RF/Microwave Test From the Cold War to Bluetooth
Component characterization is a primary use of RF/microwave instrumentation. In line with the magazine’s component reliability theme, this may have been the rationale supporting EE’s earliest RF/microwave advertising. In the January/February 1975 issue, Instruments for Industry advertised the Model CC-103 Crawford TEM Cell with National Bureau of Standards (NBS) calibration. Interestingly, a description of Myron L. Crawford’s TEM cell invention had only just been published November 1974 in the IEEE Transactions on Electromagnetic Compatibility.
Crawford was with NBS in Boulder, CO, for a number of years and contributed papers through the mid-1990s on several topics including reverberation chambers. He developed the TEM cell based on work done as early as 1971, and it was featured in a couple of NBS technical notes before the 1974 IEEE publication.
In the late 1970s, Instruments for Industry alternated RF amplifier ads with one for the Model EFS-2 Static Field Sensor, at the time much more in tune with EE’s readers than RF equipment. Hewlett-Packard (HP) advertised the Model HP4191A RF Impedance Analyzer in the March/April 1980 issue, and a full-page VHF/UHF synthesizer ad from Programmed Test Sources ran in March 1984.
This issue also sported the first cover with an RF/microwave theme and featured the HP3577A Network Analyzer. Continuing EE’s expanded coverage of test equipment, the “Smaller and Smarter Is Better” article addressed several types of instruments including RF/microwave generators, analyzers, and counters. One company spokesman commented that the improved instruments were needed to test “new state-of-the-art communication devices, such as frequency-hopping radios, cellular radios, and new surveillance systems.” Companies mentioned included Racal-Dana, LeCroy, HP, Anritsu, Polarad, MCL, and Wavetek.
For several years, March issues typically featured signal generator coverage. In the 1986 issue, TRW’s Mary Ellen Butler, one of few female technical authors writing then, discussed development of systems-level evaluation electromagnetic tests (SLEET), a method of EMP assessment near the end of the Cold War period. This was one of EE’s earliest articles related to EMI/EMC, a topic that in later years would attract much greater coverage.
The March 1987 issue again featured signal generators and discussed the high spectral purity of Comstron’s Model 742. Comstron was acquired by Aeroflex in November 1989. As in the previous year’s March issue, EMP also was addressed, this time by ads from R&B Enterprises for an EMP generator and IRT for EMP stress testing.
The number of RF/microwave-oriented articles was increasing as typified by the November 1988 article “Car Radio Testing Using Synthesized Signal Generators” from Marconi Instruments. EE attracted advertising from a virtual Who’s Who of test and measurement companies, as evidenced by a 200-page issue in October 1984.
December 1989 saw publication of the definitive “Trends in Microwave Testing” by HP’s John Minck that discussed the far-reaching effects of direct-digital synthesis on both RF/microwave system and instrument design. For many years, as Minck stated, engineers believed that modular architectures such as VXI couldn’t handle microwave instrumentation. It has taken between two and three decades to prove otherwise.
Editorial coverage during the 1990s was a mix of staff-written articles about test-instrument advances and application stories from industry experts. Wireless became such an important part of communications that by 2000 at least four articles were dedicated to it each year. In addition to a range of analyzers and generators, power meters also were featured. Older types of power sensors no longer were compatible with the new digital modulation schemes—the topic of the April 1994 Boonton Electronics story “Measuring the True RMS Average Power of a Complex Signal.”
In 2006, EE published 10 RF/wireless-related articles on topics including Bluetooth, multiport VNAs, wireless mesh network testing, and accurate power measurement. Also in this decade, MIMO became an accepted way to support higher performance in both Wi-Fi and WiMax networks. And, as modulation protocols became faster and more complicated, the need for lower distortion amplification prompted greater interest in nonlinear device behavior. In April 2009, “Boldly Going Beyond S-Parameters” looked into the theory behind X-parameters and S functions, and in April 2010, “All the Cool VNAs Are Nonlinear” discussed the commercial solutions addressing nonlinear device characterization.
Regardless of the ways in which the various communications technologies proliferate in the years to come, EE’s in-depth coverage will continue to examine each incremental improvement.