Improved Techniques and Instrumentation for EMC Measurements

This paper presents a survey of improved measurement techniques, instrumentation, and data presentation for accurate, meaningful evaluation of electromagnetic compatibility (EMC) of electronic systems and sub­ systems. These techniques and instrumentation were developed as alternatives to conventional, MIL-STD461/462, measurements which recommend screen room testing with conventional antennas. These alterna­ tives are used to accurately measure and quantify EM emissions from electronic equipment and/or for estab­ lishing standardized EM susceptibility test fields. Dramatic improvement (worst case errors of 1 to 3 dB compared with 40 dB from conventional screen room measurements) have been demonstrated. The techniques described in the paper include: 1) low-Q or under­ ground enclosures, 2) mode stirred, shielded enclo­ sures, 3) specially designed, shielded, transverse electromagnetic (TEM) cells, 4) broadband field probes capable of measuring complex average or peak fields without causing perturbation, and 5) time and ampli­ tude statistics for characterizing the measured data.