We have developed a 120-GHz-band wireless communication link that uses photonic and electronic technologies for the
generation, modulation, and amplification of 125-GHz signals. Photonic technologies are suitable for generating ultra-high
frequency signals, and enable long-distance wired transmission and the distribution of millimeter-wave signals.
All-electronic systems, on the other hand, have the advantages of being compact and inexpensive, especially when the
transceiver functions are implemented with monolithic microwave integrated circuits (MMICs). We succeeded in the
error-free transmission of a 10-Gbit/s data signal over a distance of 450 m, and estimated the maximum transmission
distance to be about 2 km.
Microfabrication technologies for use as practical methods in > 10-micrometers featured high-speed device fabrication have been developed: the thick polyimide-used damascene process, electroless plating of Ru/Ni on Cu interconnections, the area-restricted chemical mechanical planarization to polish thick polyimide films. Applying their technologies to fabricate RF-components and millimeter-wave components on Si demonstrates excellent characteristics: high-quality factor (Q-factor) in spiral inductor, low transmission loss for sidewall coplanar waveguide (CPW), high-power radiation in CPW-fed sot antenna. The Si-technology-based approach to achieve seamless integration of different kinds of devices, i.e., photonic devices, ULSIs, RF-devices, and millimeter- wave devices are promising ways to fabricate high-speed systems on Si.