Noise cancelling algorithms for FPGA-based time-domain EMI measurements in real-time

Traditionally measurements of electromagnetic interference (EMI) are carried out in frequency domain resulting in long testing times according to the frequency range and resolution in frequency. By applying time-domain technology EMI measurements can be done now in real-time for a broad frequency range of several hundred Megahertz. This paper presents advanced strategies with real-time capability for adaptive noise cancellation based on a powerful hardware platform to enable EMI measurements in the presence of electromagnetic ambient noise on open test sites. Frequency domain and time-domain adaptive filtering are compared. Two adaptive filter algorithms are enhanced in respect of implementing the noise cancelling algorithm on field programmable gate arrays. Ensuring a continuous high data-throughput by an optimized digital signal processing a real-time noise suppressing method is shown for frequency bands of over 125 MHz bandwidth at once.