| Under the craze of 5G technology,the nerves of the entire wireless communication industry will be affected by any news about 5G.As the next-generation wireless communication network,5G has a higher network transmission rate than the currently popular 4G LTE,and can reach hundreds of times as fast as 4G.One of the big innovations in 5G technology is the application of Massive MIMO technology,which greatly increases the capacity and bandwidth of communication.Using Massive MIMO technology means that there are many channels of power amplifiers and a large number of antennas are used,making the design more complicated.These changes place higher demands on the performance of the power amplifier,not only to achieve high efficiency in the wide frequency range,but also to ensure high back-off.In the early stage of this thesis,through reading a large number of relevant literatures,the main research points of the researchers in this field are summarized,the principle of Doherty and Outphasing power amplifier technology are expounded.Finally,the power amplifier and power combiner part are highlighted in this thesis,a broadband and high back-off Doherty-Outphasing power amplifier is designed.Firstly,various performance improvement techniques in power amplifiers are systematically classified,and this thesis focuses on the discussion of Outphasing power amplifier and Doherty power amplifier.After analyzing the theory of Outphasing technology,the two modules of power amplifier and combiner in the analog circuit part are introduced.High efficiency power amplifiers are used in the conventional Outphasing power amplifier circuit,which needs to always work in saturation state.However,the gain will be compressed in the saturated state.When the gain is not high enough,the signal is not only easy to be distorted,but also the power added efficiency(PAE)is greatly reduced.The Doherty power amplifier is used in Outphasing technology to amplify two input signals in this thesis,so that it can maintain high efficiency in the case of high back-off when the power amplifier is in an unsaturated state.The factors limiting the bandwidth of Doherty power amplifier are analyzed,and how to realize bandwidth expansion is introduced.A Doherty power amplifier with broadband characteristics is designed and processed.According to the actual measurement,the broadband Doherty of this design has an average output power of 43 d Bm over the frequency range from 2.8GHz to 3.8GHz,a saturated drain efficiency of 62%-68%,the drain efficiency at 6d B back-off is higher than 38%.Starting with the Outphasing combiner,the non-isolated Chireix combiner is analyzed to design a combiner with broadband characteristics,the broadband Doherty and the modified Chireix combiner are combined to improve the overall Outphasing power amplifier.The simulation results shows over the frequency range of 3.0GHz-3.8GHz,the saturated output power is 46.5-47.5d Bm,the saturated drain efficiency is 56%-68%,the efficiency is 45%-55% and maintained above 35% at 6d B and 10 d B back-off respectively,which indicates that the design of Doherty-Outphasing has broadband and high back-off characteristics. |
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