SiWatt is a cooperation R&D project between KIT and milli IC GmbH focused on developing highly efficient Si-based power amplifiers (PA) with output powers comparable to III-V technologies such as GaAs. KIT focuses on investigating the possibilities of improving the linearity of PAs based on the resonant cores idea developed at KIT for enhanced communication capabilities. Techniques including derivative superposition, adaptive biasing and stacked resonated cores are being explored.