Wideband and High-Isolation Properties of Power Bus Structure by the Combination of Thin-Film Embedded Capacitor and Planar EBG Structure

Power bus structure in a printed circuit board (PCB) is an influential design parameter in mitigating power/ground fluctuation and radiated emission for high-speed digital circuits. The power bus is ordinarily composed of two solid planes separated by dielectric insulator in a multilayer PCB. Recently, it has been reported that an electromagnetic band-gap (EBG)-type VDD plane is effective for suppressing radiated emission for mixed-signal applications or high-speed digital applications. However, the EBG-type VDD plane often induces large power/ground bounce due to the return current discontinuity. On the other hand, the solid-type VDD and ground plane with a thinner dielectric insulator makes wide band property of the power supply impedance by eliminating the power/ground resonances. However, even adopting an insulator thickness of 16 um, the S21 property was still around -50 dB or so. In the present work, the power bus structure with wideband and high isolation properties of around -80 dB or more has been explored by the combination of thin-film insulator and planar EBG structure.