Getting More out of VNAs with Greg Bonaguide

Greg Bonaguide, one of the authors of VNA Applications Handbook, that published in September from Artech House, discusses what influenced the writing of his book…

Four observations that influenced my writing of the “VNA Applications Handbook”

A number of factors converged to make the “VNA Applications Handbook” a reality.  Having had the opportunity to work with many development and test groups over the years, I felt the timing was right to give back to the community that had challenged and grown me.  Plus, the influence of the following four factors confirmed that there was a real need for an applications-centered VNA resource:

  1. Pressure to deliver.

How many times have you heard “I need it yesterday”?  Today, companies are driven to be first to market with considerable financial consequences if they fail to deliver.  This pressure trickles down to engineers and technicians who must accomplish more stuff with fewer resources (training, time, and/or technical assistance).  The net outcome ranges from inefficient use of expensive resources to costly mistakes, with plenty of stress in-between.

  1. Lack of application-focused information.

“Read the manual!” said no-one. Ever!  (At least no one who had to use test equipment to make meaningful measurements.)  The basic VNA User Manual clocks in at over 1000 pages and explains each button and menu in minute detail, but often fails to provide the critical action sequences for particular user applications.  Of course there are “app-notes,” but these may run 50-70 pages and often sidestep the “gotchas” that lurk just beyond the edge of the page.

  1. Common customer inquiries.

In day-to-day conversations with customers, common themes emerge.  Regardless of the VNA application, many “newbies” make the same mistakes, whether screwing on a connector (“turn the nut, not the body!”), or performing a calibration (in older cal kits, the ‘Thru’ cal standard length is improperly defined for uninsertable connectors, resulting in phase measurement errors).  Even experienced users must confront unique application pain points:  For filters, it’s the trade-off between sweep speed and dynamic range in the critical transition- and stop-band regions.  For amplifiers, it’s making sure the VNA receivers maintain acceptable signal-to-noise ratio (SNR) at low power levels while simultaneously avoiding compression at high power levels.

  1. Information that doesn’t show up on a datasheet.

Datasheets are notorious for telling only part of the story.  Two competing instruments claim to make the same measurement, but how easy are each to configure?  In addition, there are technology-driven differentiators, like new synthesizer architectures for VNA sources and receiver LOs that have revolutionized (and greatly simplified) frequency converting measurements, and high-power GaN devices that are busting traditional dynamic range boundaries.  Which begs the question: how does your 20-year-old box stack up against today’s VNAs?

In short, I wrote the VNA Applications Handbook to be a “one-stop shopping guide” to help engineers and technicians, regardless of expertise level, get more out of their VNAs.  Quickly.  By design, the VNA Applications Handbook is not an exhaustive compendium of electromagnetic wave theory (and other mathematics) as applied to VNAs.  Instead, it is designed to be a dynamic application assistant, focusing on the measurements you need today while avoiding the costly mistakes you’d otherwise come to regret tomorrow.



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