Efficiency enhancement for increasing battery lifetime and its effects such as decreasing cooling costs in communication system base stations has driven RF devices including power amplifiers to operate in nonlinear regions . Nonlinear behavior of RF power amplifiers or RFPAs , as one of the most important components of wireless transmitters , usually limits the RF system's final performance . So a new approach is required to extend linear behavior of PAs to nonlinear regions. In recent decades , there has been several approaches for modeling and designing power amplifiers . In general , all of them use source and load reflection coefficients to design input and output matching networks . These coefficients are set to achieve a specific aim such as maximum gain , maximum output power , minimum noise or a combination of them. One of the most popular approaches is using scattering , [S] , parameters of the transistor . But nonlinearly behaving transistor as a consequence of the input power increasing can't be described by [S] parameters anymore . In another words , [S] parameters lose their validation in nonlinear regions. Among all existing approaches for modeling , analysis and simulation of nonlinear devices , newly defined X-parameters seems to be the best substitute for [S] parameters . Just like [S] parameters , X-parameters model is capable of gathering measurement , modeling and simulation of RF components together in nonlinear region . Despite all efforts made to achieve an analytical framework to be used with CAD tools , there isn't any complete procedure and designing is only available with soft wares like Advanced Design System (ADS) . In this thesis , dir=ltr
