas. The first assignment for the new equipment will be to characterize the radiated performance of the next Galileo satellite prior to their launch later this year.
This near field technique sounds similar to the method used to verify broadcast antenna performance I wrote about many years ago; see my January 1996 RF Technology Column showing a near field probe being used to measure an Andrew slot antenna.
Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.
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