Comparison between anechoic chamber and open area test site through analyses with loop antennas

Introduction Electromagnetic compatibility (EMC) is the branch of electrical sciences which studies the unintentional generation, propagation and reception of electromagnetic energy with reference to the unwanted effects (Electromag- netic Interference, or EMI) that such energy may induce. The goal of EMC is the correct operation, in the same electromagnetic environment, of dif- ferent equipment which use electromagnetic phenomena, and the avoidance of any interference effects. A particular definition of EMC, as given in the International Electrotechnical Vocabulary is ”The ability of a device, equipment or system to function satis- factory in its electromagnetic environment without introducing intolerable electromagnetic disturbance to anything in that envi- ronment.” The main phenomena EMC deal with are indeed electromagnetic distur- bances. First of all the conducted low frequency phenomena, that can be related to the power supply, in particular with its phase when it is AC. They can be divided in harmonics and interharmonics, signalling voltages, flickers and induced LF voltages. Also radiated LF phenomena are considered and they are mainly related to nearby power lines, buried or overhead. Con- ducted HF phenomena are typical of wires exposed to RF fields that induces a disturbance depending on the cable length, its separation from the ground reference, loops formed and any resonance effects. Radiated HF phenomena are given by nearby transmissions and can be divided in far-field or near- field, according to the distance. On the other hand there is the need to avoid unexpected emission of electromagnetic fields by the equipment under test (EUT). Indeed in most countries of the world the radio spectrum is heavily used for many kinds of traffic. Broadcasting and telecommunications are the most obvious uses, but telemetry, radar, radionavigation and space research are some other purposes. Spectrum users pay a licence for the privilege of beingallowed totransmitandreceive andinreturntheyexpect thisprivilege to be unaffected by interfering sources. For this reasons governments have 1