Adaptive Power Amplifiers for Modern Communication Systems with Diverse Operating Conditions
Mahmoud Mohamed, Ahmed
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In this thesis, novel designs for adaptive power amplifiers, capable of maintaining excellent performance at dissimilar signal parameters, are presented. These designs result in electronically reconfigurable, single-ended and Doherty power amplifiers (DPA) that efficiently sustain functionality at different driving signal levels, highly varying time domain characteristics and wide-spread frequency bands. The foregoing three contexts represent those dictated by the diverse standards of modern communication systems. Firstly, two prototypes for a harmonically-tuned reconfigurable matching network using discrete radio frequency (RF) microelectromechanical systems (MEMS) switches and semiconductor varactors will be introduced. Following that is an explanation of how the varactor-based matching network was used to develop a high performance reconfigurable Class F-1 power amplifier. Afterwards, a systematic design procedure for realizing an electronically reconfigurable DPA capable of operating at arbitrary centre frequencies, average power levels and back-off efficiency enhancement power ranges is presented. Complete sets of closed-form equations are outlined which were used to build tunable matching networks that compensate for the deviation of the Doherty distributed elements under the desired deployment scenarios. Off-the-shelf RF MEMS switches are used to realize the reconfigurability of the adaptive Doherty amplifiers. Finally, based on the derived closed-form equations, a tri-band, monolithically integrated DPA was realized using the Canadian Photonics Fabrication Centre (CPFC®) GaN500 monolithic microwave integrated circuit (MMIC) process. Successful integration of high power, high performance RF MEMS switches within the MMIC process paved the way for the realization of the frequency-agile, integrated version of the adaptive Doherty amplifier.