Power amplifier linearization technique with IQ imbalance and crosstalk compensation for broadband MIMO OFDM transmitters

FERNANDO GREGORIO; JUAN COUSSEAU; STEFAN WERNER; TANELI RIIHONEN; RISTO WICHMAN

EURASIP Journal on Advances in Signal Processing

Springer-Verlag, GmbH

Año: 2011 vol. 19 p. 1 - 15

1687-6180

The design of predistortion (PD) techniques for broadband MIMO-OFDM systems rises several implementation challenges. First, the large bandwidth of the OFDM signal requires the introduction of memory effects in the predistortion model. In addition, it is usual to consider an imbalanced IQ modulator to translate the predistorted baseband signal to RF. Furthermore, the coupling effects that occur when the MIMO paths are implemented in the same reduced size chipset cannot be avoided in MIMO transceivers structures. This work proposes a MIMO-PD systemthat linearizes the PA response and compensates nonlinear crosstalk and IQ imbalance effects for each branch of the multiantenna system. Efficient recursive algorithms are presented to estimate the complete MIMO-PD coefficients.The algorithms avoid the high computational complexity in previous solutions based on least squares (LS) estimation.The performance of the proposed MIMO-PD structure is validated by simulations using a 2-transmitter antenna MIMO system. Error vector magnitude (EVM) and adjacent channel power ratio (ACPR) are evaluated showing a significant improvement compared with conventional MIMO-PD systems.