Multi-gigabit serial link emissions and mobile terminal antenna interference

Future mobile terminal digital interconnections are introducing spectrum components in cellular frequencies in an increasing manner. Control of interconnection impedance and common mode noise introduced from them are key elements for robust device design. Electromagnetic coupling from multi-gigabit serial links used for display and camera data transmission in mobile device to positioning and cellular wireless communication receivers depends mainly on common-mode content of serial link signal, and on common-mode coupling strength between the serial link interconnection and cellular receiver antenna. Frequency spectrum of common-mode component of serial link output voltage and current are determined by simulations or measurements, and 8-port S-parameters are used in calculations of induced disturbance power coupled to cellular receiver. Minimum required common-mode attenuation was found to be typically -60 dB.