الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Power amplifiers (PAs) are key components in wireless communication system transceivers. Their function is to amplify RF signal to a required RF power level that allows transmission of signal to an appropriate range. Linear power amplifiers (LP As) are of importance and very needed in the modem wireless communication systems that deploy non¬constant envelope modulations (e.g. CDMA and OFDM systems).
A power amplifier is a circuit for converting DC input power into a significant amount ofRF/microwave output power. In most cases, a PA is not just a small signal amplifier driven into saturation. There exists a great variety of different PAs, and most employ techniques beyond simple linear amplification, as a critical module in the transmit chain; it is typically the final stage of a transmitter to drive antenna.
A radio frequency PA has the role of amplifying a modulated signal to obtain a specified output power level. In effect, an RF PA converts the DC energy from a power supply to an RF energy sent to an antenna, thus it can be thought of as a DC to RF energy converter. The efficiency of this energy conversion, the quality of conversion, the level of output power, and the linearity are all among the important characteristics of the P A.
Power amplifier circuits commonly are classified as A, B, AB and C classes for analog circuit designs, and D and E classes for switching circuit designs.
A cQmmon disadvantage of LPAs compared to their nonlinear counterparts is their substantially lower power efficiency. Since the PA is the component that consumes most of the power in a transmitter, this lower power efficiency directly translates into lower talk time in portable communication systems. Therefore, improving efficiency of LPAs is a major objective. Finding fast and systematic nonlinearity analysis methods and tools as well as linearization techniques that promise higher efficiency are among the major challenges along this way.