EMI reduction on high-speed PCB using electromagnetic bandgap structure

The need for high-speed printed circuit board design whilst maintaining signal integrity and EMC standards have increased over the years in the modern integrated circuitry field. The use of electromagnetic bandgap structures (EBGs) have been demonstrated to provide excellent reduction of electromagnetic interference (EMI). In this study, a three by three planar of spiral, with and without patch were designed, simulated and fabricated on a low-cost FR4 substrate with permittivity of 4.3 and thickness of 1.6 mm. The designs of spiral EBGs with and without patch have the dimensions of 36 mm x 36 mm covering 9 unit cells. The performance of the designed EBGs were simulated and measured experimentally, and it was found to be in acceptable agreement. It was found that the spiral EBG without patch experienced a bandgap that covers from 4.5 to 6.3 GHz by using a dispersion diagram. Conversely, the bandgap for the spiral EBG with patch structure was found to be from 4.5 to 7.8 GHz with wider bandwidth. Owing to the desirable results demonstrated by the spiral EBG design with patch, it was then integrated into the high-speed circuit design to suppress the EMI emitted by the board. In this work, two low and three high-speed PCB designs were fabricated to track the desired EMI levels above 4.5 GHz. The third design of the high-speed PCB emitted the highest radiation emission (4.54 GHz) was selected for integration. The spiral EBG with patch structure successfully suppressed the EMI that occur at 4.54 GHz. Its effectiveness further suggests that the proposed EBG spiral with patch structure design is appropriate for EMI suppression that may occur from 4.5 to 7.8 GHz