Traditionally, boards have had dedicated power and ground planes that were independent from the signal planes. Because the power and ground planes were used exclusively for that purpose, they were practically continuous sheets with few, if any, perforations. The previous generation of power integrity electronic design automation tools relied on this topology by using approximations that increased simulation speed but were valid only in the case of solid power and ground planes.
The demand for high-volume, cost-reduced boards has been met with a new design paradigm called split-power ground layout where signal lines cohabit and perforate the power and ground planes. This approach dramatically reduces the layer count and cost of the board, but renders useless previous generation power integrity tools.
The power integrity solution in Agilent’s ADS 2011 Momentum solves power integrity problems that are complicated by heavily perforated power and ground planes. Unlike other power integrity tools, Momentum does not assume solid power and ground planes. It contains a full wave 3-D multilayer electromagnetic field solver that yields power distribution network impedance for an arbitrary input mixture of power, ground and signal nets on each layer. Unlike previous generation static and pseudo-static power integrity solvers (which are accurate only up to several hundred megahertz), the results from Momentum are valid into the multi-gigahertz range This enables the tool to be applied to heavily perforated boards, as well as high-frequency IC package power integrity problems.
The Agilent R&D team created this capability by enhancing the speed and capacity of the proven method-of-moment technology in Momentum. The enhancements allow Momentum to be applied to very large structures such as power distribution networks.
Traditionally, Momentum has been used for smaller RF and microwave structures where a polygon-based layout design and setup is preferred. Power integrity engineers, however, prefer to import the artwork from an enterprise board tool and then apply a net-based setup where port-to-port connections, not raw polygonal shape data, determine the electromagnetic simulation setup. For this reason, ADS 2011 now includes a signal integrity/power integrity analyzer that provides a simple net-based electromagnetic simulation setup wizard and automatic test-bench generator for typical SI/PI circuit simulations.
In addition, Momentum also now models wire bonds, the effects of frequency-dependent dielectric loss and the surface roughness of copper traces, which are important in signal integrity and power integrity design.