Guest Column | January 20, 2011

Electromagnetic Simulation: Tips, Tricks, & Tradeoffs


RF Globalnet is pleased to welcome Dr. John Dunn, a senior applications engineer at AWR Corporation and recognized expert in EM modeling and simulation for high-frequency and high-speed circuit applications, as a guest columnist. His columns tackle the key EM issues faced by the everyday engineer and EM point tool power-user alike.

The Trouble With EM — It Always Gives An Answer!
Now I know what you are thinking. How can this be a problem? As an overworked, overloaded, and overcommitted designer, I'm sure you have bigger issues to worry about than a CAD tool that (almost) always gives you an answer. The question is: Does it give the right answer? Read the article.

Understand Ports — The Key To Mastering EM Simulation
If you use an EM simulator, you use ports. No kidding! Ports are the way the EM simulator "talks" to the outside world and are the way you measure S-parameters — the "high-frequency" data that can be used in a circuit simulator. The difficulty with ports is that they are often misunderstood, and therefore improperly used inside of EM simulators. Read the article.

EM Ports — A Ground Is Out There Somewhere
As electrical engineers, we all know about ground. Along with voltage and current, it is one of the most fundamental concepts anchoring electrical engineering. But what you may not know is that ground is not used in Maxwell's equations, the physical equations that form the basis of electromagnetics. Read the article.

Understanding Ports — What's The Fuss About Deembedding?
All ports have parasitics. De-embedding removes a port's parasitics, attempting to make the port as perfect as possible in the imperfect world we live in. Sounds like a good idea, right? Well yes and no. Unfortunately, deembedding makes a number of assumptions that will lead to erroneous results if they are not understood, appreciated, and/or violated. Read the article.

The Wonderful World Of Electromagnetic Antenna Simulation
It has become popular to simulate antennas in electromagnetic (EM) simulation software. After all, an antenna is by its nature an electromagnetic beast. Its whole purpose is to emit and/or receive electromagnetic waves as efficiently as possible. Even to more experienced circuit designers, antennas can be mysterious entities, not obeying the laws of normal circuit theory. Read the article.

Voilà. An EM Simulation That Converges. But Is It Correct?
One of the most common questions I get from engineers is: "But, how do I know it's the right answer?" In many ways, this is the most fundamental question any engineer can ask when looking at the results of his or her EM simulation. After all, isn't this the essence of what simulation it is all about – getting the right answer? Read the article.

About The Author
As a senior applications engineer, Dr. Dunn develops and presents AWR training material to customers world-wide. Before joining AWR, he was head of the interconnect modeling group at Tektronix and a professor of electrical engineering at the University of Colorado, Boulder, where he led a research group in EM simulation and modeling. Dr. Dunn received his Ph.D. and M.S. degrees in applied physics from Harvard University and is a senior member of IEEE. You can contact him at

About AWR
AWR is the innovation leader in high-frequency EDA. Its software solutions quicken the pace at which high-tech products like cell phones and satellite systems are developed. When AWR software is part of the design process, engineers can deliver cutting edge, affordable products faster, more reliably, and at a lower cost. Headquartered in El Segundo, CA, AWR is a privately-held, growing company with thousands of users world-wide. Learn more: