Efficiency Improvement of WCDMA Base Station Transmitters using Class-F power amplifi
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06-10-2010, 03:33 PM
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Efficiency Improvement of WCDMA Base Station Transmitters using Class-F power amplifiers
Universal Mobile Telecommunications Systems (UMTS) is the preferred third generation (3G) communication standard for mobile communications and will provide worldwide coverage, a convenient software technology and very high data rate. The high data rate, especially, requires the use of bandwidth-efficient modulation schemes such as Quadrature Phase Shift Keying (QPSK). But modulation schemes such as QPSK need, in turn, a very linear power from the output of the transmitter power amplifier in order to meet the spectral requirements. A linear power amplifier, traditionally, has very low energy efficiency. Poor energy efficiency directly affects operational costs and causes thermal heating issues in base station transmitters. Thus the power amplifier designer is forced to trade-off between linearity and efficiency. As a result of this trade-off a Class-AB power amplifier is most often used in QPSK based systems. Class-AB power amplifiers provide acceptable linearity at efficiency values around 45-50% typically. This compromise is not a satisfactory solution but is inevitable while using traditional power amplifier design techniques.