Statistics-Based Approach for Blind Post-Compensation of Modulator's Imperfections and Power Amplifier Nonlinearity

Power amplifier (PA) nonlinearity and in-phase and quadrature-phase (I/Q) imbalance are major concerns for wireless transmitters. In this paper, we present a new closed-form expression for the probability density function (PDF) of I and Q components in the presence of transmitter's impairments...

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Bibliographic Details
Published in:IEEE transactions on circuits and systems. I, Regular papers Regular papers, 2019-03, Vol.66 (3), p.1063-1075
Main Authors: Aziz, Mohsin, Amiri, Mehdi Vejdani, Helaoui, Mohamed, Ghannouchi, Fadhel M.
Format: Article
Language:English
Subjects:
<italic xmlns:ali="http://www.niso.org/schemas/ali/1.0/" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">I/Q imbalance
Closed form solutions
Compensation
Cumulative distribution function
Divergence
Economic models
Exact solutions
Jacobian matrices
KL divergence
Mathematical analysis
Maximum likelihood estimation
Modulation
Nonlinearity
Parameter estimation
Peak to average power ratio
power amplifier
Power amplifiers
Probability density function
Probability density functions
Receivers
Transmitters
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Summary:Power amplifier (PA) nonlinearity and in-phase and quadrature-phase (I/Q) imbalance are major concerns for wireless transmitters. In this paper, we present a new closed-form expression for the probability density function (PDF) of I and Q components in the presence of transmitter's impairments and propose a blind post-compensation approach for the mitigation of these impairments. These impairments include static PA nonlinearity and frequency-independent I/Q imbalance. The accuracy of the analytical PDF is evaluated using Kullback-Leibler divergence and Hellinger square distance. Simulation results show a reasonable correspondence between the derived PDF and non-parametric kernel density estimation-based PDF. After a closed-form PDF is obtained, higher order statistics-based method is used to estimate PA nonlinearity in the presence of I/Q impairments. Finally, a maximum-likelihood estimation of I/Q imbalance parameters is obtained using the analytical PDF. Simulation results show a normalized mean-squared error (NMSE) of around -40 dB and an adjacent channel power ratio of around -53 dBc, along with an error vector magnitude (EVM) of around 1%, for a 3-MHz local thermal equilibrium signal. Using laboratory measurements, an NMSE of around -35 dB and an EVM of 1.5% are achieved.
ISSN:1549-8328
1558-0806
DOI:10.1109/TCSI.2018.2877940