Emi/rfi filter including a ferroelectric/ferromagnetic composite

Abstract

An EMI filter ( ) that makes use of a ferroelectric-ferromagnetic composite, member, or slab ( ) in connection with capacitive and inductive elements. The geometrical structure of the filter ( ) is such that the mutually orthogonal electric fields and magnetic fields generated by the capacitive and inductive elements penetrate the volume of the composite ( ). In some designs, capacitive plates ( ) are split to avoid setting up eddy currents in the plates ( ) which oppose the penetration of magnetic flux through the composite ( ). Various structural designs can be provided to define the capacitive elements and the inductive elements in different configurations relative to the composite to satisfy the desirable requirements. One particular low-pass design includes providing a slab ( ) of the composite with plates ( ) on opposite sides of the slab ( ) that define capacitors, and a conductive strip ( ) wrapped around the slab ( ) and electrically connected to the hot capacitive plates ( ) that define the inductor. This basic configuration can be extended to a cylinder ( ) made of the composite, where a ground plane ( ) is provided on one surface ( ) of the cylinder ( ), and the hot capacitor plates ( ) are provided on the other surface ( ) of the cylinder ( ), where a conductive strip ( ) on the other surface ( ) defines the coil. A multi-layer filter ( ) can be provided that includes layered substrates ( ) where metallized vias ( ) extending through the substrates ( ) define a coil, and ground planes ( ) and capacitive plates ( ) on alternating substrates ( ) define the capacitive elements.