The EE Department is fortunate to have a spherical near field antenna measurement facility, believed to be the only facility of its kind in a UK university. This was supplied by MI Technologies, Atlanta, an offshoot of Scientific Atlanta, and is used to measure the radiation pattern of antennas in order to determine their gain, directionality and other key properties. This type of instrument has many applications including radio communications and radar.
The instrument operates using a spherical near field scanning technique in which measurements are made by scanning antennas over a complete spherical surface and then using a mathematical transform to calculate the expected behaviour at a large distance from the antenna, the so-called far-field. This allows considerable versatility in the measurement of a wide range of antenna types in a small space, and is a facility that is usually only available in industry. Antennas of up to 1 m in length and 60 kg in weight may be measured over a 2 to 40 GHz range. A screened room is used in order to reduce interference from external signals, in which 100 dB of suppression, to 40 GHz, is achieved. The room is lined with absorbing material (RAM) to reduce reflections that would otherwise result in pattern measurement errors.