Research On Bandwidth Extension Methodology Of High-efficiency Power Amplifier

Broadband power amplifier (PA) with high efficiency is a current research focus inwireless communication field. The characteristics of modulation signal were studied andseveral broadband and high-efficiency PAs are designed for constant envelope signaland varying envelope signal respectively. The main research contents are as follows:Firstly, a novel approach is presented to build transistor’s matching model anddesign matching networks of a broadband and efficient PA, with which the gain flatnessand linearity can be taken into account. A2-4GHz octave broadband PA is designed andfabricated with10W output power. The power gain is12.3-14.1dB across the bandwhile the power added efficiency (PAE) is36.5-53.4%. Gain flatness keeps less than±0.5dB beyond95%of the band.Secondly, the principle and process of harmonic control are studied thoroughly.Considering the influence of the actual GaN model and nonlinear capacitance, thefundamental impedance and harmonic impedance of class E PA are calculated.Broadband Class E PA based on35W GaN is designed with low-pass filter matchingnetwork. The simulation results show that the PAE up to64-77%in1.7-2.6GHzbandwidth. And the PA was applied to broadband Doherty as a unit.Thirdly, broadband Doherty PA with high back-off efficiency is researched forvarying envelope signal’s system. After analyzing three main factors that limit thebandwidth of Doherty, which are λ/4impedance transformer, output matching networksand offset-line, a parallel Doherty PA is designed. The Doherty achieves6-7dBback-off measured efficiency of36.2-48.8%in the frequency range of1.85-2.25GHzwith saturation efficiency of57.2-68.8%. At1.95,2.05,2.15GHz,9dB back-offefficiency can reach40%.The design method of broadband and high-efficiency PA is described in detail inthis dissertation and two novel PA system schemes are proposed at last. The explorationof broadband Doherty and linear PA system may provide reference for scholars.