CMOS technology dominates the digital domain and for a long time it was considered to be not suitable for the design of RFICs. This was due to factors like, e.g., low Q values for integrated inductors, a limited set of available active and passive devices, the fact that CMOS technology is optimized for digital applications, the missing of accurate device models at GHz frequencies, or a worse gm/I of CMOS transistors compared to bipolar transistors. Advances in CMOS technology, while mainly driven by digital needs pushed the transit frequency of today’s 0.13 μm CMOS transistors beyond 50 GHz. Together with improved device modeling and the growing number of interconnect layers, which allows for the realization of improved passive components, RF CMOS has become increasingly popular in the last few years. With an integral design approach, taking into account aspects from system level down to device physics, even applications in the 5 GHz range and beyond have been realized. Advances with respect to improved devices, circuit topologies, and system level architecture also make RF CMOS a strong contender for W-CDMA applications. The majority of the published RFICs for 3G applications is still fabricated in bipolar or BiCMOS technology. However, 3G CMOS solutions are developed in industry and academia and there is little doubt that in a few years CMOS will have a substantial or even a dominant market share in RF applications.
