| In order to further improve the capability of high-speed data transmission in a wireless communication system,it is required that the energy-consuming module in the system has characteristics of more energy-saving and wide frequency coverage.As a module for providing energy and consuming energy in a communication system,the Doherty power amplifier has improved the working efficiency and widened the operating frequency,which has been explored by many researchers.This thesis initially analyzes the development trend of Doherty power amplifiers in recent years by consulting a large number of relevant literatures,and expounds the working principle and performance improvement methods of base station Doherty.Finally,this thesis explores the efficiency and bandwidth performance of Doherty,a wide bandwidth,high efficiency Doherty power amplifier for 5G communication applications is designed.The main work processes are carried out and innovative as follows:Firstly,this thesis reviews the main performance metrics of power amplifiers and focuses on the effects of efficiency and bandwidth on the power amplifier.The working principle of the traditional Doherty power amplifier is deeply studied.The load-pull theory,several working states of the Doherty power amplifier,and the reasons for Doherty's improved back-off efficiency are analyzed,and the great advantage of the Doherty structure is finally confirmed.Secondly,various designs for further improving the efficiency of the traditional Doherty power amplifier were studied and a design method combining the Class F power amplifier with the Doherty power amplifier was finally selected.Firstly,the basic principle of the efficiency improvement of the class F power amplifier is analyzed.Then the feasibility of combining the class F power amplifier with the Doherty power amplifier is discussed,and the combined solution is finally proposed.Finally,the main factors limiting the bandwidth of the Doherty power amplifier are studied.The influence of the impedance transformation line on the working bandwidth of the Doherty power amplifier load modulation network is analyzed,and improved the design concept of the parallel Doherty power amplifier.This concept reduces the fractional bandwidth of the Doherty power amplifier by adjusting the impedance transformation ratio of the impedance transformation line.Finally,a broadband Doherty power amplifier design method that is more compact than a parallel Doherty power amplifier is proposed.At the same time,the new Doherty power amplifier is designed to have a wider bandwidth than traditional Doherty power amplifiers.In summary,this thesis proposes a Class F Doherty power amplifier with a wide bandwidth and high efficiency.It improves the load modulation network to improve bandwidth characteristics.The program is designed to increase the bandwidth and efficiency performance of traditional Doherty amplifiers and design a eomprehensive power amplifier to meet the needs of future 5G communication applications.Under the continuous wave measurements,the power amplifier achieves 61%-71%saturated drain efficiency over the 3.0-4.0GHz frequency range with 6dB back-off efficiency greater than 35%(up to 52%efficiency),and the overall performance of the proposed Doherty power amplifier is superior to traditional Doherty power amplifiers.In addition,in the 3.46GHz to 3.54GHz band,the 20MHz LTE modulated signal is measured and combined with digital predistortion techniques to evaluate its linearization performance.The resulting ACLR value is below-46 dBc. |
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