Electromagnetic Interference Reduction Filters

Abstract

This paper presents the theory and application of lumped-image parameter reactive filter networks, absorptive-type filter networks, and combined absorptive-reactive filter networks as conducted electromagnetic interference reduction circuits. A comparison of the passband characteristics by specific examples is given for filter configurations of the pi, T, absorptive, and absorptive-reactive type under implementation conditions of a fixed source impedance and a varying load impedance as encountered when filtering prime power sources feeding ac to dc converters. This paper illustrates the problem the design engineer faces when applying the usual data given in filter catalogs. The filter characteristics are presented for 50-ohm resistive source and load conditions because of MIL-STD-220A quality control testr equirements. A test configuration is recommended to determine the admittance transfer of a filter network, indicative of the networks performance characteristics under application conditions.