This dissertation focuses on design and implementation of a highly linear and low flicker-noise receiver front-end based on the direct conversion architecture for multiband applications in a CMOS technology. The dissertation consists of two parts: One, implementation of a highly linear RF receiver front-end and, two, implementation of a low flicker-noise RF receiver front-end based for direct conversion architecture. For multiband applications, key active components, highly linear LNAs and mixers, in the RF front-end receiver have been implemented in a 0.18um CMOS process. Theoretical approaches are analyzed from the perspective of implementation issues for highly linear receiver system and are also compared with measured results. Highly linear LNAs and mixers have been analyzed in terms of noise, linearity and power consumption, etc. For a low flicker-noise receiver front-end based on direct conversion architecture, the design of differential LNA and various low flicker-noise mixers are investigated in a standard 0.18um CMOS process. A differential LNA which shows high linearity was fabricated with a low flicker-noise mixer. Three low flicker-noise mixers were designed, measured and compared to the-state-of-the-arts published by other research institutes and companies.