Introduction
In the last three months, we have introduced how to manually make the radiated emissions pre-compliance measurements for consumer, automotive, and military products, including all the system gains and losses. Once we complete the calculation for each dominant harmonic, you can directly compare the harmonic amplitude to the appropriate test limit. Unfortunately, this manual method can be time-consuming if there are many harmonics over the limit. That’s where automated pre-compliance software saves the day!
This article will review three examples of free or affordable pre-compliance measurement software, some of which I’ve personally used. Two of the examples require using the manufacturer’s hardware. One is designed to work with several different analyzers.
Objective of the Software
Typically, all the software examples will first sweep and measure the desired band in peak detection mode. Following that first sweep, the software will optionally measure using quasi-peak or average detection. The software will display limit lines according to the EMC standard specified. All are designed to be used on a PC.
Many of the software packages will also display a table of harmonics greater than some default dB from the noise floor and indicate passing or failing and margin from the limit. All packages will print out a full test report with measurement equipment and serial numbers, test operator, measurement facility address, and contact information, along with an emission plot and table of results.
All the software packages require you to input the gain and loss versus frequency data for antenna factor, cable loss, preamp gain, and attenuator loss (if used). This data is usually entered in frequency steps. For example, antenna factor will usually be supplied by the manufacturer in steps of 5 or 10 MHz. The software will interpolate if a harmonic is measured between these frequency steps.
Examples of EMC Pre-Compliance Software
Tektronix EMCVu
The pre-compliance software I’m most familiar with is Tek’s EMCVu. EMCVu is based on Tek’s SignalVu-PC measurement and analysis software and EMCVu is a licensed option. It is useful for both troubleshooting and pre-compliance testing and works with all of the current Tektronix spectrum analyzers. Because I’m on the road or giving live presentations a lot, I typically bring along the Tek RSA306B real-time USB-controlled spectrum analyzer that tunes from 9 kHz to 6 GHz.
The software includes a handy setup guide that steps you through the process of adding measurement system gains and losses, such as antenna factor, preamp gain, and coax losses. Figure 1 shows a composite of antenna factor, preamp gain, and coax cable loss.
The setup guide also has several common FCC, CISPR, and MIL-STD-461 built-in limits, which are selectable. Users may also add custom limits for standards not listed. The guide also prompts users for test location and product information, which will be added to the built-in report generator.
One really handy feature is the fast sweep (2-3 seconds for a 30 to 1000 MHz sweep) in the default peak detection mode. Each emission is measured, ranked, and numbered in order of amplitude and color-coded if it’s over the limit (red) between the limit and the 6-dB margin (orange) and below the 6-dB margin (no color highlight). Figure 2 shows various peaks labeled with numbers and shows the amplitude ranking (default) or by frequency. You can see immediately which harmonics are dominant.
Each peak may then be individually selected, and a quasi-peak measurement may be made and recorded in the table. Peak measurements are denoted with triangles and quasi-peak with squares superimposed on the plot and recorded in separate columns in the peak table. Once your measurements are completed, you can generate a report that includes the test location, test operator, equipment used, the plots, and a table of measurements.
One last feature I’ll describe for pre-compliance testing is the handling of ambient signals. When performing a pre-compliance test outside of a shielded chamber, you’ll tend to pick up both ambient transmissions and product emissions. You first use EMCVu to measure the ambient signals with the product under test off. Then perform a second sweep with the product on and the software will subtract out most of the ambient transmissions, allowing you to focus on the actual product emissions. I say “most” because, with two-way radio communications or for mobile phones, the signals come and go, so the first sweep may not catch everything. It’s still a very useful feature.
There are many more troubleshooting-related measurements that can be performed, but I won’t go into that for the purposes of this article. A software license is required.
Price: $4,100 (node-locked), $5,330 (floating).
Signal Hound
Signal Hound is best known for their line of USB-powered real-time spectrum analyzers and RF generators. I’ve had a chance to use their middle-end analyzer, model BB60D, for a while now, which tunes from 9 kHz to 6 GHz. This is an upgrade from the BB60C and includes a more robust front-end fending off ESD damage, 10 dB better dynamic range, and passive pre-selection filters (from 130 MHz to 6 GHz), which greatly reduce internally-generated spurs.
Signal Hound has also developed a troubleshooting and pre-compliance software called Spike. Spike is free and is constantly being upgraded with new functionality. It has all the usual troubleshooting features but also includes means to enter measurement gains and losses in tabular format. It also includes the ability to load in custom limits and frequency ranges and these can be saved and recalled. It also includes a report generator feature.
Figure 3 shows a typical screen for a CISPR 11 Class A emission plot. The harmonic frequencies and amplitudes are also shown in tabular format below the plot. Detected harmonics are numbered and ordered by frequency (default) or by amplitude and displayed in the plot and in a spur table, which can be downloaded. There is an option to display only the failing harmonics in the table.
There is also a “meter” feature like most of today’s benchtop spectrum analyzers. By selecting a particular harmonic, you can see an immediate measurement of peak, quasi-peak, and average measurements in the three vertical meter bars. The quasi-peak measurement uses a custom digital filter that matches the time constants required by CISPR and ANSI standards.
No software license is required. To download, see Reference 2.
Price: Free (with unlimited updates).
Tekbox EMCview
The Tekbox EMC compliance software EMCview for PCs is primarily designed for pre-compliance testing of radiated and conducted emissions. However, it may also be used for automated testing using the complement of Tekbox LISNs, RF current probes, measurement antennas, and TEM Cells. Built-in gain and loss correction are included for cables, amplifiers, attenuators, LISNs, TEM cells, antennas, RF current probes, filters, and any other component in the signal chain.
All the most common emission-related standards and a few automotive manufacturer standards are preconfigured in corresponding project files. The project files take care of all necessary settings to conduct standard compliant measurements. Custom projects may be developed using the built-in editor or any simple text editor.
Besides a fast peak scan, the graph supports two complete measurement runs such as average plus quasi-peak or peak plus quasi-peak. In addition, a fast quasi-peak scan of critical harmonics may be made. Quasi-peaked emissions will be labeled with an “X” in the plot. Graphs can be saved and overlaid with newer measurements to track and document design modifications. A unique “magnifier” feature is included for those cases where several peaks may be closely grouped together. A report generator feature is included.
A bonus is that immunity testing is supported with dedicated menus, controlling the spectrum analyzer’s tracking generator. This would be valuable in replicating a limited radiated immunity test using a TEM cell or configuring a scalar network analyzer measurement to characterize filters, preamplifiers, and cables.
An enhanced version of the software, EMCview PRO, offers real-time measurement support for spectrum analyzers with real-time capability. Users with a standard EMCview license have the option to upgrade to EMCview PRO. Real-time analysis would be most useful for general troubleshooting broadband EMI or capturing intermittent harmonic spikes.
While Tek’s EMCVu and Signal Hound’s Spike are designed to work only with their own products, EMCview currently supports the following spectrum analyzers:
- Rigol (DSA and RSA)
- Siglent (SSA/SSA plus/SSA -R and SVA)
- R&S (FPC and FPH)
- OWON XSA, HSA and NSA series
- Teledyne Test Tools T3SA series
- BK Precision 2683 series
- Com-Power SPA-900TG series
- Multicomp MP700xyz series
- TheEMCShop ESA and RESA series
- UNI-T UTS series
In every case, the spectrum analyzer should be equipped with the EMI option.
NOTE: While EMCview is a free download, the software is limited to an upper frequency of 10 MHz without a license to try it out. Tekbox offers two license options:
- Analyzer-coupled – the license is coupled to the serial number of the spectrum analyzer. It can be installed on any number of PCs, but it can only control one dedicated spectrum analyzer
- PC-coupled: the license is coupled to the Host ID of the PC. It can control any of the supported spectrum analyzer models, but it can only be installed on one dedicated PC
To download the unlicensed version for tryout (10 MHz upper limit), see Reference 3. For U.S. customers, EMCview may be purchased from Saelig Electronics (Reference 4).
Price: Base version $449, PRO version $699 (with unlimited updates).
Summary
You’ll find using automated software for radiated emissions in-house pre-compliance testing makes both troubleshooting and mitigation so much faster. All three companies reviewed also have much more information and application notes available for download. Be sure to check out the references for more.
While a bit pricy, most of my experience has been with Tek’s EMCVu, and I like the sweep speed, fast labeling and sorting of harmonic peaks, automated ambient cancellation, and report generator. I’ve used this for dozens of client projects. The measurement setup screens are quite helpful, especially for users new to pre-compliance software.
Trying out the latest version with my new Windows 11 PC revealed a couple of minor bugs, and I suspect they’ve been corrected by now. Overall, I thought the control layout was pretty user-friendly with major measurement functions arranged along the top as buttons.
I decided to try out Signal Hound’s Spike software for my presentations last May 2024 in Chicago, Detroit, and England. I really like the small size and performance of their BB60D analyzer. I did note a bug in the peak table of the straight analyzer function in that when measuring in dBµV, the peak table presents the peaks in dBm instead. When using the pre-compliance function, this was not an issue. I also wish the analyzer could be set to a log-frequency scale rather than linear, as this would make troubleshooting quicker. The setup control layout was pretty clean and table functions are arranged down below the table.
Tekbox’s EMCview was a little harder for me to understand at first due in part to the multitude of control functions. There are multiple configuration selections and checkboxes required to set up a measurement from scratch. One thing that greatly helped was the dozens of preconfigured standards and limits I was able to select. They even include some automotive standards. I found that starting out with a pre-defined test setup and then customizing it to your needs was the best option.
Correction data for antenna factor and preamp/cable gains/losses can be imported as text files. A bonus is that there are features for radiated and conducted immunity tests and that the software is preconfigured for using various Tekbox products.
All the software packages required a certain learning curve in that various common setup controls are all in different locations. For example, to use the meter bars in Spike requires you to “turn on” that feature after clicking on a desired harmonic.
All three packages mentioned here are also able to utilize the real-time capture modes for analyzers that have that feature (EMCview requires the PRO version). This is more important for troubleshooting broadband EMI or fast intermittent harmonics. Both EMCVu and Spike will also demodulate several types of digital modulation.
I have not had a chance to review pre-compliance (or compliance) software from Keysight or Rohde & Schwarz, but I’d expect the features would be similar to those mentioned here with similar pricing and licensing to Tek’s EMCVu. If you use one of their excellent analyzers, I’d recommend sticking with their offerings. There are similar software pre-compliance offerings from Siglent and Rigol that I may review in the future.
This wraps up the four-part series on performing in-house radiated emissions pre-compliance testing. I hope you enjoyed learning how easy it is to perform. You should find that confirming pass/fail and local resources to help troubleshoot and mitigate EMI in-house is a huge cost- and time-saving benefit. Next month, I’ll do another design review of an embedded processor board, demonstrating my step-by-step process.
