ABSTRACT
Conceptually, an electrical filter network will filter out lower or higher frequency bands while passing specific bands of frequencies. The basic property of an EMI filter is usually described by the insertion-loss characteristic. The configuration of the input and output terminals of an electromagnetic interference (EMI) filter is changed through different types of measurement setups, and this fact alone complicates the measurement itself. EMI filter design engineers think in terms of attenuation, insertion loss, and filter impedance, while a regular wave filter designer thinks in terms of poles, zeros, group delay, predistortion, attenuation, and the order of the filter. EMI filter design can be accomplished in a rule of thumb fashion where estimation of losses, pole-Q frequency, and stability are all based upon experience and guesswork. EMI suppression filters for AC power lines eliminate noise entering equipment from commercial power lines or noise generated from electronic equipment that may be sharing the same AC power connection.
