Using smaller feature size transistors (< 90 nm) for analog and RF circuits is very challenging. Beside the advantages of newer downscaled CMOS technologies there are also many new difficulties to live with, like decreased voltage headroom, large transistor variability, etc.... To take full advantage of the merits of these new technologies, and to get around the new difficulties, novel concepts for circuits and architectures are investigated. Included are voltage controlled oscillators (VCOs), phase-locked loops (PLLs), low-noise amplifiers (LNAs), analog to digital converters (ADCs), power amplifiers (PAs) and entire transmitters with the emphasis on digital transmitters.