Continuous-Mode Power Amplifiers for Broadband Power-Efficient Wireless Applications

Date
2015-02-02
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Abstract
Radio Frequency power amplifiers (PAs) are key elements in transmitters of wireless radios. Their main task is to amplify the signal and generate the required output power that allows transmission and radiation of the signal over the appropriate range. PA requirements mainly consist of the absolute achievable output power in conjunction with the highest possible efficiency and signal quality performances. Large bandwidths are also important requirements for PAs in contemporary and future communication systems. In this dissertation, a continuous-mode PA concept for achieving the best possible power and efficiency across wide bandwidths is investigated and a thorough study is carried out to assess the impact of practical device voltage limitations on the PA performance. A comprehensive analysis of the extended continuous class-B (class-J) mode is carried out and led to the development of a graphical tool, called "linearity contour", whose role is in identifying the PA load impedance design spaces. Taking advantage of the class-J PA and considering the impact of the output matching network's inductor loss, a methodology is proposed for the design of an integrated GaN class-J PA. To improve further the PA bandwidth, an on-wafer loadpull setup is arranged to measure the required load impedances. Measurement results of the PA show a 25\% bandwidth improvement in comparison with the conventional design approach. In addition, a design methodology to present the required class-J impedances is proposed and verified by designing a class-J PA with a die transistor. The study of the continuous-mode PAs is extended to the class-C mode by proposing a low- and a high-power continuous class-C mode and demonstrating experimentally their RF performances for a set of load impedances across certain design spaces. Examples of GaN MMIC PAs working in continuous class-C modes are provided to validate the proposed concept. Finally, to improve the linearity of PAs that present dual inflection points in their AM/AM characteristics, such as GaAs and GaN based amplifiers, an analog predistortion linearizer is proposed. By adjusting three Schottky and PIN diodes bias voltages in the implemented predistorter, the reverse AM/AM characteristic of a PA is synthesized and used to linearize the PA.
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Engineering--Electronics and Electrical
Citation
Rezaei Nazifi, S. (2015). Continuous-Mode Power Amplifiers for Broadband Power-Efficient Wireless Applications (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/25441