| In order to satisfy the need of communication system to include more users and volume,technical personnel has developed new encoding and modulation technologies such as QAM and OFDM which have high spectrum utilization rate.Because of the high PAPR of this kind of modulation technology,the performance of the communication system has been improved,and power amplifier circuit had serious nonlinear distortion.If the problem is not treated in time,the performance of the communication system will be greatly weakened.Therefore,the linearization technology of power amplifier has become the hot spot of the science and technology workers.At present,there have been various power amplifier linearization techniques such as power regression method,feed-forward,EER method,LINC and pre-distortion method which are suit for different situations and improve the linearity of power amplifier.In order to enhance the adjacent channel power ratio,efficiency and the third order inter-modulation component linear index of power amplifier,feed-forward method,analog pre-distortion and digital pre-distortion linearization technology were studied in this paper.Firstly,the cause and effect of the nonlinear distortion of power amplifier were analyzed,and the nonlinear model of the power amplifier was analyzed.On this basis,the circuit was designed by using the analog pre-distortion method and feed-forward method for GaN RF power amplifier respectively.The simulation of the pre-distortion included input and output full matching and two elimination frequency idea,so that the IMD3 increased by 14.7dB.Feed-forward method made use of the phase matching which made the IMD3 to improve about 27.8dB.In addition,LMS algorithm was used to construct LUT digital pre-distortion system which used amplitude query.Finally,the simulation experiments were carried out with the MATLAB software.The experimental results verified the validity and correctness of the above works. |
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