Efficient and Wideband Power Amplifiers for Wireless Communications

The rapid evolution of wireless communication systems and the developmentof new standards require that wireless transmitters process several types ofstandards across multiple bands. Power amplifiers (PAs) are key componentsin wireless transmitters because they have a big impact on the overall systemperformance in terms of their bandwidth, efficiency, and linearity. This thesispresents various design techniques that improve bandwidth and efficiencycharacteristics of the PA.For narrowband transmitters, a circuit design methodology that enablesfirst-pass design of high efficiency single-ended PAs is presented. The method,based on employing bare-die transistors, specialized modeling technique, andoptimization of harmonic impedances, is validated with excellent experimentalresults. A class-F−1 PA at 3.5GHz and a harmonically tuned PA at 5.5GHzare designed and implemented demonstrating 78% and 70% PAE respectively.For broadband transmitters, a design methodology for single-ended PAswith octave bandwidth is presented and verified. The method is based on aharmonic tuning approach combined with a systematic design of broadbandmatching networks. The demonstrator PA achieves 50-63% PAE across 1.9-4.3GHz. Then, extending the bandwidth beyond one octave while maintaininghigh efficiency is investigated by adopting a push-pull configuration. For thisreason, a novel push-pull harmonic load-pull measurement setup is proposedand a push-pull PA operating between 1-3GHz is implemented. The investigationdemonstrates the proposed setup as an important tool for understandingand optimizing PAs and baluns for wideband push-pull microwave PAs.For multi-band transmitters, using signals with large peak-to-average powerratio, the design of dual-band Doherty PAs (DPAs) is considered. A detailedanalysis of each passive structure constituting the DPA is given, leading todifferent configurations to implement dual-band DPAs. One of the configurationsis implemented, leading to state-of-the-art results for dual-band DPAs.Finally, the multi-band branch-line coupler (BLC) is a key component for alsoextending the design of DPAs to multi-band in the future. A closed formdesign approach for multi-band BLCs operating at arbitrary frequencies ispresented and validated by the successful design of dual-band, triple-band,and quad-band BLCs.The excellent results obtained demonstrate the success of the developeddesign methodologies for high efficiency and multi-band/wideband PAs. Thesemethods will contribute to the design of future wireless systems with improvedperformance in terms of efficiency, bandwidth and hence cost