Radio frequency interference analysis of camera modules and antennas in smartphones

As the size of mobile devices decreases and the number of cameras in the system increases, high-speed data transmission from the camera module causes neighboring Wi-Fi antenna performance degradation. In this paper, we analyze the radio frequency interference (RFI) between the flexible printed circuit board (FPCB) of a camera module and the neighboring antenna using active scattering parameters (S-parameters) extracted using a 3D full-wave electromagnetic simulator. Return loss for the active S-parameter of an antenna (S11) can be used to estimate the performance degradation coming from RFI noise sources. Design guidelines are suggested on how to design and place high-speed signal lines near a Wi-Fi antenna to reduce performance degradation. Also, a differential signaling method reduces RFI, compared to single-ended signaling. We suggest that designers replace meander line transmission line structures (used for skew compensation) with a trombone structure. The active S-parameter results are also confirmed by evaluating the radiated electric field (E-field) and coupled voltage levels on the antenna. © 2019 Institute of Electronics and Information Engineers. All rights reserved.