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학술지 Design and Performance Analysis of Pre-Distorter Including HPA Memory Effect
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안동건, 이일진, 유흥균
Journal of the Korean Institute of Electromagnetic Engineering and Science, v.9 no.2, pp.71-77
한국전자파학회 (KIEES)
09ME2300, MoIP 서비스 기반구조 및 응용 표준개발, 강신각
OFDM(Orthogonal Frequency Division Multiplexing) signals suffer serious nonlinear distortion in the nonlinear HPA(High Power Amplifier) because of high PAPR(Peak Average Power Ratio). Nonlinear distortion can be improved by a pre-distorter, but this pre-distorter is insufficient when the PAPR is very high in an OPFDM system. In this paper, a DFT(Discrete Fourier Transform) transform technique is introduced for PAPR reduction. It is especially important to consider the memory effect of HPA for more precise predistortion. Therefore, in this paper, we consider two models, the TWTA(Traveling-Wave Tube Amplifier) model of Saleh without a memory effect and the HPA memory polynomial model that has a memory effect. We design a pre-distorter and an adaptive pre-distorter that uses the NLMS(Normalized Least Mean Square) algorithm for the compensation of this nonlinear distortion. Without the consideration of a memory effect, the system performance would be degraded, even if the pre-distorter is used for the compensation of the nonlinear distortion. From the simulation results, we can confirm that the proposed system shows an improvement in performance.
KSP 제안 키워드
Average Power, High PAPR, High power amplifier(HPA), Least mean square(LMS), Memory Polynomial(MP), Memory Polynomial Model, Memory effect, Normalized least mean square, Orthogonal frequency division Multiplexing(OFDM), PAPR Reduction, Performance analysis