Study On RF Power Amplifier

With the development of wireless communication technologies, the design demand of wireless communication equipment is more and more high. As one of the most important blocks in transmitter, the performance of RF power amplifiers restricts the technique level of the whole system. High linearity and high efficiency are critical issues of power amplifiers. ADS software was used to design PA, together with the Freescale's LDMOS transistor. The design process of PA was discussed and has designed and implemented RF power amplifier of base station with high power adding efficiency, which can be applied in GSM EDGE and GSM system. Meanwhile, the branch-line coupler and power divider were combined with PA to make up a balanced amplifier. Finally, the PA was applied to research Doherty power amplifier with high linearity and high efficiency. The works included in this paper are as follows:Firstly, the work states and parameters of RFPA were introduced, the bias circuit technique, stable technology, nonlinearity analysis methods, improvement technologies of PA performance, the property of LDMOS transistor were researched in detail.Secondly, the design flow of RFPA was given. The process of PA was finished by means of ADS software, Load-Pull method was applied to meet the design demand. Thirdly, the structure and function of balanced amplifiers were researched. Balanced amplifier can increase the out power and improve the linearity of normal PA.Finally, Doherty power amplifier was introduced, whose theory and work state were analyzed. A dipole Doherty power amplifier was designed, which could increase the power adding efficiency 15 percent compared to balanced amplifier.