An Embedded Common-Mode Filter and Mixed-Mode Scattering Parameters for the MIPI C-PHY Interface

Abstract

This article presents an embedded common-mode filter (CMF) for the Mobile Industry Processor Interface C-PHY signaling standard and proposes a definition of mixed-mode scattering parameters for the standard. The proposed mixed-mode scattering parameters for C-PHY separate components of signals of C-PHY that have different properties and are useful for designing circuits (located between the transmitter and the receiver) for C-PHY that maintain signal integrity well. Simulations and measurements indicate, from the perspectives of the time and frequency domains, that the CMF suppresses common-mode noise and meanwhile maintains signal integrity. Therefore, the CMF can be used to reduce radiation that adversely affects wireless systems. To the best of our knowledge, the CMF presented in this article is the first CMF for C-PHY that is not based on the idea of coupled inductors of a common-mode choke. Since the proposed CMF can be implemented using the printed circuit board process, it can be more cost-effective than previous common-mode chokes for C-PHY. The proposed mixed-mode scattering parameters enable easy evaluation and design of CMFs and other circuits for C-PHY.