Category Archives: EMC Measurements

Unusual EMC Antennas

Is there anyone who has tried using unusual antennas for EMC troubleshooting or measurement? I’ve recently posted several ideas – some of which I’m actually using for troubleshooting.

Terk_LP_Antenna-102-600-150

Using a DTV antenna: http://www.tmworld.com/electronics-blogs/the-emc-blog/4403939/Using-a-DTV-antenna-for-EMC-troubleshooting

Using a PC board LP antenna: http://www.tmworld.com/electronics-blogs/the-emc-blog/4403451/PC-board-log-periodic-antennas

A simple DIY dipole antenna (Part 1): http://www.tmworld.com/electronics-blogs/the-emc-blog/4398406/Playing-with-antennas—part-1

A simple DIY dipole antenna (Part 2): http://www.tmworld.com/electronics-blogs/the-emc-blog/4401568/Playing-with-antennas—part-2

An EMC troubleshooting kit (Part 1a): http://www.tmworld.com/electronics-blogs/emc-emi-rfi-esd/4378152/An-EMC-Troubleshooting-Kit–Part-1a-Emissions-

Characterizing a Simple Dipole Antenna

As EMC engineers, we use many types of antennas – many broadband, these days. As a traveling EMC troubleshooter/consultant, I reply on small collapsible DIY antennas for troubleshooting, as described in an earlier blog posting.

In order to characterize these adjustable antennas versus frequency, it’s useful to be able to measure them with different element lengths extended, so that you know about where to set the length for the specific harmonics of interest. Using the new Rigol DSA815TG spectrum analyzer with tracking generator, and VSWR (voltage standing wave ratio) option, you can determine both the resonant frequency and VSWR, or how well the antenna is matched to the 50-Ohm coax cable. more…

New Low-NF Broad Band Preamp from Mini-Circuits

One of my favorite companies, Mini-Circuits, developed a (really!) low-noise, broad band, preamp (model PSA4-5043+) earlier this year for use as a front-end amplifier for mobile telecom applications, such as GSM, CDMA, LTE and WiMax. However, it would also be ideal to amplify spectrum analyzers and the low-noise feature would lower the effective noise figure of the analyzer, allowing you to see low-level signals better. This would not only be useful for amplifying near-field or current probe outputs, but would work well to boost the antenna output in semi-anechoic chambers – especially if there is a long run of coax cable.

Lets take a closer look and sweep the gain on our spectrum analyzer. more…

Review: The ARRL RFI Book (3rd Edition)

In my never-ending quest to search out useful reference books on EMC, I recently ran into the 3rd edition of “The ARRL EMC Book” (ISBN 9780872590915). First published in 1999, the new 3rd edition was released in 2010. For those unfamiliar with the ARRL (Amateur Radio Relay League), this is the national organization representing amateur radio operators (“hams”) in the U.S. Most hams are members of the league, which also publishes a range of useful operating, design and general radio reference books. Because hams are allowed to operate their two-way radios at up to 1.5kW, on occasion, this may be the cause of local interference to poorly-designed or poorly-shielded consumer products. Thus, several years ago it was decided to publish a reference book on RFI (radio frequency interference). In this article, I’ll describe the most important content and why you might want to buy it. More…

Using MathCad to Simulate a Square Wave

There are a number of engineering tools that work well for simulating EMC scenarios. One of these is MathCad, a tool that’s been around for a number of years. The neat thing about MathCad is that you can define a set of equations in free-form layout and plot out the analysis in several engineering-type graphs, including logarithmic and polar. These plots are easily copied and may be pasted into documents or technical papers.

As an example, I’ve calculated the harmonic content of a square wave given user-defined fundamental frequency, rise times, pulse widths and duty cycles. It’s very instructive to run through several scenarios prior to building hardware. By changing any of the user-defined parameters, you can quickly judge the outcome. More…

Using A Tracking Generator

Many spectrum analyzers include tracking generators, but some new engineers my not completely understand what the purpose is and how they can help with certain measurements. In a nutshell, tracking generators are variable, or swept, RF generators that “track” with the spectrum analyzer sweep frequency. Some tracking generators have a limited frequency sweep as compared with their mating spectrum analyzer, so you need to know any frequency limitations in advance. In this article, I’ll use the new Rigol DSA815TG and the built-in tracking generator to measure a 150 MHz bandpass filter and a 10 dB attenuator. More…