| It has been just three years since the3G business started in China, the number ofnetwork users has exceeded200million. The focus of the wireless communicationindustry has also been transferred to multimedia data transmission from the traditionalsingle voice. IMT-Advanced, the so-called4G is the next world standard of mobilecommunication. Telecom operators in China have started a smooth evolution to one ofthe4G standard, LTE-Advanced.In order to improve the spectrum utilization, OFDMA technology has been widelyused in IMT-Advanced, thus the signal’s PAPR is high. The traditional Class-ABamplifier has very low efficiency for operating in the saturated output power back-offarea. This does not comply with the construction thoughts of green base station andenergy-saving emission reduction, and also reduces the stability and life of amplifiers.In order to meet the IMT-Advanced demand, increase the linearity and efficiency of RFPA become an urgent need to resolve the difficulties of the industry.Among the present common amplifier efficiency enhancement methods, Dohertyamplifier technology has become the research focus of enterprise and academia, becauseof its simple circuit structure, suitable for large-scale production, the design of low-cost,easy linearization, etc.450-470MHz was newly allocated to IMT-Advanced. In this thesis, a450-470MHzRF Doherty PA is designed and implemented, and explored the feasibility of usinglumped parameter network to replace the traditional transmission line. This work issupported by the Major National Science and Technology Project. First of all, this thesisanalyzed the factors which affect the amplifier’s efficiency. Then elaborated on theprinciple of the Doherty amplifier, through the link budget and software simulationdesign, processed and debugged the amplifier circuit board. Finally, after the PA passedthe system verification, analyzed the result.The designed Doherty PA delivers49.2dBm of saturated output power, in450-470MHz, the power gain is38.2dB, and the gain flatness is better than0.2dB. Thesystem test used a LTE-Advanced signal with6.5dB PAPR, at the average output power of42.2dBm, excellent drain efficiency of52%, PAE of48%and-27dBc ACLR beforelinearization were obtained, after DPD linearization, less than-52dBc ACLR has beenachieved. The test results fulfilled and beyond the parameters requirements, whichshows that the designed RF Doherty PA in this paper can be applied to theIMT-Advanced system. |
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