| Carrier Aggregation(CA)is a technology for effectively increasing transmission bandwidth.In engineering applications,dual carrier aggregation is mainly adopted.The traditional wireless communication transmission technology is gradually replaced by Radio-over-Fiber(RoF)technology due to the disadvantages of limited transmission distance and poor anti-interference capability.RoF technology is a technology that can solve large-capacity information transmission and realize multi-user mobile communication,and it can satisfy the transmission of multi-carrier signals.RoF technology is considered as the sun technology of today's wireless access because it has the advantages of flexible information transmission and strong anti-interference ability.In the dual-carrier aggregation RoF system,the dual-carrier aggregation signal has a very high peak-to-average ratio.When passing through a RoF system,it will generate a strong memory effect and strong nonlinearity,causing nonlinear distortion of the output signal.Therefore,it is of great significance to study the nonlinear model of dual-carrier aggregation RoF system for the development of modern communication.In this dissertation,we study the distortion phenomenon of strong memory effect and strong dynamic nonlinearity after the transmission of the dual carrier aggregatio n signal through the RoF system.The work accomplished by the paper can be divided into three parts:The first part builds the RoF front-end system experimental platform,introduces the characteristics of signal generators,spectrum analyzers,optical modules and power amplifiers of the main components of the experimental platform,and then analyzes the instrument synchronization and data acquisition in the experimental process,followed by The reasons for the non-linearity of the system single-mode optical fiber,optical module and power amplifier are analyzed and studied.The nonlinear distortion phenomenon produced during the experiment is analyzed.Finally,the delay estimation and delay adjustment of the sample data are described.In the second part,the model of dual-carrier aggregation RoF system is described by using memory polynomial(MP)model,generalized memory polynomial(GMP)model and fractional memory polynomial(FMP)model,and the modeling system complexity and modeling accuracy are performed.analyse and compare.In the third part,the digital pre-distortion simulation of traditional memory polynomial,generalized memory polynomial and fractional order memory polynomial for nonlinear distortion of dual-carrier aggregation RoF pre-transmission system is performed to verify the capability of MP model,GMP model and FMP model to describe RoF system.It validates and analyzes the ability of the three predistorter models to suppress the nonlinear characteristics of the dual-carrier aggregation RoF forward system.Finally,a model combining the fractional order memory polynomial and the generalized memory polynomial is proposed based on the three models,and the model of the new model is verified.Describe capabilities and linearization capabilities.The results show that the GMP model has the best ability to describe the dual carrier aggregation RoF pre-transmission system,but the complexity of the MP model and the FMP model system is increased 2.5 times.In the true simulation verification of the system digital pre-distortion method,the GMP model The linearization capability is the best,but actually taking into account the system complexity of the hardware processing,the linearization effect of the FMP model is slightly less than that of the GMP model,but the number of coefficients is reduced by 71%,and the proposed fusion FMP and GMP model The polynomial coefficient is 47% relative to the GMP model,the suppression effect for the third-order intermodulation is increased by 10% to 19%,and the modeling ability and linearization effect are improved. |
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