چکیده:
In this paper, a novel technique is proposed for linearizing digital pre-distortion in power
amplifiers for OFDM systems. For this purpose, a hybrid technique comprising search table
method and polynomial method is employed such that as few as hardware are utilize in
implementation in order to not only decreases computational complexity but also leads to a
fast response capability. Furthermore, least mean square (LMS), as a competitive method,
was employed in the proposed technique. Coefficients of look-up table are estimated by LMS
method as a forward program with the least error amount in order to estimate modulator
output of OFDM. In addition, designing of several RF power amplifiers and their
linearization unit in ADS software results in elimination of non-linear distortions of these
amplifiers by linearizing unit, and yet various realistic involved phenomena in base-band
pre-distortion system design, including memory effect, antenna mismatch, and etc., are
studied. Measures such as ACPR were adopted for the purpose of linearization
measurement and comparison. High The peak-to-average power ratio (PAPR) is one of the
biggest problems in OFDM systems that by combining these techniques, we improve it. The
obtained results of the proposed technique are presented both by look-up table and
frequency spectrum of output signal. The results also indicate appropriate performance of
the proposed technique. Simulations were carried out on ADS software, while final signal
output was extracted by MATLAB.
خلاصه ماشینی:
"Keyword: Digital Pre-distortion, Power amplifier, Linearization, OFDM, Look-up table method, Polynomial method * Corresponding author: Mahsa Shokri Peer review under responsibility of UCT Journal of Research in Science, Engineering and Technology INTRODUCTION In recent years, many attentions have been paid on high spectrum performance by many digital radio system designers.
In this paper, a novel hybrid method comprising polynomial method and Look-up table method is used in order to linearization pre-distortion in power amplifiers based on the proposed adaptive LMS algorithm.
Appendix LMS: Least Mean Square DPD : digital predistorter OFDM : Orthogonal Frequency-Division Multiplexing PAPR : Peak to Average Power Ratio DSP : Digital Signal Processing Lut: look-up table RF : Radio Frequency FPGA : Field-Programmable Gate Array SED-DPD : slow envelope dependent digital predistorter PA : Power Amplifier IMD : intermodulation distortoin QAM : quadrature amplitude modulation MS-DPD : mixed-signal digital predistorter PLUME : Parallel-LUT-MP-EMP 2-D-MSP : Two-Dimensional Memory Selective Polynomial GMP : generalized memory polynomial TNTB : twin nonlinear two-box FTNTB : Forward twin nonlinear two-box RTNTB : reverse twin nonlinear two-box PTNTB : parallel twin nonlinear two-box CCDF: Complementary Cumulative Distribution Function CDF: Cumulative Distribution Function DAC : Digital to analog converter ADC : Analog to Digital converter ACPR: Adjacent Channel Power Ratio CPD : cuber predistortion ET : Envelope tracking LINC : linear amplification with non-linear component BPC : basic predistortion cell PT : polar transmitters MSE : mean square error References [1] Ahmed Birafane, Mohamad El-Asmar, and Ammar B."