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Another advantage of millimeter-wave devices is the relative size of the antennas and the device components. These compact components can be very light and portable, which opens doors to more environments in which millimeter-wave devices could be used. On the other hand, the wavelength dimensions of these signals require very precise tolerances on small components (Fig. 4). According to Mark Faulkner, Microsemi’s vice president of RF integrated solutions engineering, “There are tiny features in a waveguide end launch. I have designed and built these things up to Q band. The elements and machined parts look like a grain of pepper, they are so tiny. Imagine gold plating that and screwing it down or attaching it somehow. It is a challenge.”

Millimeter-Wave Technology Prepares For A Wealth Of Applications, Fig. 4

The skin effect causes these higher-frequency waves to travel at the surface of the conductors, making surface finish and plating serious concerns. Small imprecisions in machining also lead to very low yields and higher costs. A solution to these problems has been to develop semiconductor-based millimeter-wave systems and other micro-fabrication techniques.

Another growing trend has been to implement on-chip antennas with self-testing electronics to cut down on expensive millimeter-wave test. Companies like IBM and United Monolithic Semiconductors have implemented processes with tool support for enabling millimeter-wave design as well as digital integration. Testing systems like digital-signal processing, internal noise sources, and loop-back sensing methods can all enable a self-testing device. IBM’s 9HP process uses silicon-germanium (SiGe) BiCMOS for this integration. Other semiconductors used for millimeter-wave electronics are implemented in gallium arsenide (GaAs), indium phosphide (InP), and gallium nitride (GaN).

When working with semiconductor components, difficulties often arise when interfacing to the external electronics or antenna. To manage some of these challenges, companies like Nuvotronics have developed highly refined micro-fabrication methods to create complete millimeter-wave structures in a monolithic process. Nuvotronics claims that its PolyStrata manufacturing technology can be used to make 3D transmission lines with advanced routing while enabling other features with 3D stacking. In addition to being able to create an effective millimeter-wave interface, millimeter-wave surface-mount-technology (SMT) components and other monolithic microwave integrated circuits (MMICs) can be included in the 3D design.

With these advanced fabrication techniques, millimeter-wave devices could soon be found in many commercial and industry environments. With the potential for integrated, ultra-high-speed data connections and low transmission power, this technology also could enable the Internet of Things and Big Data revolutions. At this point, the major factor limiting the adoption of millimeter-wave systems is the cost. “That is one of the fun challenges for me,” Faulkner says, “getting the cost out of these components. If you get the costs low enough, you can enable a market and open up a larger use for these devices.”

Millimeter Waves Enhance Security

Other benefits of millimeter-wave technology include extremely low energy levels of radiation and the ability to generate high-resolution images. These stand-off imagers can also be implemented as passive radiometers, as our bodies naturally radiate millimeter waves. “Passive radiometers take advantage of thermal radiation,” Faulkner explains. “They are completely harmless. Just by the virtue of you having temperature, you are emitting radiation. These passive sensors can take advantage of that.” These devices can be packaged in a small and energy-efficient package deployable in a handheld scanner, such as Microsemi’s Allclear Handheld scanner. Such imagers can be employed in security screening scenarios that quickly and safely inspect individuals and their possessions. Unlike many other security screening technologies, millimeter-wave imagers can be designed into portable platforms and used as standoff imagers.

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