High speed PCB designing for EMC in biomedical systems

Abstract

High speed data (Gbps) demand for next generation high performance computing devices makes electromagnetic compatibility (EMC) and signal integrity (SI) crucial for modern medical product design. EMC and SI technologies on the printed circuit board (PCB) are the bottlenecks to achieve such high data rate. EMC and signal integrity are major challenges in PCB, which might itself inject switching noises, thereby decreasing the EMC performance of electronic equipment, especially sensitive equipment requiring high precision, such as medical instruments. In this research, we focus on four major problems in PCB, i.e. fiber weave effect, split plane effect, SSN and finally EMC problem. Four solutions are proposed for reducing these effects on PCB level and adversity effect to increase the EMC performance of the system. The first solution for reducing the phase difference between the differential pair is explored, studied, and simulated on IBIS-AMI models and a solution is proposed. Fiberglass and epoxy-based dielectric substrates are ubiquitous in manufactured printed circuit boards. Their construction usually involves various woven fiberglass fabrics saturated with epoxy resin. These two materials have different electrical properties; hence, as the data rate increases and structure feature-size decreases, the fiber weaves in the substrates can have profound impacts on the effective dielectric constants of printed circuit boards, which can cause unforeseen degradations in signal integrity. This work proposes a systematic way of modeling the fiber weave effect on high-speed interconnects over low-cost substrates, and also presents a statistical analysis of the impact of the fiber weave effect on intra-pair skew of differential microstrip lines. The second solution is proposed to overcome the split plane crossing problem for high speed interconnects. It is a geometry based method which is very effective during slot crossing.