James C. Rautio

Dr. James C. Rautio is founder of Sonnet Software, recognized James Clerk Maxwell historian, and frequent RF Globalnet contributor. His guest columns reflect upon his vast knowledge and industry experience in the fields of microwave circuitry and electromagnetic software development.


  • EM De-Embedding Magic – Part 4: Internal Ports

    To get useful results during EM analysis, answers must be accurate. Errors in impedances of even a few tenths of an Ohm will be disastrous. Those who use an EM port calibration that is dependent on the traditional definitions of Z0 will have that magnitude of error before they even start. In the final article of his four-part series, James Rautio of Sonnet Software addresses the problems that arise during EM port calibration and discusses a powerful technique for tuning filters in just a few minutes with nearly full EM accuracy.

  • EM De-Embedding Magic – Part 3: What Could Possibly Go Wrong?

    In Part 1, I described the EM analysis port calibration algorithm that I developed almost 30 years ago and has been in use in Sonnet ever since. At first glance, it might seem like the technique can be applied only to “lonely” ports — ports that have no interaction or coupling with any other nearby ports. In Part 2, I showed how the algorithm can be easily extended to calibrate and de-embed as many tightly coupled ports as needed. Yes, a couple equations are needed, but once you get familiar with them, the process is really easy to do. Everything works so well, one might think that nothing could possibly go wrong.

  • EM De-Embedding Magic – Part 2: Lots Of Ports, All Talking To Each Other!

    In Part I, I described how I came up with the EM port calibration theory that we have been using very successfully for nearly 30 years. It is so simple. To de-embed a single, lonely port, just EM analyze a 2-port through line of length L, and a second one of length 2L, do some magic math (described in Part I and in [1] and [2]), and we have beautiful, fully de-embedded EM analysis data for that lonely port. (If we have additional lonely ports, just repeat the process for those ports, one at a time, as well.)

  • EM De-Embedding Magic – Part I: What's the Problem, Anyway?

    Way, way back in 1986, when I was developing the Method of Moments software that we are selling today [1], [2], I encountered (and overcame) many problems. One problem first became apparent when I was demonstrating prototype software at HP (now Agilent, soon to be Keysight Technologies) in Santa Rosa, one of my research sponsors. The results did not look so good. When we compared the results to measurement, the differences steadily increased as we went up in frequency. My funding from HP could be in jeopardy. Not good.

  • Patterned Ground Shields For Silicon RFICs – Part 4: How Does the Ground Shield Work?

    You might have noticed, in spite of the title of this series, we have discussed the current induced in the RFIC silicon ground rather than the patterned ground shield that designers add to reduce the current in silicon. As I mentioned in Part 1, we must understand our enemy before we can deal with our enemy. We now understand our enemy.

  • Patterned Ground Shields For Silicon RFICs – Part 3: Which Way Does The Current Really Go?

    Everything is so confusing. In Part I of this series, we found that there is something really strange about the current flowing in an Si substrate underneath a spiral inductor. It is flowing perpendicular to the direction of the spiral turns, when we thought it should be flowing parallel to the turns.

  • Patterned Ground Shields For Silicon RFICs – Part 2: What Universe Are We In?

    In Part 1, we used Sonnet® to investigate the current in the surface of the silicon substrate that is induced by a spiral inductor. Since it is an inductor, we were expecting the substrate current to be induced magnetically. After all, inductors are just little magnets, and we would expect inductively induced current in any nearby conductor. The silicon substrate is a conductor, kind of, right? In addition, the magnetically induced current should flow parallel to (and in the opposite direction of) the current in the spiral inductor. This behavior obeys a special case of Clerk Maxwell’s equations known as Lenz’s Law. This is all, to use American slang, a “slam-dunk”1, hardly even worth checking.

  • Patterned Ground Shields For Silicon RFICs – Part 1: What Happens In The Silicon?

    Spiral inductors and silicon … from an RF point of view it seems silly. After all, we have all that lossy silicon just microns away from our loss-sensitive inductor. We need low loss or our VCO won’t start, or our LNA will have a high noise figure. Put that inductor anywhere but on the silicon!

  • How To Get Your Paper Published At IMS – Part III

    Last time, I went over how to make life easy for the IMS reviewer so that we can increase the chances of getting a paper accepted. It is important to devote conscious effort to making it easy for the reviewer to give high scores in the originality, clarity, quantitative, and interest categories. In this column, I concentrate on the part that I feel is most important, quantitative. Note that all four parts are formally assigned equal weights when assigning scores and other reviewers might have different opinions, so this represents only my personal views on the matter.


  • How To Get Your Paper Published At IMS – Part II

    Last time, we talked about the rationale behind the IMS double-blind review system, where not only are the reviewers not known to the authors, but the authors are not (nominally) known to the reviewers. This reduces the chance of any bias on the part of the reviewer for or against any particular author. However, it also makes it harder for the reviewer to catch double publication. Now, we look at what you can do to increase chances of acceptance.

  • How To Get Your Paper Published At IMS — Part I

    “It’s just an Old Boy’s Club,” my host firmly told me. We were talking about getting papers accepted to the IMS (International Microwave Symposium). After several rejections, he no longer submitted papers to IMS. This is a real shame because IMS is the premier RF/microwave conference in the world. His perception was that the IMS TPRC (Technical Paper Review Committee), consisting of more than 250 of the world’s leading RF/microwave researchers, gave favored status to its own members.

  • The IMS MTT 60th Anniversary Logo — The Back Story

    When I was a boy growing up on a remote farm in the 1960s in the southern tier of New York state, the winters were cold, the nights were long, and the snow was deep. Beyond the necessities of life, we had no spare cash, but I traveled the world anyway. Sometimes, it was by means of a hobby I picked up from my father, ham radio, using “homebrew” radios.

  • The Fellowship

    I presented the student paper awards at the IEEE Radio and Wireless Symposium, January 16 to 19, 2011, in Phoenix, AZ. In each of four areas, I handed out a full university copy of Sonnet, plus personal copies of Sonnet to all of the first- and second-place paper authors. It was a lot of software to a lot of bright young engineers. I felt it was important to do ... because of the fellowship.

  • Metal Roughness Is Weird

    In 2008, I started working with Dr. Allen F. Horn, III, Associate Research Fellow of Rogers Corporation, on metal surface roughness. He was obtaining incredibly weird measurements. He was measuring substrate dielectric constants by means of various microstrip and stripline transmission lines using various substrate thicknesses and various metal foil roughnesses. The substrate material in all cases was LCP (liquid crystal polymer).

  • One Dielectric Constant Is Not Enough

    Electromagnetic analysis should converge to the exact answer as the mesh is made finer. But so many times it does not quite make it. Why? One reason is that using a single value for the dielectric constant — that of an “isotropic” dielectric — is wrong. Two numbers work better.

  • So Just How Much Faster Are Computers Today?

    I purchased my first computer, an Apple ][+, in 1983. I paid US$2,000 for it. At the time, it was a high-end PC (the term personal computer was just then coming into use) with two 5.25” floppy drives, a 6502 microprocessor, and 48 kBytes of RAM. There was no hard drive.