Research On Behavioral Models And Digital Predistortion Of Concurrent Dual-band Power Amplifiers

With the evolution of wireless communications,communication systems have to support more frequency bands and more communication standards at the same time.As an important component of transmitter,power amplifiers(PAs)also need to meet this requirement.In order to solve the tradeoff problem between efficiency and linearity of PAs in this situation,it is necessary to adopt dual-band or multi-band power amplifier linearization technology.In recent years,concurrent dual-band digital predistortion(DPD)has been one of the research focuses on power amplifier linearization technology.Similar to the case of single band DPD,the nonlinearity of PAs is determined by the behavioral model of dual-band PAs.This thesis mainly focuses on the behavioral model of dual-frequency PAs and DPD technology.The main work is as follows.Firstly,the numerical instability is analyzed theoretically when least square(LS)method is used to extract the 2D-DPD model coefficients of dual-frequency PAs.To solve this problem,the sparsity between the coefficients and basis functions in single-band PA models is extended to dual-band.The orthogonal matching pursuit(OMP)method of compress sensing technique is adopted to the concurrent dual-band PA modeling and DPD.The proposed method is validated by the experiment when the PA is excited by the 40-MHz 4-Carrier LTE signal.Compared with the LS method,the proposed method can provide nearly the same modeling and DPD performance,but with lower complexity and better stability.Secondly,a novel 2D-CPWL model is propsed by combining the canonical piecewise linear function(CPWL)with the 2D-MMP model.In the 2D-CPWL model,higher order terms in the 2D-MMP model are replaced by the CPWL functions,so the model structure is simpler.Experimental results show that nearly the same model accuracy and linearization effect can be achieved by the 2D-CPWL model and the 2D-MMP mode,but the 2D-CPWL model has fewer coefficients with a smaller amplitude range.Besides,the 2D-CPWL model requires less hardware resources and does not include magnitude(square root)operations,so it doesn't need to implement CORDIC algorithm module and the difficulty of hardware implementation of dual-frequency DPD model will be greatly reduced.Finally,a broadband continuous inverse class F power amplifier is designed with the CGH40010 GaN HEMT.The simulation and experimental results show that the PA can operate form 2.2GHz to 3.4GHz and over 35 dBm maximum output power and over 60% efficiency can be achieved.The PA can be used to verify the DPD behavioral model and its algorithm of the concurrent dual-band power amplifier.