Sorry about getting a little behind in postings. Here are some of the highlights of postings on the EDN.com site:
Review: inexpensive RF generator – During one of my presentations on low-cost EMC troubleshooting tools at the IEEE EMC Symposium last August, one of the attendees, Doug Miller, mentioned a small PC-controllable RF generator for just $190. Of course, I had to buy one and try it out!
Review: Windfreak Technologies SynthNV RF generator – Every once in a while, I discover a product that is so incredible I wonder why it hasn’t been publicized more widely. This is the case with Windfreak Technologies $599 miniature RF generator, the model “SynthNV” (Figure 1). In case you’re wondering, their company is named after the owner’s sailboat!
Detecting ESD Events – In my experience, electrostatic discharge (ESD) issues have now become the second-most prevalent issue other than radiated emissions. If you find your product has exhibits random upsets, such as loss of data or unusual circuit resets, it could very well be caused by ESD. This article describes several methods to detect these events.
Harmonic Analyzer Tool – Because of their typically fast edge rates, crystal oscillators can generate a large number of high-order harmonics. This harmonic analyzer was created by my coauthor, Patrick André, with additional formatting tweaks by myself. I find this really handy to calculate harmonics from clock oscillators.
Review: TTi PSA2702T handheld spectrum analyzer – One thing that I find handy is a small hand held spectrum analyzer for use in troubleshooting EMI issues. As I travel a lot in my job, I like to take the minimum amount of test equipment possible. Unfortunately, most good quality analyzers are large, heavy and expensive. About ten years ago, I ran into the Thurlby Thandar Instruments (TTi) PSA2701T and have used it extensively since then. During that time, I reviewed it several times. In May 2013, TTi completely redesigned and repackaged this analyzer and released it as the PSA2702T. This is a review of the new PSA2702T, which I have used for several months now.
The WordPress.com prepared a 2013 annual report for my EMC blog.
Here’s an excerpt:
The concert hall at the Sydney Opera House holds 2,700 people. This blog was viewed about 11,000 times in 2013. If it were a concert at Sydney Opera House, it would take about 4 sold-out performances for that many people to see it.
Click here to see the complete report.
Cables or other metal (antenna-like) structures often couple to sources of common-mode currents and end up radiating, causing product failures during compliance testing. During the troubleshooting process, it would be helpful to determine the resonance of these cables or structures to confirm they are the source of certain harmonic signals.
We could certainly measure the length of the cables or metal structures, but often, they are connected to other conductive assemblies, such as circuit boards or brackets. Because of these system inter-relationships, it’s not always easy to predict the resonances within a system, and so there’s always a little uncertainty as to where to start the troubleshooting process. These simple techniques may help quickly identify potential resonances within your system or product.
One of the most common questions I receive as an EMC consultant have to do with PC board design. And, no wonder. As clock and data frequencies increase towards 10 GHz, proper PC board design becomes an imperative for proper functioning of the system. The typical “rules of thumb” we used for low frequency boards no longer seem to apply.
So, when I ran across Lee Ritchey’s self-published book, Right The First Time – A Practical Handbook on High Speed PCB and System Design (Volume 1), I was intrigued. Both this book and the follow-on volume 2 (Advanced Topics) are available on his web site. Volume 1 is now out of print, but available separately as a 295 page PDF file for just $25. However, both volumes may be purchased for the special price of $95 (the price of volume 2, alone) – a deal I highly recommend. I’ll be reviewing volume 2 later. More…
How many of you store all your connectors and coaxial adapters in one large box? After years of dealing with the jumble of connectors and adapters and the wasted time in pulling out what I needed, I finally decided to make this part of my “spring cleaning.” After rooting around multiple locations for small stashes of these connectors, I cleared off the workbench and sorted them all by size and type. I also decided to collect and sort all the small coaxial connector-related modules, such as combiners, power splitters, amplifiers, etc., as well as other small everyday electronic sub-assemblies I routinely use for experiments.
Once all the various components were sorted out, I paid a visit to our local Walmart and found these five-drawer units (8-1/2″ x 7-1/4″ x 11-1/8″, model 2075) made by Sterilite, which were just the right size to hold the multitude of connectors, adapters, and modules. The drawer modules are stackable, so I can double the storage pretty easily, if required. Because the drawers are clear, I can see at a glance what I need.
For more on this and other storage ideas, click here…
How many of you have beat down a harmonic at one end of the spectrum, only to have an otherwise low harmonic rise up above the limit at the higher end of the spectrum? This is often termed the “ballon effect”, where squeezing one end of a balloon makes it expand at the other end. This is usually due to board resonances within the PC board itself.
I recently received an interesting observation from fellow EMC consultant, Mike Farnet
, following an experiment he performed on reducing the emissions from a client’s embedded ARM processor board with Ethernet. There were strong 25 MHz harmonics from the PHY circuit, as is usual for these low-cost boards. The original harmonic was peaking strongly at 150 MHz. Here is his discussion:I use a 5407 EMCO GTEM and a Rigol DSA-815 TG+EMC spectrum analyzer. I use LabView to collect the data from my spectrum analyzer.
I am working on a 25 MHz issue on an embedded ARM board with Ethernet. The strongest offending harmonic is at 150 MHz. See Figure 1.
Figure 1 – The harmonic profile before the capacitors were changed.
I was growing tired of waiting to collect 16000 data points for the 3 positions in the GTEM and was contemplating limiting the scan window to the 150 MHz target for faster debugging when the scan in Figure 2 told me “Bad Idea.”
Figure 2 – The harmonic profile after the capacitors were changed.
I recently published a review of the following book in EE Times.
One of the most popular versions of SPICE today is Linear Technology’s LTSpice IV. This free and full-featured SPICE modeling software runs on PCs and includes schematic entry, great graphical plotting, and is very fast. While Linear Technology provides a basic on-line user guide, until now, there really hasn’t been a very comprehensive resource on using the software. Earlier this year, components supplier, Würth Electronik, alleviated this missing reference with their 700+ page book, The LTSPICE IV Simulator – Manual, Methods and Applications by author Gilles Brocard.
The software will run on either PC or Mac. To read more and add your comments, click here…
The book, The LTSPICE IV Simulator, by Würth Electronics.
I recently upgraded my old Radio Shack AM radio, which I used for ESD detection, for the Grundig (Eton) Mini400 AM/FM/SW pocket radio. This $30 (street price) pocket-sized radio (4.25 x 2.75 x .5 inch) seems to have plenty of sensitivity to nearby ESD events. By tuning off-station, you can clearly hear the “clicking” from the ESD from several feet away. Using one of these radios is handy for correlating random product glitches with possible ESD events.
I’m also finding it’s quite useful in locating low frequency switch mode power supply (SMPS) EMI. The shortwave bands are especially sensitive to this noise. For example, the CFL and newer LED lamps each have a SMPS built in to their bases. The multitude of these lamps in homes today can create a cacophony of EMI well above the shortwave spectrum. This is a real issue for amateur radio operators and those who enjoy radio astronomy.
The radio has an analog tuner with digital display. It runs on a pair of AAA cells and seems to have plenty of audio. It also comes with a padded case with belt loop. The only caution I might point out is that the power switch is a momentary button, which could get pressed inadvertently if pressed during shipping or if packed tightly in your troubleshooting kit. The radio does have a “Lock” switch on the side that disables the power button, so that ought to alleviate that issue. You just have to remember to unlock the radio prior to use.
AM: 517 to 1782 kHz (1 kHz steps)
SW1: 5.700 to 10.380 (5 kHz steps)
SW2: 11.600 to 18.450 (5 kHz steps)
FM: 85.8 to 108.7 MHz (0.1 MHz steps)
I bought mine from Radio Shack for $40, but you can find one on Amazon.com for $30. Recommended.
Thanks for all the great questions presented following my recent EMC webinar, sponsored by Rohde & Schwarz and hosted by UBM TechOnline. If you missed the webinar, you may go here to download a copy of the slides and listen to the webinar “on-demand”. As I mentioned in the previous three postings, I’ve grouped them by topic and will be answering them all the best I can. Be advised that for many questions pertaining to EMC, the best answer is, “it depends”, so there may not be one answer for all cases. I’ll try to include my assumptions in the answers. The questions have been edited for clarity.
This posting will address general questions on EMC from my recent webinar that were not answered in previous installments. See more…
The annual IEEE Symposium on Electromagnetic Compatibility (EMC) was held August 5 through 9 at the Denver Convention Center. EMC engineers and EMC-related vendors from all over the world met to present the latest technical information, as well as the latest products and services.
Please go here, for the whole article.