Investigation of Microwave Power Amplifiers Nonlinearity and Linearization Techniques

Abstract

newline quotThe linearity of power amplifiers plays a major role in the design of communication newlinesystems. At high power levels when power amplifiers are operated near its saturation newlinepower level, the power amplifier s nonlinearity gives rise to signal distortion in the form of newlineharmonics, intermodulation products, etc. The nonlinearity effects are even worse when newlinebandwidth-efficient digital modulation techniques are used. In order to maintain the newlinelinearity, a power amplifier is required to operate in power back off condition but this leads newlineto a decrease in dc to rf efficiency of the transmitter which is not acceptable where power newlinegeneration is costly like in case of on-board satellite transponders. Therefore, to meet this newlinecontraction between linearity and efficiency, Linearization techniques are used. newlineLinearizing is the technique used to improve the nonlinear performance of the newlinecommunication systems when high power amplifiers are operated near saturation condition newlinewithout affecting its efficiency.Therefore, the broadband linearizing technique is required newlineto improve the overall linearity of a broadband communication system for high data rate newlineapplications even though the amplifiers in the transmitter section operate in their nonlinear newlineregion for achieving higher DC to RF efficiency. This research work aims to investigate newlineand design high-frequency broadband linearizer to improve linearity of power newlineamplifiers. In present research work, the study of different linearization techniques has newlinebeen done and diode-based predistortion linearizer is found to be most simple as well as newlinecapable to linearize the power amplifiers for satellite communication applications. The newlinediode-based linearizers using vector modulator configuration are most appropriate for newlinegenerating numerous combinations of amplitude and phase expansion essential for newlinecompensating different SSPA s and TWTA s. The linearizer creates inverse magnitude and newlinephase nonlinearity to that of a power amplifier so as to compensate for its nonlinear newlined