The George Green Institute for Electromagnetics Research | University of Nottingham




		The George Green Institute

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Facilities

The GGIEMR has a measurement lab which is primarily used for validating our numerical models and to help in the generation of new modelling techniques. The two major pieces of equipment in the lab are a GigaHertz transverse electromagnetic (GTEM) cell and an anechoic chamber or screened room. These are supported by various pieces of equipment to generate and measure electromagnetic waves.
GTEM Cell. A GTEM cell is used to create a uniform electric field over a broad bandwidth in a shielded environment and can be used for either immunity or emissions testing. The GTEM cell consists of a tapered rectangular transmission line with impedance of 50Ω (see picture). At the apex of the cell there is a standard 50Ω connector and the cell is terminated with both a resistive load for currents and absorbing material for EM waves. The GTEM Cell in the GGIEMR lab is manufactured by ETS-Lindgren and full specifications can be found on their website. it can be used for radiated emissions testing over the frequency range 9kHz to 5GHz and for radiated immunity testing over the range DC to 20GHz, however the frequency range is actually limited by the equipment with which the GTEM is associated.

Anechoic Chamber. Anechoic chambers or screened rooms are used to isolate the electromagnetic environment in the chamber from the external environment. This serves two purposes, firstly the results of measurements within the room are not affected by external influences and secondly the fields generated within the chamber do not affect the external environment. The isolation is provided by metallic walls, however this also results in reflections causing modes within the internal electromagnetic field. In order to overcome this, the walls are lined material to absorb the radiation, causing the electromagnetic fields within the chamber to resemble those in an open area test site. The chamber in the GGIEMR lab uses ferrite tiles as the absorbing lining. These tiles are rated over the frequency range 30MHz to 1GHz, however as with the GTEM the useful frequency range is also dictated by the associated equipment