Passive components are those taken-for-granted building blocks that make sophisticated military and commercial systems work. While they may lack the luster of their active counterparts, they are as essential. And although the advances in semiconductors may be more visible, advances in passive components over the last decade have been no less impressive.

The efforts at miniaturizing established passive components, such as baluns, hybrid couplers, directional couplers, and power dividers, by a long list of industry companies that includes Anaren Microwave, Merrimac Industries, Mini-Circuits, StratEdge, and Synergy Microwave, have yielded incredible shrinking passive components that are approaching the size of surface-mount circuit elements, such as resistors and capacitors. In some cases, such as with Dielectric Laboratories, the company developing the components is also the source of advanced material technology. For Dielectric Laboratories, it is high-quality ceramic substrates (and their capabilities in machining them) that enable the firm to offer microwave and millimeter-wave resonators and filters (see the microwave white paper in this issue).

In most cases, however, the company working on components is relying on an outside source for its advanced materials. And in terms of improvements in passive components, the progress made by materials developers is sometimes lost in the telling of the tale. Of course, there are really two sets of companies here: those manufacturing the raw materials and those providing fabrication services for those materials. Both have played important roles in the advances reported for passive components in this month's Special Report (p. 33). The former group includes such suppliers as Arlon, Brush Ceramic Products, Chomerics, Dupont, Kyocera, Park, Polyflon Co., Rogers, and Taconic. The latter group includes Accumet Engineering, Applied Thin-Film Products, Barry Industries, Filtran, and Modular Components.

Perhaps nowhere in the industry is there the close working relationship than between the companies that supply materials and those that process them. The end result is improved materials, which lead to improved components. Not long ago, many materials suppliers were known for good performance, but at military prices. Pressures from the digital design community for higher-speed processing, and from those involved in wireless applications, have resulted in better materials at lower prices. And with these material improvements have come a generation of passive components that is smaller than once through possible, but still handling considerable power levels. Hats off to those passive-component designers, but appreciation also to the materials suppliers.