| Popis: |
Modern printed circuit board (PCB) designs are highly complex. Within a board, there may be 25 or more thin metal layers dedicated to routing many analog and logic signals plus various power and ground supplies. Because of the high-speed signals propagating through these boards, some form of rigorous full-wave electrical analysis is attractive for identifying problems with signal integrity, power delivery or EMI. However, the massive geometric complexity of the problem is certain to overwhelm any existing three dimensional field solver. We describe a practical approach to solving these planar designs. We take advantage of the layered nature of PCBs, and, in particular, the presence of large power and ground planes within them, to make the problem tractable. Within each cavity formed by a pair of adjacent voltage supply planes, we show that a 2D wave equation can be formulated and solved using the finite element method. We then discuss how to incorporate signal traces into the model by applying a modal decomposition technique. With these basic elements in place, we are able to compute the frequency-domain network parameters for large and complicated high speed boards and packages. |
