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Doing More With Passive Components

Improvements in passive components often come slow and hard, but they still come. Amazingly, after all these years of living with well-established passive circuit designs, such as Wilkinson power dividers, one might think that there was no longer room for improvements. But most manufacturers of RF/microwave passive components take great pride in their products, even those that have been in the catalog for a number of years, and most relentlessly pursue ways to improve on what has gone before.

Some recent visits to local manufacturers of passive components, notably ARRA, ET Industries, Micronetics, Synergy Microwave, and Werlatone, gave a glimpse into the dedication with which highfrequency design engineers seek new ways to improve upon existing designs. Many passive component designers have a fascination with handling high power levels. Not all are adventurous enough to test their own creations, but would like to know if the latest design can handle more power than the last iteration.

High power was a common topic at these companies. Some gave credit to new blends of circuit-board materials with higher thermal conductivities. Many also mentioned using computer-aided-engineering (CAE) software, such as tools from SolidWorks or COMSOL, to predict the thermal flow through their designs. As many pointed out, such tools are helpful for performing "what if" analyses of designs with different types of junctions or substrate materials or even coaxial connectors. But they are no match for an active imagination, one capable of visualizing the flow of electronics through a passive circuit design.

In recent years, designers of passive components have shown great ingenuity in shrinking devices like hybrid couplers and power combiners/ dividers into the size of resistors. Their efforts have brought high-frequency signal processing to many portable, hand-held products, including cellular telephones. But the designers of larger passive component designs are also to be lauded for how they have found ways to reduce insertion loss, improve return loss, increase isolation, and shrink the size of these components. These are "old school" passive components, available for years. But they are used in a wide array of systems and are vital to those systems. By shaving a tenth of a decibel in insertion loss and adding another 10 W in power-handling capabilities, modern designers are taking those small steps that lead to large improvements in many important systems.

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