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 1970's and 1980's, 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 1980's and 1990's 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, this once-novel semiconductor 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 (at that time) if it didn't offer higher gains at higher frequencies than silicon bipolars? It is very unlikely. High-frequency engineers are practical, and they will adopt a new technology is it can solve a problem that hasn't been solved before, or can achieve desired performance goals in a simpler manner than before. Cost is not usually a barrier to the initial acceptance of a new technology, unless that cost is so many orders of magnitude higher than existing solutions that it would render the use of the new technology absurd. In general, the cost of a new technology is its highest during early development stages, dropping rapidly as production (and volume) increases.
A Special Report in this month's issue of Microwaves & RF magazine highlights 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, also available on the Microwaves & RF web site (see below) 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) become widespread in the high-frequency industry. 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.
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