A Real-Time Time-Domain EMI Measurement System for Full-Compliance Measurements According to CISPR 16-1-1

Abstract

Time-domain electromagnetic interference (EMI) measurement systems allow measurement time to be reduced by several orders of magnitude. In this paper, a novel real-time operating time-domain EMI measurement system is presented. By the use of several analog-to-digital converters, the dynamic range requested by international electromagnetic compatibility (EMC) standards is achieved. A real-time operating digital signal processing unit is presented. The frequency band that is investigated is subdivided into several subbands. The EMI signal of the complete frequency band is digitized. By a digital down converter, each subband is shifted toward its baseband and low-pass filtered. The low-pass filtered signal is down sampled. The down-sampled signal is processed by a short-time fast Fourier transform. The obtained spectrogram is processed by a parallel implementation of peak, average, and quasi-peak detectors. The dynamic range of the system has been investigated. A comparison of the digital signal processing to the analog signal processing of an EMI receiver is shown. Measurements have been performed in the frequency range 30 MHz to 1 GHz. Such a system can fulfill the international EMC standard CISPR 16-1-1. By the parallel simulation of several thousand EMI receivers, the measurement at several thousand frequency bins can be performed simultaneously. Due to this benefit, the measurement time can be reduced, and further investigations on a device under test can be performed. These investigations are full characterizations, as well as full scans in the final detector mode, which is especially of benefit for highly unstationary emitting devices.