Tatsuo Itoh, Linda Katehi
Hardware provides the building blocks for the specified requirements and functions of wireless communication systems. In many defense and satellite systems, devices and circuit designs are aimed at the best performance, although the choice of hardware is often conservative. In the case of wireless communication systems, this conservative approach is somewhat true because of the rapid turnaround in commercial products. In fact, manufacturability and marketability become the drivers for many high volume short-cycle commercial products as many industrial participants in this study like Dr. J. Golio of Rockwell emphasized. However, in looking at the future beyond the G3 and even G4 environment, research concerning hardware needs to be advanced in a steady and accelerated pace. This includes not only devices and circuits, but also enabling process technology and design methodologies. This is because the performance of future wireless systems critically depends on hardware capability. Dr. Golio mentioned that the faster, smaller, lighter and cheaper philosophy still holds. It is also true that research methodologies for hardware may need to be modified.
One of the factors influencing hardware research is the frequency of operation, which affects bandwidth and signal processing speed. Although much industrial effort is aiming at frequencies up to 2.4 GHz (at most 5.7 GHz) for mobile wireless and 28 GHz for fixed wireless such as LMDS, several industrial research centers are looking at much higher frequencies beyond 60 GHz. Although the need for bandwidth far exceeding the G3 requirement is often questioned, research on higher frequency devices and circuits has at least two benefits. One is to enable a potential system that takes advantage of the wider bandwidth such as 5 GHz around a carrier frequency of 60 GHz, as envisioned by Sony for ultra-wideband wireless connections. Another is to make low frequency design more flexible and device and circuit performance superior through the availability of higher frequency devices used lightly.
Since hardware research is motivated by system requirements, listing some of the desired features for the future systems and the potential technologies necessary to achieve these goals is a good place to begin. The list is not intended to be exhaustive, but it includes features envisioned by some industrial participants in the WTEC study. Dr. Walid Ali-Ahmad of Maxim, who is engaged primarily in silicon based wireless systems, provided the following list of targets for future circuits and devices:
Dr. Ali-Ahmad provided the following list of device and circuit technologies needed:
In regard to the device technology, a number of other study participants from the United States and abroad emphasized the importance of III-V devices for high frequency applications such as 5.7 and 60 GHz (Mr. Kawasaki of Sony, Dr. K. Honjo of NEC, Dr. Kagiwada of TRW). In fact, TRW can deliver a 190 GHz amplifier based on III-V technology. On the other hand, many people considered SiGe as a promising device with potential low cost, high frequency applications.