The spectrum for broadband wireless services in the 60- to 90-GHz bands is challenging designers to develop low-cost CMOS devices that operate in the microwave region. But the path from device to system is fraught with obstacles. Just ask anyone who has ever tried to design a fully integrated low-power multiple-antenna wireless-LAN radio front end at 60 GHz with conventional silicon technology.
Today, conventional transceivers consist of an RF front end, an analog core and a digital signal-processing unit, and make use of many off-chip front-end components (filters, switches, networks, antenna). A 60-GHz transceiver system that has integrated passive components as well as arrays of antennas directly in the package is a vision for the future.
This In Focus report concentrates on the elements that make a front-end system design and takes a look at the challenges for each of them. Two articles by graduate students at the Berkeley Wireless Research Center highlight the latest research. The papers will be presented at the upcoming Communications Design Conference. Another 60-GHz technology paper in the same CDC session details a 60-GHz RF system-on-chip that supports a smart array. The array was designed at National Taiwan University.
Proof of the rapid approach of 60-GHz transceivers can be found in an article by a group from Xignal Technologies AG. The team describes a 10-Gbit/second CMOS transceiver design, which is already available on the market, that exhibits a transmitted clock jitter of less than 200 femtoseconds and no measurable crosstalk between receive and transmit path. Xignal claims to set a new world record in jitter performance for high-speed CMOS designs.
Complementing the research activities are articles that address other elements of high-speed front-end design. Analog Devices Inc. talks about A/D converters in need of stable clocks; Adiabatic Logic Ltd. addresses adiabatic circuits that minimize power consumption in high-speed front ends; and Agilent Technologies Deutschland GmbH takes an optical approach to analog front-end design.