Research And Design Of Continuous Class-F Mode Power Amplifier

With the development of wireless communication technology,the requirements of wireless system for power amplifiers(PAs)performance is higher than before.This makes PAs with broadband and high efficiency to be a hot spot of research.Focus on this problem,continuous class-F PA theory is proposed in 2010.The theory of continuous class-F PA is to replace a single matching point with high efficiency impedance space to achieve high efficiency over a broadband.However,the continuous class-F PA usually exists weaknesses of poor flatnesses of gain and drain efficiency in wide working frequency band.In addition,traditional design method ignores the harmonics impedance control networks of source end.For these reasons,this paper conducts a study on continuous class-F PA.The possibility of the application of using negative feedback structure in continuous class-F PA is studied in this paper.Negative feedback structure from drain to gate is added to continuous class-F PA,which is with the purpose of reduction the gain and efficiency of the efficiency in low-frequency part to compensate those in high-frequency part of the PA so that gain and efficiency flatness are increased.At the same time,the method of multi-harmonic bilateral pull is used in analysis process to eliminate the mutual influence between source impedance and load impedance.Also by using this method,fundamental and harmonics impedance of each frequency point are studied for finding their high efficiency impedance region.The second harmonic source impedance is studied particularly.The specific contents of this paper are as follows:1.The basic theory of continuous class-F PA is summarized systematically.Drain vltage and drain current waveforms is presented and analysed to explain the principle of continuous class-F PA harmonics controlling.In addition,continuous operation mode and impedance space is illustrated to explained the reason why continuous class-F PA is broadband;2.Negative feedback circuit using in PA is studied.The effect of adding negative feedback circuit in PA is analyzed.And a continuous class-F PA with negative feedback circuit is designed;3.Source and load fundamental and harmonics impedance of each frequency point are studied by using multi-harmonic bilateral pull.The influence of source second harmonic impedance on efficiency is studied particularly.High efficiency impedance region of each frequency point is found;4.Experiments are made to verify the feasibility and effectiveness of the proposed design method.The results show that the performance of the continuous class-F PA with negative feedback structure reaches the expected.The measured PAE varies between 62% and 68% and gain varies between 9.7d B and 10.8d B which show good gain and efficiency flatness over 1.5-2.5GHz band.The research of this paper has reference value for research and engineering application of boardband with high efficiency amplifier.