Ultra-wideband noise suppression of power supply noise by combining mushroom and planar type EBG structures

Power supply noise spectra generated by CMOS digital circuits has been shifting to the higher frequency range, as the clock frequency of CMOS digital circuit is becoming faster year by year. Therefore, a new electromagnetic band gap (EBG) structure is strongly required to prevent the wide frequency noise from DC to high frequency components so as to apply to any operating frequencies of CMOS digital circuits and RF circuits. In this paper, a new EBG structure with ultra-wide stop band has been proposed by combining two kinds of EBG structures, i.e., the mushroom type and the planar type EBG structures in a printed circuits board (PCB). This EBG structure consisted of 4 conductive layers. By placing two power supply layers and two ground planes alternatively, two mushroom type EBG structures were constituted vertically in the 4 conductive layers. The unit cells with the same potential were connected each other using via holes. In addition, the top conductive layer provided the planar EBG structure with longer bridge line than the conventional EBG structure. The new EBG structure has been found to have a ultra-wide stop band property by measurement and simulation.