Research And Realization Of Digital Predistortion In Multi - Carrier Transmission

The multi-carrier aggregation technology which is widely used in modern communication systems can polymerize a plurality of discrete spectrum resource and transmit, but the transmitted signal has a high peak-to-average ratio. The modulated signal which has a high PAPR put forward higher requirements for the amplifier design, and sometimes RF amplifiers even cannot be designed to meet the requirements of the modulated signal. Moreover, modern communication systems tend to adopt non-constant envelope modulation, which is very sensitive to nonlinear effects of RF power amplifier. So it has important significance to study the achievable combination of crest factor reduction and power amplifier linearization.The multi-carrier aggregation signal has the characteristics of high PAPR, in view of this problem, peak cancellation crest factor reduction algorithm (PC-CFR) is selected to realize through different PAPR reduction algorithms simulation contrast. Next, power amplifier linearization techniques study and adopt the memory polynomial digital pre-distortion (DPD) scheme. The implementation architecture of DPD is determined, and the time delay estimation algorithm for the method of minimum amplitude difference is introduced in this paper. Finally, the multi-carrier aggregation, PAR reduction and DPD have a hardware implementation. For adaptive algorithm in DPD module, this paper adopts the QRD-RLS algorithm implemented in hardware, and elaborates the FPGA implementation with the systolic structure based on plural Givens rotation in detail.Finally the off-line test on the DPD in combination with crest factor reduction is given. The results show the two-stage iterative scheme is used to reduce its PAPR form 9.4dB to 6.5dB. The ACPR improvement of power amplifier output with DPD based on memory polynomial reaches 20dB, but that of the DPD without CFR is low around 13dB, and this directly verifies that the DPD module in combination with CFR improves the effect of the linearization, this once again demonstrates the effectiveness and feasibility of the scheme.