Theory of Simulated-Skin-Effect Filters a Thin Film Approach to EMI

The theory of a new, ceramic lowpass filter, highly effective at very high frequencies, is discussed. Its excellent performance is based on simulation of the skin effect whereby the VHF, UHF and microwave currents are forced along a thin, electrically permeable resistive film deposited inside a high-ϵ dielectric tube while a large dc current may flow through the coaxial conductor. Theory and experiment are in excellent agreement. In several respects these filters are better than cascaded filters (ferrites and dielectrics combined) which were, thus far, considered the best available. The simulated-skin-effect filter shows great promise of becoming a significant means in combatting conducted electromagnetic interference.