Signal integrity simulation has been turned inside out with electromagnetic field simulation. Instead of solving the circuits first and the electromagnetic physics later – the way it used to be done – modern simulation has placed physics-based solvers in the foreground, supported by circuit and system simulation. Advanced signal integrity analysis has grown from the creation of HFSS to the automated electronic assembly simulation of today.
We spoke with Lawrence Williams, director of product management at Ansys – the owner of Ansoft – to get an understanding of new developments in signal integrity simulation. He noted that all electronic design is fundamentally based on Maxwell's equations, so solving the equations directly would one day become the basis for the highest performance design. “That day is today,” said Williams. “Electromagnetic simulation of entire electronic systems can now be performed from a layout assembly. Advanced numerical methods, high-performance computing, new technologies for handling massive EDA data in an automated way, and multi-physics for determining thermal and stress effects have combined to make this powerful, advanced electronic design method possible.”
He noted that organizations are streamlining their processes to include this rapid, accurate simulation, supported by strong executive buy-in – a development Williams hadn’t expected. “A CTO can recalibrate his entire team by setting a 10x design turnaround goal, and automated simulation can ensure that the team will meet the challenge.”
Maxwell’s Equations – The Past Becomes the Future
The idea of incorporating Maxwell’s Equations in signal processing is an old idea that has become new again. “Ansoft was founded on the vision that all electronic design is fundamentally based on Maxwell's Equations, so solving the equations directly would one-day become the basis for the highest performance design,” said Williams.
In the past, Maxwell’s Equations were shelfed in favor or trial and error, since the equations were cumbersome. That changed with computer advances. “They can be complex to solve. We usually avoid solving them and instead we use abstractions. Even Ohm’s law,” said Williams. “You could track the trajectory of every electron flowing through a resister, but in some cases, you don’t want to.”
One of the shifts in recent years came from progressive miniaturizations, where multiple circuits are crammed into small spaces. “Look at the iPhone. We crush those components close to each other. Signal processing is pushed into a small space, and it doesn’t behave conveniently at high frequencies and high speeds,” said Williams. “Before things were so fast or close you didn’t have to pay attention to Maxwell’s Equations. But now you