Power amplifier memory polynomial predistorter for long term evolution application
In Radio Frequency (RF) Front-End wireless communications systems, the power amplifier should be efficient in order to support more users and leads to decrease the costs of energy, and to extend the duration of the battery life, accordingly. Modern digital modulated signals like: Long Term Evo...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
2015
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/68099/1/fk%202015%20125%20ir.pdf |
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| Summary: | In Radio Frequency (RF) Front-End wireless communications systems, the power
amplifier should be efficient in order to support more users and leads to decrease
the costs of energy, and to extend the duration of the battery life, accordingly.
Modern digital modulated signals like: Long Term Evolution (LTE) and Universal
Mobile Telephone System (UMTS) exhibit difficult challenging concerns on
the efficiency of the radio frequency power amplifiers and their design. Despite
the spectral efficiency of these new modulated schemes, the RF PAs which are
excited by the modulated signals like LTE, can experience nonlinear and unstable
situation. These situations cause distortions and then result in lots of drawbacks
like: power loss or heating. Therefore, some linearization techniques have been
proposed to overcome the effects of non linearity. The designer can implement
the digital predistortion and apply it to the input of the amplifiers for the top
speed digital processors. This solution represents a significant paradigm shift for
design and compensation of the nonlinear RF PAs. In this thesis, some behavioral
modeling approaches of the nonlinear dynamic distortions in the wireless
communication systems are investigated to model RF nonlinear PAs in order to
compensate the memory effects as terms of their non linearity. A brief description
of some characterization techniques will be explained. These nonlinear modeling
techniques can be applied to the design of successful predistortion algorithms.
The overall structure of a linearized transmitter using Memory Polynomial Digital
Predistortion (MP DPD) architecture is represented to obtain both linearity and
efficiency of the nonlinear PAs. The results are obtained by simulations through
MATLAB. An open loop test bench is set up by using ZVE-8G+ power amplifier
and Agilent equipment such as Agilent vector signal generator (VSG)EXG-D series
and Agilent vector signal analyzer (VSA) PXI series in order to generate LTE
down-link signal with 5 MHz bandwidth. Then, the test bench's output signal is
given in arbitrary waveform format (I/Q) to the MATLAB software as the input.In conclusion, MP DPD is resulted in as improvement between 15 to 20 dB in
the adjacent channel power ratio (ACPR). Therefore, the characteristics of the
realized amplifiers are measured to satisfy the Error Vector Magnitude (EVM)
and desired power spectral density (PSD) is plotted as requirements for Wideband
Code Division Multiple Access (WiMAX) base stations and LTE down-link
signal. Effect of some elements like: number of iterations, input power back-of
(IBO) points, the memory effect modelling ration (MEMR) matric for different
PAs with memory effects and memory-less respectively, on the performance of
predistorter, are investigated. |
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