The world of wireless communications is changing very rapidly since a few years. The introduction of digital data communication in combination with digital signal process ing has created the foundation for the development of many new wireless applications. High-quality digital wireless networks for voice communication with global and local coverage, like the GSM and DECT system, are only faint and early examples of the wide variety of wireless applications that will become available in the remainder of this decade. The new evolutions in wireless communications set new requirements for the trans ceivers (transmitter-receivers). Higher operating frequencies, a lower power consump tion and a very high degree of integration, are new specifications which ask for design approaches quite different from the classical RF design techniques. The integrata bility and power consumption reduction of the digital part will further improve with the continued downscaling of technologies. This is however completely different for the analog transceiver front-end, the part which performs the interfacing between the antenna and the digital signal processing. The analog front-end's integratability and power consumption are closely related to the physical limitations of the transceiver topology and not so much to the scaling of the used technology. Chapter 2 gives a detailed study of the level of integration in current transceiver realization and analyzes their limitations. In chapter 3 of this book the complex signal technique for the analysis and synthesis of multi-path receiver and transmitter topologies is introduced.