Research And Implementation Of Asymmetric Doherty Power Amplifier

With the rapid development of wireless communication industry,in order to satisfy faster data transmission rate,the bandwidth of communication signal requires wider and wider.Along the surge of modulation bandwidth,high efficiency spectrum modulation technology is applied to solve the problem of spectrum congestion.However,the modulated transmission signal has a higher peak-to-average power ratio?PAR?,and the higher PAR signal proposes a more severe challenge for the power amplifier to maintain good efficiency and linearity.Based on this background,this paper deeply studies the efficiency of traditional Doherty RF power amplifiers and designs an A_Doherty?asymmetrical Doherty?power amplifier based on this research,the research work is summarized as follows:1.The working mechanism of the traditional symmetric Doherty RF power amplifier is studied,and its inherent defects are analyzed in detail.Aiming at its inherent defects,four improved methods were introduced,and the principles of four improved methods were analyzed.Guided design of the A_Doherty power amplifier2.A 4dB unequal power divider is designed to solve the problem that the Doherty power amplifier is different from the fundamental output current of the carrier power amplifier and the peak power amplifier at the saturation power.The"unequal power input"structure is used in the input terminal of the A_Doherty power amplifier.The reflection coefficients of all ports of the unequal power divider are all less than-15dB,and the port isolation is greater than 20dB.3.In order to eliminate the adverse influence of harmonic power on the efficiency of A_Doherty power amplifier,an output matching network with harmonic suppression function is designed.The output matching port reflection coefficient is less than-15dB and the second harmonic rejection capability is greater than 20dB.4.A new A_Doherty power amplifier is designed with the structure of"unequal power input"and"harmonic suppression".In addition,the measurement results of A_Doherty power amplifier and traditional symmetry Doherty amplifier and AB class amplifier are analyzed and compared.According to the comparison result,the additional efficiency of the A_Doherty power amplifier designed in this paper is significantly improved,which verifies the correctness of the design of this paper.The final test results show that the saturated output power of the A_Doherty power amplifier can reach 39.5dBm,the output power ₁P dB compression point is 40.6dBm,and the additional efficiency at the saturated output power is 45.74%.When the power return is 6dB,the additional efficiency is 37.68%.Therefore,the A_Doherty power amplifier designed in this paper satisfies the design specification requirements and has good performance.