NTT Research and Development 2008 Review of Activities

The broadband communication environment has been developing very rapidly. High frequency bands such as the quasimillimeter-wave and millimeter-wave bands have the advantage of getting wide frequency bands and providing broadband communication services. NTT Laboratories have developed a quasi-millimeter-wave fixed wireless access (FWA) system for broadband service that uses optical fibers and wireless equipment. Interconnections between components operating at these frequencies cause connection loss, impedance mismatching, and so on, hence, the use of quasi-millimeter-wave interconnects should be avoided. However, it is difficult for conventional MMICs^*1 to integrate many quasi-millimeter-wave circuits, because such circuits require impedance matching, which makes the chips too large.

NTT Laboratories have also developed three-dimensional-MMIC (3D-MMIC) technology that has multilayer dielectric films and metal lines on an ordinary MMIC. It can trap electromagnetic fields in a small area and miniaturize high frequency circuits. We achieved a extremely high level of integration using this technology, almost all quasi-millimeter-wave circuits of the FWA equipment are integrated in a 3 mm x 3 mm area. We also developed another 3D-MMIC that had a quadrupler and driver amplifiers. The integration degree is 20 times higher than that of a conventional chipset. The 3D-MMICs have a conversion gain of more than 20 dB in the transmitter mode and more than 40 dB in the receiver mode and a noise figure of 3.4 dB. Its power dissipation is only 0.5 W.

This technology makes it possible to miniaturize and decrease cost of quasi-millimeter-wave and millimeter-wave equipment and to deploy broadband services early and inexpensively in areas affected by the digital divide. It also can be used in WPAN^*2 equipment.

• *1 MMIC: Monolithic Microwave Integrated Circuit
• *2 WPAN: Wireless Personal Area Network