Requirements and solutions for emission measurements in time-domain according to international EMC standards

Measurements of electromagnetic interference in time-domain allow to reduce the scan time by several orders of magnitude, in comparison to automated scans performed by the tuned selective voltmeters, which are known as EMI receivers. Spectrum analyzer are used for fast sweeps to get an overview. Such analyzers can perform fast sweeps or scans over large bands. With the update of CISPR 16-1-1 Ed 3.1 the requirements for time-domain EMI measurement systems have been described. These time-domain EMI measurement systems are using the short-time fast Fourier transform to simulate a set of up to 4000 receivers simultaneously. A major requirement is the gapless aquisition during the dwell time. In this paper the requirements and solutions for time-domain measurements are discussed. A major requirement is the gapless processing of the input signal. This requirement is mandatory to detect over the observation time an isolated impulse. Further requirements are IF-filter bandwidths and indication in the various detector modes for different pulse repetition frequencies as well as the dynamic range. In this paper also the requirements regarding calibration are discussed. It is shown that time-domain measurement system can be used for the accurate measurement for a full compliance final measurement and also for ultra fast sweeps, replacing spectrum analyzers. In both cases the sweep and scantimes are reduced.