| Since the peak-to-average power ratio modulation signals have been widely used with the advent of 5G era and public have higher requirements for communication quality,resulting in nonlinear distortion of the output signal.In order to ensure linearity,RF power amplifiers are generally required to operate at large power back-off points,which seriously affects the efficiency.On this regard,this thesis proposes a research topic of designing a small and high efficiency RF power amplifier for small-cell & micro-cell base station through In Ga P/Ga As HBT process,which can be used in the 3400MHz?3600MHz band of 5G communication.The main research work and the results are as follows:First of all,the research background and the research status at home and abroad of this topic are sorted out,thus the necessity and importance of this research direction are drawn from the actual situation.Then the In Ga P/Ga As HBT,the core device used in this design,along with the basic parameters and categories of RF power amplifier are introduced in detail.On this basis,the expected performance index of the design are proposed through the consideration of 5G communication standards.Based on the theoretical basis of the circuit construction,the active load modulation of Doherty power amplifier is analyzed.The load variation of the two power amplifiers in different states is quantitatively analyzed through the formula,and the reason for the efficiency improvement is given.Secondly,the simulation and design of power amplifier are carried out.In this circuit,a four-step cascade circuit structure is adopted to ensure sufficient gain,and the high efficiency of power back-off is maintained through Doherty structure,which makes up for the defect of low power utilization caused by multistage amplification.In the sub-circuit function module: the compensation effect of bias circuit to the quiescent current of power amplifier is realized in the temperature from-40? to+110? through the adaptive bias circuit structure,thus reducing its fluctuation amplitude effectively;the power divider is miniaturized and realized easily on chip by replacing the traditional 1/4 wavelength transmission line with lumped parameter element network.In addition,the stability network design,input and output matching circuit design and the cascade process of each level of power amplifier are emphasized in the thesis.The circuit construction of Doherty architecture of two-stage magnification is introduced in detail with theoretical analysis and software simulation.The layout is completed according to the schematic diagram,while the single-tone harmonic simulation,double-tone harmonic simulation and S parameter simulation are carried out jointly with the laminate,then the simulation results are discussed and analyzed.Finally,2?m In Ga P/Ga As HBT process of a compound semiconductor factory is used to tape out,so as to the final physical sample is obtained and tested.The measured results show that the working bandwidth of the power amplifier can reach200 MHz,and its power added efficiency can reach 15.6% and 19.6% respectively at6 d B and 8d B back-off power.In addition,the saturation output power is higher than33 d Bm and the gain remains above 35 d B when the output signal frequency is exactly the center frequency of this power amplifier 3.5GHz.Thus achieving the expected goal of larger gain while maintaining high efficiency. |
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