| Since 1980 s mobile phoneappeared,wireless communication technology has been developing continuously,and it greatly changes the way of human communication.Power amplifiers(PA)as transmitter components of the highest power consumption,which are required to improve the efficiency and bandwidth of the power amplifier,has been a research hot spot of major study institutions and scholars at home and abroad.Components in 4G and future 5G communication systems are required to performs multi-mode and multi-frequency operation,especially Doherty power amplifiers in the base stationmore are requirced to word in wide bandwidth.Class-J amplifier and Doherty amplifier are deeply researched in the thesis.The main contents and innovations of thethesis as follows:First,according to the basic theory of Class-J power amplifier,based on the Ga N power tube model,a compact structure is adopted in the output matching network.An open fan-shaped microstrip transmission line is used in the output of amplifier instead of the parallel capacitor to compensate the transistor parasitic capacitance Cds.A multi-level low-pass matching network is used in the input matching circuitfor maximum gain matching.A 1.0-3.0GHz Class-J power amplifier circuit is designed to conduct verification experiment,in which a peak efficiency is from55 to 66%,the peak output power is from 40 to 42.6d Bm,gain is more than 10 d B,adjacent channel power ratio(ACPR)is between-24.1 d Bc to-32.4 d Bc,accounting for 100%fractional bandwidth.Second,the frequency coverage of Doherty amplifier is focused on broadening.Firstly,the frequency response and frequency coverage of Doherty power amplifier architecture are discussed.Two kinds of wideband Doherty architectures are proposed according to twofactors that affect the frequency coverage of Doherty power amplifiers.By reducing the impedance transformationratio of?/4 transmission line and shortening the length of the offset line,the frequency coverage of Doherty amplifieris extended and verified through experiments.One of them works at 1.5-2.3GHz,the peak output power is from 42.66 to 44.39 d Bm,the peak efficiency is from 52 to 66%,the 6d B powerback-offefficiency is from 46 to 50%,accounting for 100%fractional bandwidth.Another Doherty power amplifier works at 1.45-2.45 GHz,the peak output power is from 43.81 to 45.43 d Bm,the peak efficiency is from 53 to 63%,the 6d Bpower back-off efficiency is from 40 to 56%,accounting for 51%fractional bandwidth.Thirdly,it is found that when the Doherty power amplifier is theoretically analyzed,it is generally assumed that there is no parasitic parameter at the outputof the powertube,which isequivalent to an ideal current source through the research.However,in practice,the output of the powertube has parasitic inductance and parasitic capacitance which can not be neglected due to the technological problems,the gold wire and the package.For practical power tubes,two new design methods are proposed in this chapter to achieve good load modulation by designing the total electrical length of the output circuit of the two branches of carrier and peak to a fixed electrical length.The Ga N HEMT power tube is used to achieve two Doherty amplifier circuit for theoretical verification.One of the operating frequency bands is 1.9-2.4GHz,the peak output power is from44.2 to 45 d Bm,the peak efficiency is from 63 to 71%,and the 6d Bback-offefficiency is more than51%,and the linearity is good.The other is Three-device Doherty amplifier circuit whose frequency is from 1.45 to 2.35 GHz,the peak output power is from 44.3 to 46.8d Bm,the peak efficiency is from 58 to 70%,the saturation gain is more than 8d B,the 9d Bpower back-off efficiency is from 40 to 54%,accounting for 46%fractional bandwidth.The thesis presents a compact Class-J power amplifier and multiple broadband Doherty power amplifier architecture.In addition,a 5G Doherty power amplifier increasing video bandwidth(VBW)is proposed and designed aiming at the peak-to-average modulation signal,which provides some references for the development of wide modulation bandwidth Doherty power amplifier circuit in future communication systems. |
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