| In order to make full use of the limited spectrum resources, LTE uses a more efficient modulation techniques such as QAM (Quadrature Amplitude Modulation), but the transmission of non-constant envelope, peak-average ratio signals make the device nonlinear characteristics very sensitive, when the modulation signal generated by the RF power amplifier that will lead to a spectrum spread, channel interference, bit error rate increases and other issues, and some intermodulation distance carriers too close, you can not simply use the filter to filter out. There transmitter RF power amplifier consumes most of the energy, in order to improve the efficiency of the system, the power amplifier is generally in the vicinity of a saturation region, which causes severe signal distortion. Therefore in order to meet the power amplifier linearity and efficiency requirements, power amplifier linearization techniques become a hot research.This paper focuses on the principles of nonlinear distortion amplifier and relevant indicators for analysis, mainly in the form of distortion harmonic distortion, intermodulation distortion and intermodulation distortion, indicators are generally described linearity compression point power, ACPR, etc. And then analyzed the three species improve linearity technology. After the linearization techniques by performing on the analog pre-distortion technology research, using predistortion bicyclic structure, bicyclic structure and nonlinear combination generator, power amplifier module developed analog predistortion module. Based Schottky diodes and field-effect transistors based on nonlinear generators theoretical analysis, prove advantages and disadvantages of the two non-linear generator theoretically finalize analog predistortion based FETs. Analog predistortion can be implemented by a different configuration, the analog predistortion loop structure analysis, select a bicyclic structure. After these studies, finalize select bicyclic structure based FET combining analog predistorter of non-linearity of the power amplifier to be suppressed. System main work is as follows:1. Research the power amplifier nonlinear distortion characteristics, as well as the principle of pre-distortion technology analog predistorter selected specific research programs.2. Based on the theoretical analysis of the Schottky diodes and field-effect transistors based on nonlinear generated to determine the specific type of non-linear generator.3. For different analog predistortion loop structure characteristic determined by comparing the final dual-loop structure.4. Complete the selected simulation-based pre-distortion technology and the overall program design for each feature. |
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