Research On Linearity Enhancement Of High Efficiency Power Amplifier

As the continuous evolution of modern wireless communication system,the energy efficiency and linearity of terminal transmitter is facing higher requirements.Envelope tracking technology has become a hot spot for PA efficiency enhancement problem,while digital predistortion is the key technique for ETPA linearization.In this paper,we study behaviorial modeling of envelope tracking power amplifier,a envelope tracking memory polynomial model is put forward based on traditional memory polynomial PA model.According to the ETMP model a dual-input digital predistortion method is employed to achieve the goal of comprehensive promotion of ETPA efficiency.Combining ETMP model and the nonlinearity characteristics of dual-band ETPA,a 3D ETMP digital predistortion structure is proposed as an improvement of traditional 2D MP method.For the problem of PA modeling,the traditional single-input PA model is changed into dual-input type based on memory polynomial model and the dynamic supply voltage of ETPA.Both the input signal and its envelope are set as the input variables of this new ETPA model,which is named Envelope Tracking Memory Polynomial model,to implement the dynamic parameter adjustment of traditional memory polynomial model.With the simulation platform on ADS and Matlab,the idea of black box is used for the ETPA modeling with input and output signals.NMSE and ACEPR are compared between traditional ETPA models and ETMP model as the evaluation standard and the accuracy of ETMP model is validated.Based on the ETMP model,the digital predistortion structure of ETPA is improved from single-input predistorter to dual-input predistorter.The high accuracy of ETMP model leads to better linearity and total efficiency with indirect learning structure extracting the model parameter adaptively.With the simulation platform Matlab,NMSE and ACPR are used to evaluate the linearization capability of this ETMP digital predistorter.For the unique nonlinearity and the problem of high ADC sample rate of dual-band ETPA,this paper proposed a 3D ETMP digital predistortion as an enhancement of traditional 2D structure.Based on the proposed ETMP DPD method,the two input signals together with the envelope signal are set as the input variables of the predistorter to improve the linearity of dual-band ETPA.The 3D ETMP DPD system is simulated on Matlab platform and the linearization improvement is validated compared with the dual-band ETPA without digital predistortion.