Patent ID: 8847705

Claim:
A common mode filter, comprising: a lumped-constant differential delay line formed by arranging inductors, being passive series elements, and capacitors, being passive parallel elements, in a ladder-shaped differential four terminal network composed of the passive series elements arranged in series in each differential line and the passive parallel elements arranged in parallel between the differential lines, wherein two of the capacitors having same values as each other and forming an equivalent capacitance for the passive parallel elements are connected in series; and a passive two terminal network including only resistors, or a parallel circuit of additional inductors and the resistors, said resistors connected between a connection point of the two capacitors connected in series and a ground potential to constitute a returning path of common mode current to the ground potential to generate an attenuation of the common mode noise by the absorption at said resistors in the passive two terminal network, and wherein the lumped-constant differential delay line and the passive two terminal network are formed as differential delay elements of one section, the differential delay elements are arranged in plural in series in a ladder shape, thus forming a plurality of sections.