Research On Doherty Power Amplifier

In this thesis,a 2.6GHz band Doherty power amplifier which will be applied for base station communication had been researched.Because of its feature of high efficiency over an extended power range,the Doherty power amplifier(DPA)become more and more significant candidate for this type of application.But in the actual application,DPA often failed to exhibit the superb efficiency predicted by theory and their linearity can not meet the strict specifications of systems with high Peak-to-Average Ration(PAR)signals.Firstly,the thesis summarized the status and development trend of Doherty power amplifier in China and abroad.Secondly,introduces the work status and main performance indexes of power amplifier.Then according to the data about the optimized load pull from datasheet with MOSFET A2T26H160-24S which Freescale provided,we did the simulation with input and output impedance network and which can supply a accurate and stable matching circuit for the subsequent design.Parameter extraction of an equivalent circuit model for the transistor is carried out and load-pull is simulated based on the created model to get the optimum load impedance.By comparing the optimum load impedance tested that the datasheet of the transistor offers with the optimum load impedance simulated.Based on the above,we designed a DPA that lead to a simultaneous high efficiency and high linearity performace,finished the PCB designing,soldering,trimming,testing,then compared and analysised the test data with simulated data.The 2.6GHz Doherty power amplifier is mainly designed using ADS software in this thesis.By simulating and optimizing schematic and layout,the gain of small signal of 2.6GHz Doherty power amplifier is higher than 16dB.When working on the large signal,the average output power is 44.5dBm,power gain is bigger than 15dB,and DE high than 40%,the maximum saturated output power is 51.9dBm.When maximum output back off is 7.4dB,the drain efficiency(DE)can still achieve 40%.It shows that the designed Doherty power has a good performance.The results of the test data show that the designed Doherty power amplifier has achieved the expected specifications.