Viewpoint: Understanding Specsmanship

Aug. 6, 2004
Power dividers/combiners are considered "essential" components by most amplifier designers. Now available at RF and microwave frequencies in a wide range of packages from roughly 100 suppliers (not to mention distributors), these versatile ...

Power dividers/combiners are considered "essential" components by most amplifier designers. Now available at RF and microwave frequencies in a wide range of packages from roughly 100 suppliers (not to mention distributors), these versatile components allow the combining of multiple power transistors in a high-power-amplifier (HPA), for example, or the splitting of signals two, four, or almost as many ways as desired. A Special Report beginning on page 33 details some of the things to look for when selecting a power combiner/divider.

In the midst of poring over hundreds of data sheets of research on power dividers (tirelessly collected and captured from websites by Editorial Assistant Dawn Prior), it became apparent that specifications are not always what they seem. The two obvious examples of this are two of the power divider/combiner "quality" specifications: amplitude unbalance (or balance or tracking) and phase unbalance. While almost every manufacturer standardizes the way they present their own data, comparing data between different manufacturers can sometimes be a challenge. For these two specifications, for instance, many manufacturers choose to present their performance levels in terms of a deviation, such as plus minus0.3 dB for amplitude unbalance and plus or minus 6 deg. for phase unbalance. But just as many manufacturers present these same two specifications as the total range of unbalance, namely, 0.6 dB for amplitude unbalance and 12 deg. for phase unbalance. And in some unfortunate cases, suppliers list what appears like it should have been a deviation, such as plus or minus 0.5 dB for amplitude unbalance, as simply 0.5 dB.

Some manufacturers are to be applauded for their efforts to provide as much data (for a comparison) as possible. Mini-Circuits (Brooklyn, NY), for example, is one of the few power divider/combiner suppliers that include a set of S-parameter data for their components. This data shows values that are considerably higher (certainly not an advantage) than those of competitors, because the data also include division losses (along with the expected insertion loss). While making their products appear to have worse performance (if not properly compared) than a competitor, these data are useful to designers who must consider all losses in a microwave link budget, for example.

Until the industry agrees on a standard format to present data, power divider/combiner specifications (including CW and peak power) must be interpreted before they can be meaningfully compared. But while there is room for interpretation, there is room for specsmanship and unfair comparisons.

Please share your thoughts with our readers via the MWRF Forum (see below). Or you can contact me directly at: [email protected]

Reference Links:

MWRF --> http://lists.planetee.com/cgi-bin3/DM/y/eA0JtlqC0Gth0BKHX0AM

Mini-Circuits --> http://lists.planetee.com/cgi-bin3/DM/y/eA0JtlqC0Gth0BF4d0A8

About the Author

Jack Browne | Technical Contributor

Jack Browne, Technical Contributor, has worked in technical publishing for over 30 years. He managed the content and production of three technical journals while at the American Institute of Physics, including Medical Physics and the Journal of Vacuum Science & Technology. He has been a Publisher and Editor for Penton Media, started the firm’s Wireless Symposium & Exhibition trade show in 1993, and currently serves as Technical Contributor for that company's Microwaves & RF magazine. Browne, who holds a BS in Mathematics from City College of New York and BA degrees in English and Philosophy from Fordham University, is a member of the IEEE.

Sponsored Recommendations

Forging the Future of Defense

Oct. 11, 2024
Raytheon’s Advanced Technology team incubates capabilities that fuel the future of defense. Together with leading research and development organizations, def...

Phase-Matched Cable Assemblies

Oct. 8, 2024
Phase-matched cable assemblies are ubiquitous, and growing in popularity. Electrical length matching requirements continue to tighten and the mechanical precision of cable construction...

3 New Wideband MMIC LNAs Cover 5.5 to 20 GHz

Oct. 8, 2024
Mini-Circuits’ expanded PMA3-series of wideband, ultra-low NF MMIC amplifiers operates in ranges between 5.5 and 20 GHz.

Wideband Amplifiers Variable and Temperature-Compensated Gain

Oct. 8, 2024
Many types of RF systems and applications that span from the upper end of microwave frequencies to the lower end of mmWave have arisen in recent years. Meeting system requirements...