Research On High Linearity Power Amplifier Based On Three-way Doherty Technology

Power Amplifier(PA)is one of the core modules in modern wireless communication systems,and its performance directly affects the parameters of the entire system.The development of wireless communication systems makes signal modulation methods change with each passing day.At the same time,the update of coding schemes makes the signal envelope time-varying,and the large peak-to-average ratio signals generated have higher requirements for power back-off range,efficiency,linearity and other indicators.Based on the above application background,this article proposes a three-way Doherty power amplifier with a new unequal division three-way Doherty power amplifier and a reconfigurable power distribution structure.The main work of this thesis is as follows:Firstly,this thesis briefly introduces the main performance parameters and classification of RF power amplifier,studies the classical structure and working principle of Doherty power amplifier,and further analyzes the working mechanism and basic principle of three-way Doherty power amplifier in two different structures.Secondly,a new type of unequal three-way Doherty power amplifier is proposed.Compared with the traditional three-way Doherty structure,this scheme maintains a higher efficiency and linearity index in a larger power back-off range.The operating frequency is 2.5 GHz-2.7 GHz,and the saturation output power in the simulation results is 51.4 d Bm.The Power Added Efficiency(PAE)is 40.2% when the power is back to 9d B,and the Third Order Intermodulation(IMD3)can maintain-45 d Bc.The test results show that when the power amplifier is working at the center frequency of 2.6 GHz,the saturated output power is 51.1 d Bm,when the power is back 9 d B,the PAE is 36.3%,and the Adjacent Channel Power Ratio(ACPR)index is-37.7 d Bc.Finally,aiming at the defects of the unequal three-way Doherty power amplifier,such as the irreconcilability and poor flexibility,this thesis proposes a three-way Doherty power amplifier based on reconfigurable power distribution structure.The structure realizes the adjustability of power division ratio and phase by adjusting the reverse bias DC bias of the varactor diode of the bridge.The test results show that when the power amplifier is working at the center frequency of 2.6 GHz,the saturation output power is 51.2 d Bm,the PAE is 42.2% when the power is back to 9 d B,and the ACPR is-40.3 d Bc.Compared with the unequal three-way Doherty power amplifier,the linearity index of the three-way Doherty power amplifier with reconfigurable power distribution structure is greatly improved,which verifies the feasibility and rationality of the proposed circuit structure.In this thesis,two kinds of Doherty power amplifier are designed by using the new unequal three-way and reconfigurable power distribution structure.Under the premise of high efficiency,the linearity of the power amplifier is improved,which provides a new idea for the research of Doherty power amplifier linearity design in the future.