A New Procedure for Evaluating the Performance of the Sites for Radiation Tests or Antenna Calibration

The radiation experiments in use in the EMC tests for emission or immunity and in the calibration of the test antennas are essentially based on a specific reference site consisting of an infinite, perfectly conducting plane and a perfectly absorbing semi-space above it. Approximations of this ideal site (i. e. the Open-Area Test Sites or Alternative Test Sites) are tested by measuring the insertion loss between two calibrated antennas in a specified geometry and comparing the result with what would be obtained by calculation and computation from the ideal reference site. In so doing, several approximations and instrument uncertainties are by necessity introduced, thus imposing onto the Site a burden that is mostly originated by the imperfections of the test method. A procedure is here proposed, intended to directly compare the test site with the reference site without involvement of the measuring system. Thus, a pair of antennas with their associated equipment are rigidly moved together along the ground while recording the received signal over the frequency range of interest: any variation observed over the range covered by the motion is to be attributed to site imperfections. Various aspects of this procedure are discussed, with possible technical variations and extensions (e. g. fully anechoic chamber), advantages and limits. Experimental results are presented.