Large CPTR

How are the Antenna Test Facilities equipped?

Both the CATR and CAPR are shielded anechoic chambers with internal foam coatings that absorb reflected radio waves to simulate the boundless nature of space. The metal walls form Faraday cages, blocking all external signals such as TV broadcasts, airplane and ship radars and even mobile call phones.

The Facilities are both referred to as 'compact', though not strictly because of their size – the CATR is 12.5 m long by 8.5 m wide and 4.3 m high, while the CPTR is the size of a small sports hall, measuring 25 m long by 16 m wide by 11m high. Instead this term refers to a particular design feature.

Radio waves coming from a nearby source are curved like a pond rippling after a stone is thrown. Radio waves coming from great distances take the form of parallel straight lines converging on infinity. So compact anechoic chambers incorporate parabolic reflectors which are specially shaped to straighten the curvature of the radio waves, artificially creating equivalent conditions to space transmissions within a relatively small area.

The two Facilities are complementary: the CATR, which is classed as an ESA Laboratory, allows easy access and mounting of small test objects in ambient environmental conditions, and its instrumentation has a frequency range of 4 to 110 Gigahertz, with an extension to 250 Gigahertz in the process of development.

The CPTR has a frequency range of 3.5 to 20 Gigahertz and can incorporate much larger items. Officially classed as a Test Facility, the CPTR is a Class 100,000 (ISO 8) clean room. It is also designed for low cross-polar performance, meaning that very accurate measurements of communications payloads employing frequency and/or polarisation re-use can be performed.

Last update: 29 September 2009

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