Inductance Cancellation of Multiple Elements from Single Coupled Inductor


Electromagnetic interference (EMI) filters are used in many types of electrical equipment, including computers, energy management systems, and telecommunications. They play a large role in bringing device compatibilities up to federal regulations.

Problem Addressed

Coupled magnetic windings can be used to compensate for the effects of parasitic inductance in circuits and increase filter performance. However, providing coupled windings for each capacitor in a circuit can require significant real estate. Inductive impedance cancellation for multiple capacitors reduces the amount of space occupied by passive elements.


EMI filters can have coupled magnetic windings that provide inductive impedance cancellation for multiple capacitors at one time. The invented filter does this in a space efficient and elegant manner. Discrete magnetically-coupled windings nullify generated voltages due to equivalent series inductance of multiple capacitors. The capacitors can be coupled and attenuated to the circuit for a differential-mode signal or a common-mode signal. In this way, inductive impedance cancellation enables the increased performance of EMI filters with a slimmer architecture.


  • Slim filter structure takes up less space and has lower insertion loss for input signals
  • Simplifies circuit design for easier manufacturing