Suppression of Common-Mode Radiation and Mode Conversion for Slot-Crossing GHz Differential Signals Using Novel Grounded Resonators

An asymmetrical grounded resonators technique to suppress the common-mode radiation (or electromagnetic interference) and mode conversion caused by the slot-crossing differential signals is proposed. The grounded resonators can be implemented on printed circuit board or package substrate without additional cost by just designing open stubs with shorting via connecting to the reference plane. The design theory based on the transmission line model is developed to estimate the physical length and effective bandwidth of the grounded resonators. In a fabricated example, the measured common-mode passband is from 2.21 to 3.35 GHz with a fractional bandwidth of 41%. Meanwhile, with the integrated grounded resonators, the differential-mode signal can still maintain good signal integrity. The reductions of the mode conversion and the common-mode radiation are also investigated. It shows that the frequency range of more than 5-dB improvement is consistent to the designed common-mode passband. The effectiveness of this novel noise mitigation approach is well validated by both simulation and experiment.