J. L. Herring and C. Christopoulos
5th British Electromagnetic Measurements Conference, Malvern UK, November 11-14 1991, pp 37/1-37/4.
Electromagnetic measurements at high frequencies are required in many engineering applications, a particular example being electromagnetic compatibility (EMC) compliance testing. The environment in which these measurements are performed is specified by international standards and typically it may be a screened room, an anechoic room, or an open site. Similar measurements are required for testing antennas and other high frequency devices. Each of these environments is complex especially since measurements over a wide frequency range (several GHz) are normally required. Measurement antennas can be accurately calibrated, in well understood, controlled, environments (e.g. TEM cell). However, inside a screened room, resonances, and the interactions between antennas and with the device under test (DUT) cause many difficulties in calibration, repeatability and interpretation of measurements. Hence correlation of results obtained on different sites and/or facilities is poor. This unsatisfactory state of affairs has led to the establishment of a programme of work, sponsored by the Ministry of Defence, aimed at identifying and quantifying all factors affecting electromagnetic measurements and thus contributing to better measurement standards. Nottingham University is contributing modelling expertise to this programme and the purpose of this paper is to present results from some of the investigations performed so far. The simulations were conducted using a technique known a transmission-line modelling.