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Using Calibration to Optimize Performance in Crucial Measurements
Welcome to March, another special month in our 50-year celebration of Microwave Journal and the microwave industry. This is the month we publish our annual Test & Measurement/CAD issue along with our Cables and Connectors supplement. As in previous years, we dedicate this month to measurement and simulation, two engineering tools that guide us in our quest to understand how technology works and how to advance it. Undoubtedly, studying device behavior is a critical step in developing the next generation of design and therefore deserves our attention.
Keeping with our anniversary year theme, this “special” issue of Microwave Journal includes side-by-side articles on the state-of-the-art in measurements today and a classic from our earlier days. Our reprint article captures both the measurement and device technology of 50 years ago. The extent of the industry’s progress is clearly evident by this comparison of past and present. If your career spans back that far, I think you’ll enjoy this nostalgic journey. If your career is less long in the tooth, you should be amused at how devices were measured back then and appreciate today’s tools even more.
Looking back at my own start in the industry, I remember the VSWR meter and its peripherals as a dusty collection of equipment piled up in the test lab’s supply graveyard, mothballed unless you were among the unfortunate without a replacement budget for aging instruments. In the mid-1980s, fresh out of school, I witnessed a great deal of engineering attention focused on gallium arsenide and MMIC development. As a relatively new piece of test equipment, the automatic network analyzer (ANA) was making a big impact on most of the novel device development occurring at that time.
The ANA (now referred to as the VNA) helped us accurately extract S-parameters, impedances, loss (insertion and reflective) and group delay. It truly was breakthrough technology, spawning such test-lab social phenomena as the sign-up sheet, the measurement guru and the calibration kit with precision torque wrench kept under lock and key by the calibration guru (multiple gurus being budget-dependent). Over time, changing job responsibilities meant less and less contact with the VNA, but in microwave engineering, one never gets too far away from S-parameters. So when it is time to commemorate 50 years of measurements in our industry, I could not think of a better candidate for the spotlight than the network analyzer.
The job of an editor for Microwave Journal is an interesting one. While many individuals who work and study in our industry submit content to the Journalunsolicited, editors must often seek out the help of microwave engineers, managers and marketing folks to get the materials we need for special reports. We rely on these people who are closest to their respective technologies to provide us articles or information on what is happening in their areas of expertise (beware the pestering editor with a deadline). For our cover story, various sources on the web and personal experience made the early days of the VNA relatively easy to write. I found the continuing evolution of the VNA since my days in the test lab to be truly remarkable and considerably beyond what I had been aware of. Detailing all the recent advances in VNA measurements would not have been possible without the timely help from the folks at Agilent, Anritsu and Rohde & Schwarz. These people all know their stuff and I am extremely grateful. It is amazing how quickly technology changes and how quickly we come to adapt to these changes and expect more. VNAs today have much greater capability than just a couple of years ago. They are extremely fast (for acquisition of large data sets), have greater dynamic range, address differential circuit topologies and pulsed operations while providing calibrated measurements far beyond just S-parameters. If you haven’t been keeping up with these advances, now is a great time to read up.
This brings me to a final thought concerning information. In engineering, it is vital that we stay up-to-date, which necessitates information sharing. While protecting intellectual property is vital, technical advances happen faster when we are informed and our achievements are allowed to leap frog one another. Working on something novel and you have some interesting results? Tell the industry and validate your findings while educating potential customers. Looking to find or share information? Attend our online webinars and the invaluable Q&A sessions afterwards, reply to our monthly online Expert Advice column, or send us an article.
We enjoy hearing from our readers and would like to share what you are working on with the rest of the industry. Recently retired Microwave Journal editor Harlan Howe addressed this need in a very popular editorial from several years back entitled “Publish or Perish.” If it’s been awhile since you’ve openly discussed your technical accomplishments, now may be the time to get the word out. To paraphrase Harlan’s message, “Publish and Prosper.” Here’s to your success.
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