A Novel Ground Resonator Technique to Reduce Common-Mode Radiation on Slot-Crossing Differential Signals

By symmetrically placing a pair of open-stub resonators on the slotted reference plane, the radiated emission induced by common-mode noise crossing the slot can be effectively suppressed. The ground resonators provide a shorting path below the slot-crossing differential line for common-mode return current around the resonant frequency and thus avoid the noise to excite the slot line. Based on this idea, test samples with the proposed structure are fabricated on FR4 substrate. The experimental and numerical results show that the radiated emission caused by the slot-crossing common-mode noise can be effectively reduced at least 5 dB in the frequency range from 2.16 to 3.44 GHz by the ground resonators. It is a low cost and effective solution for reducing the common-mode radiation for the slot-crossing high-speed differential signals on high density package or PCB.