Measurement Conference Tackles Differential Testing

The winter biannual meeting of this prestigious measurement society took on the challenge of making measurements on differential devices with single-ended gear.

Accuracy measurements require both science and skill. Knowledge of measurement equipment helps in testing, but often years of experience are needed to hone reliable measurement techniques. Fortunately, a dedicated group in the US, the Automatic RF Techniques Group (ARFTG), gathers twice each year to discuss measurement practices and techniques, and to share the wisdom of their members' experiences. The most recent meeting of ARFTG took place in the Hotel Boulderado in Boulder, CO, December 2-5 2003, with a focus on differential measurements.

The four-day ARFTG meeting consisted of a two-day short course on microwave measurements and instrumentation and the formal conference on differential measurements. The short course, as might be expected for a measurement meeting held in Boulder, was dominated by speakers from the nearby National Institute for Standards and Technology (NIST). NIST speakers included John Juroshek (on RF connectors and transmission lines), Tom Crowley (on microwave power measurements), Dylan Williams (on achieving accurate on-wafer measurements), Tracy Clement (on practical oscilloscope measurements), Paul Hale (with an introduction to optoelectronic measurements), and Jim Randa (on thermal noise measurements).

The NIST reunion was joined by long-time ARFTG member Doug Rytting of Agilent Technologies (Santa Rosa, CA) who spoke on vector-network-analyzer (VNA) error models and calibration methods, Nick Ridler of the National Physics Laboratory (Malverne, England) who discussed uncertainty analysis, Ed Godshalk of Maxim Integrated Products (Beaverton, OR) who covered phase-noise measurements, Jan Verspecht of Jan Verspecht bvba who reviewed on large-signal network analysis, and Howard Reader of the University of Stellenbosch who detailed how to pay attention to electromagnetic compatibility (EMC) in the measurement laboratory.

The differential measurements conference, held during December 4-5, 2003, was chaired by NIST's Dylan Williams who was assisted by NIST's Kate Remley. The conference included sessions on differential measurements, temporal measurements for 40-Gb/s optical-communications systems, nonlinear measurements, circuit and device modeling, and VNA calibrations. In the differential measurement sessions, for example, James Broomall and associates from W.L. Gore & Associates (Elkton, MD) offered practical information on a coaxial-to-differential adaptor capable of making the transition from single-ended 3.5-mm coaxial devices to differential devices. In the same session, Yves Rolain and colleagues from Vrije Universiteit Brussel (Pleinlaan, Brussels, Belgium) explained how to measure the nonlinear characteristics of differential RF amplifiers using a single-ended source. Also, Kipp Schoen of Picosecond Pulse Labs (Boulder, CO) reported on a sub-10-ps differential pulse source for time-domain-reflectometer (TDR) and time-domain-transmission (TDT) measurements.

The next (63rd) meeting of ARFTG, which is dedicated to "on-wafer characterization," is scheduled for June 11, 2004 in Fort Worth, TX in conjunction with the IEEE Microwave Theory & Techniques Symposium (MTT-S). For more information on ARFTG itself or on attending the 63rd meeting, visit the website at

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