Abstract
AbstractThis letter presents a new technique to enhance the overall efficiency of a two‐stage envelope tracking (ET) power amplifier (PA). Because of heavy gain compression, ET amplifiers can suffer from inefficient driver stages. By reducing the supply voltage of the driver amplifier, its efficiency can be improved without degrading the linearity performance of the overall PA system because the final‐stage ET PA allows the decrested RF signal as an input. This technique is demonstrated for a single carrier WCDMA signal using a RF PA based on a GaAs HVHBT with a dynamic supply modulator and a driver stage based on a GaN heterojunction field‐effect transistor (HFET). The measurement shows that the drain efficiency of the driver amplifier is improved from 25.6 to 41.5% and the overall efficiency of the ET PA system is improved from 46.2 to 48.3% while the efficiency of the final‐stage ET PA is maintained at higher than 55%. The average output power is greater than 44.6 dBm, the overall gain is greater than 20 dB, and the adjacent channel leakage ratio is less than −46 and −53 dBc at 5‐ and 10‐MHz frequency offsets, respectively. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 54:505–507, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26527
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