| Within this information explosion era,the requirement of huge amount data from user leads to the rapid development of mobile communication in decades.The trend of transmission speed increase and delay decrease let the high PAR wide-band signal become popular.But this characterization of signal become the root cause,which damage the efficiency and linearity of power amplifier(PA).In the current system,Digital Pre-distortion(DPD)technology is used to improvement the linearity,and Envelope Tracking(ET)technology become popular as the method to make efficiency better.At the same time,during the process of raid iteration of mobile communication standard,Multi standard,and multi band which in used would coexist within the same RF system,Based on the application of Carrier Aggregation(CA)and Muti Input Muti Output(MIMO),leads to the research of concurrent dual-band application at present.The research shows that concurrent dual-band DPD architecture is effective for linearization purpose.This paper focuses on the concurrent dual-band DPD technique which aims to the wide-band power amplifier for different type of realistic application.In this paper,the research includes the following aspects:1.Based on the nonlinearity analysis of PA,research on the nonlinearity within ET system from the envelope and RF signal delay.By using AMAM and AMPM distortion to describe the narrow-band memoryless model lead to analysis of 3rd intermodulation products qualitatively.Also simulating this results in Lab VIEW then verification by using wide-band signal.2.Expand the nonlinearity description in signal band to concurrent dual-band application,notice three of them.Based on the assumption of this two bands are far away enough,so only considering two types of them:IMD and CMD when modeling within the process of DPD.By using 2D-DPD structure which deducing from traditional memory polynomial(MP).We also take DPD in each band in account cause considering one of normal condition that the signals in two bands are same.Cause MP model are widely used in industry,so we also test and verify by using MP model within different DPD structures.3.PXI platform is used as the platform to verify the DPD algorithm.It can be easy setup and use based on the modular instruments,flexible software structure.First discussion is on the hardware choice based on the feature of 2D-DPD structure.After Hardware-in-loop simulation,two kind of Doherty PA on LTE base station on 3.5G band and WCDMA base station are used to verification the effect of algorithm for two kinds of DPD structure.4.Based on the PXI platform discussed above,expanding the hardware to support ETPA is necessary to verify the DPD algorithm with ET.The synchronization is also requested between RF signal generator and Baseband signal generator.Pre-equalization is used to improve the flatness of ETIC and envelop shaping technology is also used to prevent nonlinearity adding into the system.Then,analysis the waveform of concurrent dual-band problem within ET system,after processing the signal then using the DPD technique which discussed above to measure the improvement of system linearity via different DPD structure.2D-DPD shows better performance than other DPD structure in ACP results. |
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