ABSTRACT
This chapter describes direct conversion architectures for radio applications and the impact of silicon germanium (SiGe) technology on such architectures. It illustrates various challenges in the development of such architecture from an integration standpoint. The chapter demonstrates the development of two variants of fully monolithic radios in a second-generation silicon germanium bipolar complementary metal oxide semiconductor (BiCMOS) technology. It considers various practical aspects of these radios, with an appreciative viewpoint of both the simplicity as well as the complexity of such developments in a silicon-based environment. The chapter presents the case studies of direct conversion radios for IEEE802.11a standard. The circuits in direct conversion system must also provide a high level of reverse isolation. For the case of a Low-Noise Amplifier (LNA), a cascode topology provides about 30 dB reverse isolation, which is quite attractive in terms of direct conversion architecture. The chapter also describes the design, implementation, and characterization of two SiGe BiCMOS radio front ends.
