Signal integrity analysis of the traces in electromagnetic-bandgap structure in high-speed printed circuit boards and packages

In this paper, signal integrity analysis of traces between two parallel planes with an electromagnetic-bandgap (EBG) structure is made. It is shown that, within the stopband, the signal transmission quality is excellent, traces in the EBG structure are free from cavity resonances, and behave as regular standard transmission lines. It is shown that the high-impedance surface behaves as a solid continuous reference plane within the stopband. The impedances of the traces between the high-impedance surface and the reference planes are extracted. It is found that the extracted impedances are exactly the same as striplines with the same parameters. It is shown that the traces between the high-impedance surface and the reference planes are regular standard striplines within the stopband. In addition, a novel four-via EBG structure is proposed to broaden the stopband for simultaneous switching noise suppression in high-speed digital printed circuit boards and packages. This four-via EBG structure has a higher relative bandwidth and lower center frequency. Compared with one-via EBG structure with the same parameters, the stopband is broadened three times and relative bandwidth is increased 1.3 times, while there is very little, additional cost since there is no more change than number of vias. Two test boards with four-via EBG structure were fabricated to verify the signal integrity of the traces and the impedances extraction. Good agreements are observed between the simulations and measurements.