Novel absorptive design of common-mode filter at desired frequency band

An absorptive common-mode filter (A-CMF) using mushroom-like structure will be proposed to embed in a four-layer PCB. In this structure, common-mode (CM) noises will be absorbed by a resistor, which means that the transmitted and reflected noises will both be suppressed. The proposed structure is invented and implemented based on an equivalent circuit model, for which modeled elements will be derived to achieve a high-efficiency absorption at the desired frequency. In this paper, the absorption frequency is chosen as 2.4 GHz. The simulated and measured results will be compared and discussed. The measured absorption percentage can reach up to 96% and the size of this A-CMF is merely 8.65 × 2.5 mm ² .