Influence of RF EMI filter structures on high speed digital signals

Progress in electronic component production has enabled a scaling-down of circuit layouts over the past years while realizing similar functionalities. Driven by the ldquoneed for speedrdquo, data transmission rates and therefore signal frequencies have increased throughout electrical circuits in new applications. Both trends mean that circuit operation becomes more sensitive with respect to signal integrity. To suppress unwanted signals, electromagnetic interference (EMI) filters are in use. This article deals with the influences of circuit impedances on the signal, as signal shape is crucial for high speed digital signal transmission. In addition to filter elements, connecting lines are taken into account. It is shown that filters can be improved by an extended view in comparison to past methods. The ldquonaturalrdquo description for such filters, frequency domain, may provide a link to time domain, which is focused on for characterizing digital signals.