Emerging technologies impact high-frequency electronic designs by providing alternative approaches to achieving a function. The function may be a simple as amplifying a signal, or a complex as restoring lost bits to a data stream. But what determines the acceptance of a new technology? Why do some seemingly innovative technologies fall by the wayside?

Most engineers learn to evaluate new technologies for their practical merit. Semiconductor technologies offer a good example of this. Although silicon bipolar technology served many solid-state high-frequency applications throughout the 1970s and 1980s, it was the considerable investment by DARPA during the latter decade that fostered advances in gallium arsenide (GaAs). Most major defense contractors, such as Boeing, Raytheon, TRW, and the firms that would become component parts of Lockheed Martin and Northrop Grumman participated in DARPA's MIMIC program with the eventual result that the yields of GaAs wafers improved, noise figures dropped, and gain and output-power levels increased. GaAs was also attractive because it lent itself to integration. The growth of wireless markets in the late 1980s and 1990s brought high-volume commercial outlets for GaAs that encouraged increases in wafer sizes. As device designers expanded the technology from early MESFET designs to other structures, such as high-electron-mobility transistors (HEMTs) and heterojunction bipolar transistors, the technology grew to acceptance levels that have all but eclipsed silicon bipolars in high-frequency circuits.

Would RF and microwave engineers have embraced this relatively new technology if it didn't offer higher gains at higher frequencies than silicon bipolars? It is very unlikely. Engineers are practical, and will adopt a new technology if it solves a problem or helps simplify the attainment of a design goal, even if the cost is higher at first.

A Special Report beginning on p. 33 details some of the more visible emerging technologies currently impacting high-frequency designs, including microelectromechanical systems (MEMS) and ultrawideband (UWB) transmissions. A longer version of the article, available on the Microwaves & RF website at www.mwrf.com, includes additional technologies of interest, such as multilayer fabrication technologies and wide-bandgap semiconductors, such as gallium-nitride (GaN) and silicon-carbide (SiC) devices. Not all emerging technologies, such as high-temperature superconductors (HTS), are adopted. But if the major military contractors take an interest in an emerging technology, as they have with MEMS, UWB, and GaN, it is a good bet that the technology will still be flourishing in 20 years.