RFI Improvement of MIPI C-PHY CDR Signal for Stub Filter Using Transmission Line Structure

As the available area for mounting components in mobile phones becomes smaller, the radio frequency interference (RFI) between the camera MIPI and the Wi-Fi Tx antenna increases. In this paper, we propose a stub filter designed and implemented on the camera MIPI transmission line in the PCB of a mobile phone to cancel noise in the Wi-Fi 5GHz band. Through full 3D EM simulation, we compared H-field of 3D EM simulation, S-parameter, TDR, and eye-diagram data with and without Wi-Fi 5GHz Tx RFI. The S-parameters, TDR characteristics, eye-diagram data with and without Wi-Fi 5GHz TX RFI and the signal margin measurement at Wi-Fi 5GHz Tx RFI through CDR sweep test were performed by a real SET. Simulation results and real measurement results show that our proposed stub filter structure achieves at least 2dB signal integrity improvement when RFI is present.