Improvement of mode conversion for LTCC multi-layer common mode filter by twisted differential lines structure

Abstract

In high-speed differential signaling interfaces, the multi-layered common-mode filter is one of the methods used to reduce common-mode noise. But since the differential traces in multi-layer structure is not perfect symmetric. The mode conversion will occur. By using the proposed twisted differential lines architecture, the asymmetrical circuit introduced between positive and negative traces is improved, so the mode conversion can be reduced. By inserting more twisted structures in each circuit design, the suppression effectiveness of mode conversion with twisted structure is also discussed.