A realtime time-domain EMI measurement system for measurements above 1 GHz

Emissions measurements performed in time-domain using ultra-fast analog-to-digital converter and real-time digital signal processing allow to reduce the measurement time by several orders of magnitude. In this paper a novel real-time operating time-domain EMI measurement system is presented for the frequency range up to 3 GHz. For the frequency range up to 1 GHz a noise figure about 8 dB has been achieved, while above 1 GHz the noise figure is below 6 dB. The system uses a multiresolution analog-to-digital converter system. Above 1 GHz an ultra-broadband down converter system with 325 MHz bandwidth allows to perform ultra-fast emission measurements. In comparison to existing heterodyne systems the measurement time is reduced by about a factor of 60 for 1 MHz IF Bandwidth and by a factor of 2000 for an IF Bandwidth of 120 kHz. Measurements have been carried out in the frequency range 30 MHz - 3 GHz and have proven, that the system provides enough sensitivity for measurements over the complete frequency range.