Optimum spacing for a quadratically interpolated look-up table predistorter for cellular power amplifiers
One of the major barriers in modern wireless communication system is the trade-off between the linearity and power efficiency of cellular power amplifier (PA). On the other hand, the non-constant envelope of spectrally competent modulated signals such as wideband code division multiple access (WC...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
2017
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/77662/1/FK%202017%20134%20ir.pdf |
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| Summary: | One of the major barriers in modern wireless communication system is the trade-off
between the linearity and power efficiency of cellular power amplifier (PA). On the
other hand, the non-constant envelope of spectrally competent modulated signals such
as wideband code division multiple access (WCDMA) and long term evolution (LTE)
interrelates with PA’s non-linearity, causing in-band and out-band distortions. These
distortions violate the out-of band emanation requirements which consequents reduce
the power efficiency. Digital predistortion (DPD) is one of the most promising
techniques to linearize a non-linear power amplifier (PA) in order to reduce the
intermodulation distortion (IMD) and enhance the power efficiency. By far, lookup
table (LUT) predistorters are the most commonly used approach to alleviate the effects
of non-linear PA. This dissertation provides a theoretical analysis of an optimum
spacing of a quadratically interpolated LUT predistorter which reduces the
quantization error introduced by the LUT approximation supported by extensive
simulation experiments. This technique provides better rejection of intermodulation
distortion compared to conventional quadratic interpolated LUT, linear interpolated
LUT and non-linear interpolated LUT predistorters respectively. Simulation results
show that the proposed technique provides an improvement of 20% to 30% of error
vector magnitude (EVM) and an improvement of 3 to 4 dBc of adjacent channel
leakage ratio (ACLR) at a minimal memory usage for the wideband code division
multiple access (WCDMA) and long term evolution system (LTE). This dissertation
also proposes an adaptive Least Mean Square (LMS)-based predistorter that is
optimized for error compensation introduced by LUT interpolation. |
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