A Real-time Multiresolution Time-domain EMI Measurement System based on Ultra-fast High Resolution Analog-to-Digital Converters

In the past and now measurements of electromagnetic interference (EMI) are carried out by EMI-receivers operating in frequency-domain. By a time-domain EMI measurement system the measurement time can be reduced by several orders of magnitude. In this paper a novel real-time time-domain EMI measurement system that uses a hardware implementation of the Fast Fourier transform and the detector modes is described. A multiresolution Time-domain EMI system has been developed that processes the EMI Signal by several parallel analog-to-digital converters with an improved dynamic range. The signals are digitized by three 10 bit ADCs which operate at 2.3 GS/s. The obtained EMI signal with a high resolution is further processed in real-time by a decimation filter and a short time fast Fourier transform on the field programmable gate array. By this way the measurement time can be reduced by a factor of 2000 in comparison to EMI receivers and spectrum analyzers. Due to the real-time implementation auxiliary outputs that are provided by EMI receivers as well as spectrum analyzers can also be provided by a time-domain EMI measurement system. The two tone intermodulation distortion as well as the measurement accuracy of the Time-domain EMI Measurement System have been experimentally investigated in the frequency range 30 MHz - 1 GHz. The maximum deviation in comparison to an EMI receiver has been 1.5 dB.