Radiated emission measurements with an ultra-fast time-domain EMI measurement system

Traditionally emission measurements are performed in frequency domain and take a long time for a single scan. Pre- and final scans are performed to reduce the time for the characterization of the device under test. Emission measurements in time-domain can reduce the measurement time for a single scan up to a factor of 4000. In this paper test procedures for radiated emission measurements are presented. An initial scan is proposed to determine the minimum dwell time that is required to get reproducable measurement results. If the dwell time that is required by the device under test is much smaller than the settling time of the quasi peak detector an enhanced pre- and final scan is proposed. However if the required dwell time is larger than the settling time of the quasi peak a full maximization is proposed. The procedures have been applied in an anechoic chamber in the frequency range 30 MHz -1 GHz. By such measurements the characterization of highly unstationary signals has become available. Automated measurements with high reliability can be performed.