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FULLY DIGITAL - NO PUBLIC : PhD Defence Ali Ghahremani | Switch-mode class-E power amplifiers: A contribution toward high performance and reliability

Switch-mode class-E power amplifiers: A contribution toward high performance and reliability

Due to the COVID-19 crisis measures the PhD defence of Ali Ghahremani will take place online.

The PhD defence can be followed by a live stream.

Ali Ghahremani is a PhD student in the research group Integrated Circuit Design (ICD). His supervisor is prof.dr.ir. B. Nauta from the Faculty of Electrical Engineering, Mathematics and Computer Science (EEMCS).

Switch-mode class-E Power Amplifiers (PAs) have shown great potential for efficient amplification of RF signals. Thanks to the switched-mode operation, class-E PAs are CMOS-friendly and show a weak dependency on process variations. However, due to incorporating tuned tanks, the dependency on the load impedance is relatively large, resulting in load-dependent power, efficiency, peak voltages and currents which can lead to reliability issues. The first part of this thesis presents load pull analyses for class-E PAs including effects of the most common non-idealities of this class. 

To enable amplitude modulation, outphasing technique was employed. Next, this thesis presents an analysis of outphasing class-E PAs (OEPAs), using load-pull analyses of single class-E PAs. This analysis led to an approach to improve the deep power back-off efficiency of OEPAs, to improve the output power dynamic range and to reduce switch voltage stress. The theory was validated using a 65nm CMOS demonstration using an off-chip power combiner.

For high back-off efficiency of OEPAs, non-isolating power combiners are required. In the third part of this thesis the linearity of OEPAs using non-isolating power combiners is studied theoretically and validated experimentally. The developed theoretical model for the linearity is then employed to define digital pre-distortion parameters which enables a competitive linearity performance compared to the state of the art OEPAs without any AM/AM and AM/PM characterization requirements.

Finally, this thesis introduces a technique to self-protect Class-E PAs against the effects of load variations. It is shown that the proposed self-protective PA can reduce its peak switch voltage to safe operating conditions for all load mismatch conditions with VSWR up to 19:1 while output power and efficiency are not considerably affected.

Overall, this thesis contributes to design of high performance and reliable switch-mode class-E PAs.