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Kirt Blattenberger - RF Cafe Webmaster

Copyright: 1996 - 2024
    Kirt Blattenberger,


RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while typing up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

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RF & Microwave Magazine Article Archive - 2021

RF & Microwave Magazine Article Archive 2018 - RF CafeIf you are like me, you spend a lot of time reading articles from technical magazines. Sometimes I read the entire article, but usually I just scan the text for highlights and look at the schematics, block diagrams, and charts / graphs. Often, I want to go back and find an article but cannot recall where I saw it. A Google search will usually eventually reveal a hyperlink to the article, but a lot of times it takes a lot of digging. Since my key interests are not necessarily the same as RF Cafe visitors, an attempt will be made to catalog all of them. If there is a magazine not included here that you would like me to include in the list, please send me an e-mail and I will try to incorporate its articles, too.

Aerospace & Defense | EDN | Electronic Design | High Frequency Electronics | IEEE Spectrum | Microwave Journal | Microwaves & RF | Microwave Product Digest |

Aerospace Defense




The Math Behind the Smith Chart

Math Behind Smight Chart - RF CafeMany of us are familiar with the math behind the Smith chart. Some have written spreadsheets and software for creating Smith charts, if only for the satisfaction of being able to do so. It really is quite simple (complex, actually - get it?) to do, but as with most things a genius mind (i.e., Phillip Smith) was needed to think of doing it in the first place. John Dunn, a very smart guy in his own right, posted a good primer on the subject on the EDN website. If you are new to the Smith chart or just want to do a refresh, then surf on over to read his article, and maybe click on the three related links at the bottom for more info.

Tales from the Cube

Tales from the Cube - RF CafeHere's a trip down Memory (640 kB) Lane for those of us around during the early PC days, using MS−DOS. EDN magazine has been running their column "Tales from the Cube" (a take-off of the equally long ago "Tales from the Crypt" TV show) where readers submit sagas of (usually) troubleshooting experiences. Most often the problem is the result of an intermittent event or of human error (pronounced "stupidity"). This is a case of the latter. If you fondly recall the times when 256-color VGA CRT monitors, 3½" floppy disks, 20 MB hard drives, and an i80287 math coprocessor were to die for, when you were deemed a computer expert if you could write batch files, and half your computer's CPU power was not consumed by antivirus programs (no WWW, just Kermit for local net access), then you might like this "The Mysterious MS-DOS Reboot" anecdote by Robert Yankowitz. Enjoy!

What's the Difference Between EMF and Voltage?

What's the Difference Between EMF and Voltage? - RF CafeWhenever I see John Dunn's name I think of the English poet John Donne, but that's my problem. Mr. Dunn wrote an article for EDN magazine entitled, "What's the Difference Between EMF and Voltage?" He begins: "I once read this very strongly-written essay about the difference between electromotive force (EMF) and voltage. The author seemed like he was on some kind of holy crusade and was intensely determined to set his readers straight on fundamental truths that were NOT to be dismissed by infidels. I read his words, but for all of the vitriol, I didn't understand him at all. Recently, I decided to take a closer look at the issue. EMF is given in units of joules per coulomb. The frame of reference for this definition is for any device that uses a non-electrical source of energy to impart electrical energy to a unit of charge, which if given the chance, will flow somewhere..."

Electronic Design

Pay Attention to Harry Nyquist and Claude Shannon

Pay Attention to Harry Nyquist and Claude Shannon - RF CafeJames Mazzei has a good primer entitled, "A Reminder: Pay Attention to Harry Nyquist and Claude Shannon," on information theory at the Electronic Design website, where he admonishes that, "Many CIOs, CTOs, and architects tend to forget this telecommunications throughput issue." Further, "It's a very easy and normal thing to focus on the principal characteristics of the principal components of a communications system or link, and regard other items and issues as peripheral and not so important. That it has happened a surprising amount with satellite communications links, especially remote mobile ones, is the reason for this missive. Here's a hypothetical situation. You are a soldier. You're deployed in a mountainous area of the Middle East, carrying an older Intelsat satellite terminal for immediate access back to headquarters, and the headquarters has leased a 72-MHz transponder..."

Overcome Stray Magnetic Fields with Active Field Compensation

Overcome Stray Magnetic Fields with Active Field Compensation - RF Cafe"As the EV market grows, so does demand for robust magnetic field sensors within these vehicles. Stray magnetic fields may diminish the accuracy of these sensors, though, which is where active stray-field compensation comes to the rescue." So begins Frederik Berstecher in his article entitled, Overcome Stray Magnetic Fields with Active Stray-Field Compensation, posted on the Electronic Design website. Continuing, "The electric-vehicle market continues on a serious upswing: Allied Market Research forecasts show it will reach $802.81B by 2027, up from $162.34B in 2019 [can they really estimate to 5 significant digits? - KRB]. Such growth also pushes the need for additional magnetic field sensors within these vehicles for position detection. The sensors are robust enough to withstand a variety of harsh environmental conditions, temperatures, vibrations..."

High Frequency Electronics

Eravant (SAGE Millimeter) Microwave Products

Eravant (SAGE Millimeter) Microwave Products - RF CafeIn case you haven't heard yet, SAGE Millimeter, which was formerly SAGE Laboratories (if I recall correctly), is as of year 2020 called Eravant. mm-wave waveguide components are always très-cool in appearance, and there are a bunch of them shown on the High Frequency Electronics website. Seeing them arrayed under special lighting in an exhibit at a trade show reminds you of a jewelry store display case. The precision machining and often polished surfaces make them gleam. Here is a great idea (IHMO) for the marketeers at one of these mm-wave companies: Create a children's play set a la LEGOs consisting of plug-together waveguide components molded to look like common parts. Many of them could be full-size if modeled after higher frequency lines. Rigid and flexible, rectangular and round waveguide, antennas, towers, couplers and amplifiers, circulators, rat races, and many other shapes in bright colors would make for some awesome-looking projects and just might produce some of the world's next RF / microwave / millimeterwave engineer. Maybe call them WEGO (WavEGuideO). Or, create a breakfast cereal using those shapes and call them Engineerios (Cheerios). You're welcome.

Understanding Stability Circles

Understanding Stability Circles - RF CafeIt has been a while since I saw an article discussing stability circles for amplifier design. Ain Rehman has one posted on the High Frequency Electronics website entitled, "Understanding Stability Circles." Even in the age of computer design and optimization for just about everything, it always help to have a basic understanding of what the result should look like as well as what affects the result. He begins: "Stability circles are a tool, used to examine and analyze the stability of an amplifier (in the case under discussion) using a graphical technique, with the help of a Smith Chart. (Note: A free, demo version of smith chart software is available on the web from Fritz Dellsperger). This monograph presents the stability circle tool for engineers. It is understood that many CAD programs can generate these, but it is always useful to understand the stability circle on an intuitive level as a good engineering practice..."

IEEE Spectrum



Microwaves & RF



Microwave Product Digest



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