Innovative approaches in Doherty amplifier design for higher efficiency and wider frequency bandwidth

Thesis Type: Doctorate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Engineering, Department of Electrical and Electronics Engineering, Turkey

Approval Date: 2013


Supervisor: ŞİMŞEK DEMİR


In the first phase of this thesis, the design optimizations of the bias adapted Doherty power (BA-DPA) and asymmetric Doherty power amplifier (ADPA) are presented for maximum efficiency criteria in the high power region. BA-DPA is analyzed by a novel approach in terms of efficiency. The ideal efficiency characteristics of BA-DPA with different bias adaptation schemes are illustrated. The maximum conduction angle and periphery requirement of the class-C biased peaking power amplifier (PPA) to realize fully load modulated ADPA are investigated. The appropriate maximum conduction angles and relative peripheries for the PPA are evaluated for different load modulation regions. The advantages and drawbacks of the BA-DPA and ADPA based on the simulated and measured performances of the designed amplifiers are concluded. In the second phase of this thesis, it is focused on the hot research topic of widening the operational bandwidth of the DPA. A novel combiner that solves the fundamental bandwidth limitation problems of the conventional Doherty structure is proposed. A new Doherty amplifier structure with an octave operational bandwidth based on the proposed combiner is presented. The implemented DPA has approximately one and half times higher bandwidth with respect to the similar studies in the literature.