A novel and cost-effective method to suppress GHz common-mode radiation for slot-crossing differential lines

By placing two asymmetrical open-stubs (ground resonators) beside the slot-crossing differential line, the radiated emission induced by common-mode noise is greatly reduced around the interested frequency. According to the proposed equivalent circuit model and the design formulas, these ground resonators can provide a shorting path for the common-mode return current around the resonant frequency and prevent the noise from exciting the antenna-like slotline. Based on the proposed concept, the solution board and the reference board are both fabricated by typical PCB process. The experimental results demonstrate that the normalized total loss of the common-mode is effectively reduced by the connected ground resonators around the designed frequency range. Also, the simulated results indicate that the radiated emission caused by the slot-crossing common-mode noise is greatly reduced more than 5 dB from 2.34 GHz to 3.55 GHz. It is a cost-effective solution to reduce the radiated emission from the slot-crossing common-mode noise around GHz frequency range on high-density package or PCB.