This text brings together information about the design, modelling and measurement of optimised integrated varactors for Radio Frequency applications. Starting with a full introduction to the technology, including Quality (Q) Factor, and a look at future perspectives, the authors go on to examine typical PN and MOS type varactor models in more detail. Also, the reader is introduced to a novel wide band model, especially useful for the design of Ultra Wide Band (UWB) circuits. Following this, measurement and de-embedding techniques are explained, in order to achieve complete characterisation of integrated varactors for RF applications. The next two chapters systematically cover design rules and the modelization of PN and MOS type varactors, before finally setting out the components and design of a complete Voltage Controlled Oscillator (VCO) circuit.