New Technologies for EM Simulation
New Technologies for EM Simulation:
What the SI Engineer Needs to Know but Was Afraid to Ask
This is a recording of a talk given by Dr. John Dunn at the DesignCon 10 conference in Santa Clara, California in February, 2010.
EM Simulation has become a vital tool for the practicing signal integrity (SI) engineer. The available software packages are getting more and more powerful, allowing for the simulation of more complex problems. Part of this speed up is of course due to the increase of raw computing power. What is less well known to the average engineer is that powerful new mathematical algorithms have also contributed to this speed up in computation. The purpose of this talk is to explain how these algorithms work in a way that is intelligible to the SI engineer. The talk looks at three areas where new mathematical algorithms have helped in speeding up EM Simulators.
- Iterative Matrix Methods for EM Planar Solvers: After reviewing how normal moment methods work, for example EMSight and AXIEM, predictions are made about how large a problem can be solved ten years in the future. The predictions are based on the assumptions that Moore's law will continue to hold true, and that the direct, matrix solvers in use today continue to be used. The discussion then shifts to compressed, iterative solvers. These new techniques allow much larger problems to be solved. Again, predictions are made for ten years out. It is argued that approximately 1 million unknowns should be possible on a modest machine. Some of the challenges facing developers are also discussed.
- Parallel Processing and Finite Element Methods: In this section of the talk, we examine the different types of parallel processing methods being tried in 3D finite element solvers. The most difficult of these is the spatial decomposition method in which a large problem is split up into different regions. The matrix for each region is sent to a different processor, and the resulting problem is solved on several computers. We discuss some of the challenges in efficiently carrying out this process. Finally, predictions are given for the capabilities of these methods in ten years time.
- Automatic Frequency Sweeping and Rational Approximation: These techniques allow the simulator to solve at fewer frequencies and yet come up with an accurate answer over the desired frequency range. The methods are also used for shipping S parameter data sets to Spice in an efficient manner. We discuss the issue of passivity, which is one of the biggest challenges for these techniques.
The entire talk lasts 3 1/2 hours. It is broken up into seven files for ease of downloading. There also is an overview video lasting 5 minutes to quickly show the highlights of each section.
- Part 1: An Overview of EM Simulation for Signal Integrity
- The types of EM simulators used in SI
- Moment methods, finite element methods
- Built in EM in circuit simulator line models
- Part 2: How a Planar Simulator Works
- The moment method and meshing
- The Green's function and building the matrix
- The time to fill and solve the matrix with a direct solver
- Part 3: Solving the Matrix and Predictions of Future Capabilities
- Mr. Carl Gauss and the N3 solve
- Moore's Law
- Predictions of problem size in ten years for the direct solver
- Part 4: Fast, Iterative Methods for Planar Solvers
- The Idea of Fast Methods
- An Analogy With Image Compression
- Predictions of problem size in ten years for a compressed, iterative solver
- Part 5: Issues When Using an Iterative Solver
- The Condition Number of a Matrix
- Poor Conditioning at Low Frequencies
- Part 6: The Finite Element Method and Parallel Processing
- Parallel Processing Means Many Things
- Splitting Up a Problem Spatially
- Predictions of Problem Size Ten Years From Now
- Part 7: Fast Frequency Sweeping and S Parameter Extraction
- Early Efforts at Frequency Sweeping
- Rational Approximation and Vector Fitting
- Exporting S Parameters to Spice
The talk is in the customer downloads area. There are five downloads total. They are: trailer.zip, part_1_and_2.zip, part_3_and_4.zip, part_5_and_6.zip, and part_7.zip.