Wideband narrow pitch via electromagnetic bandgap structure for suppression of P/G noise coupling to signal in SiP

Abstract

The system in package (SiP) is prevalent for mobile application due to its small system size and short development time. And highly diversified wireless standards demand more functional SiP which can support a number of wireless standards. But it is relatively hard to isolate digital signal and RF signal in SiP. Therefore, isolation method for RF signal is essential to guarantee system performance. The power/ground nose is becoming a major problem in SiP as clock frequency and power consumption increase. The generated power/ground nose in the power/ground plane couples to a RF signal via when the RF signal path changes its reference plane. The power/ground nose coupling to RF signal traces causes problems for sensitivity and ultimately degrades the system performance. Therefore, the power/ground nose coupling to RF signal has to be suppressed to guarantee the system performance. In order to suppress the power/ground nose coupling during the RF signal via transition, the RF signal via should be isolated from the noise propagation in power/ground plane. One of the methods to provide isolation is using EBG structures which are periodic structures that provide excellent suppression of noise above hundreds MHz where decoupling capacitors fail. Hence, the power/ground nose coupling is suppressed when signal via is surrounded by EBG structure. In this research, narrow via pitch EBG structure with wide stopband and its analytical model for stopband prediction are proposed. The design approach was enabled by increasing the EBG density, which means increasing the number of EBG cells per unit area. And proposed EBG structures have small area and significantly extended noise isolation bandwidth compared to conventional EBG structures without additional thin film or high DK film. Although mushroom type EBG structures are used, the narrow via pitch EBG structure is vertically stacked, instead of 2-D planar disposition. And the power/ground nose coupling to a signal wit...