Power Amplifier Behavioral Modeling Algorithms for Digital/Hybrid Predistortion in Software Defined Transmitters
Date
2014-10-02
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Abstract
Power amplifier (PA) is a vital component of transmission system and effect of PA nonlinearity and memory effects are generally investigated in system level analysis of communication systems. Among time and frequency domain approaches, time domain behavioral modeling is more popular as it also considers memory effect and it finds useful application as inverse modeling for digital predistorter to enhance the signal quality. Among many models, Memory polynomial (MP) model is still considered as most simple and effective parametric model as it provides best modeling performance with less complexity.
This thesis investigates two models, which aim to improve stability and accuracy of memory polynomial model. The proposed Pseudo Zernike Memory polynomial (PZMP) model is modified version of the Zernike polynomial function, which provides more robust performance in terms of better condition number and dispersion coefficients for PA behavioral modelling, with respect to previously proposed models such as orthogonal memory polynomial (OMP) and MP model. It provides approximately,
i) . 75% and 50% improvement in terms of dispersion coefficients (in dB) over MP model and OMP model respectively; ii). 61% and 15% improvement in terms of condition number (in dB) over MP model and OMP model respectively.
The other model takes advantage of recursive property of Rational Polynomial (RP), which is closer to the physical analogy of PA. The proposed model retrieves data in two steps to maintain causality of the system. The proposed two-step-rational polynomial model improves modeling performance in terms of in-band and out-of-band performance and provides far better modeling as compared to memory polynomial model.
This thesis also includes the study of hydrid digital predistortion (DPD) technique for complete RF-in and RF-out system. The system is implemented in Field-Programmable Gate (FPGA) using Look-Up Tables (LUT). The compensation of the I-Q (Inphase-Quadrature phase) imbalance in the setup is further studied for such system.
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Engineering--Electronics and Electrical
Citation
Rawat, P. (2014). Power Amplifier Behavioral Modeling Algorithms for Digital/Hybrid Predistortion in Software Defined Transmitters (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/27392