High-efficiency and high-linearity silicon germanium BiCMOS power amplifiers for WCDMA handset applications

In recent years, silicon germanium (SiGe) has become a competitive candidate for the development of cellular handset power amplifiers (PAs) of third-generation (3G) wireless communication systems, since SiGe exhibits good linearity, low-cost and compatibility with BiCMOS technology. Wideband Code Division Multiple Access (WCDMA), one of 3G cellular system standards, promises wideband services and high data rate applications, such as video teleconferencing and web browsing. This poses stringent requirements on efficiency and linearity of RF handset power amplifiers (PAs).; This dissertation proposes switched dynamic biasing techniques to boost the average power efficiency of WCDMA power amplifiers. Furthermore, the gain-variation issue in the existing dynamic biasing techniques is overcome by keeping the collector current density constant, which further helps with the error vector magnitude (EVM) of WCDMA handsets. Two prototype WCDMA handset PAs have been implemented in a 0.25 mum SiGe BiCMOS process to demonstrate the effectiveness of the proposed techniques.; The linearity of SiGe HBT power amplifiers has been analyzed with power-dependent coefficient Volterra (PDCV) analysis. A SiGe HBT power amplifier is analyzed to identify the dominant sources of nonlinearity and provide directions to design linear SiGe HBT high-power amplifiers. A dynamically-biased RF amplifier with envelope signal injection is also analyzed to clarify the cause of third-order intermodulation product (IMD3) asymmetry. Furthermore, the linearity of the amplifier can be improved by optimizing the phase and amplitude of the injected envelope signal. Both analyses are confirmed with simulation and experimental results.; Digital predistortion is employed to improve the linearity of WCDMA power amplifiers, since it can be conveniently integrated, flexibly controlled, and economically implemented without sacrificing other performance, such as power gain and efficiency. The operation principle of digital predistortion is derived rigorously. The effectiveness of digital predistortion is verified through experimental results.