Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Research Article New Adaptive Method for IQ Imbalance Compensation of Quadrature Modulators in Predistortion Systems | Hindawi Publishing Corporation EURASIP Journal on Advances in Signal Processing Volume 2009 Article ID 181285 10 pages doi 2009 181285 Research Article New Adaptive Method for IQ Imbalance Compensation of Quadrature Modulators in Predistortion Systems Hassan Zareian and Vahid Tabataba Vakili Electrical Engineering Department Iran University of Science and Technology IUST Tehran 16846-13114 Iran Correspondence should be addressed to Hassan Zareian zareian@ Received 7 February 2009 Revised 13 May 2009 Accepted 23 June 2009 Recommended by George Tombras Imperfections in quadrature modulators QMs such as inphase and quadrature IQ imbalance can severely impact the performance of power amplifier PA linearization systems in particular in adaptive digital predistorters PDs . In this paper we first analyze the effect of IQ imbalance on the performance of a memory orthogonal polynomials predistorter MOP PD and then we propose a new adaptive algorithm to estimate and compensate the unknown IQ imbalance in QM. Unlike previous compensation techniques the proposed method was capable of online IQ imbalance compensation with faster convergence and no special calibration or training signals were needed. The effectiveness of the proposed IQ imbalance compensator was validated by simulations. The results clearly show the performance of the MOP PD to be enhanced significantly by adding the proposed IQ imbalance compensator. Copyright 2009 H. Zareian and V. T. Vakili. This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited. 1. Introduction High data rate wireless communications systems use spectrally efficient modulations such as the orthogonal frequency division multiplexing OFDM . These systems are highly sensitive to the nonlinear distortion introduced by the power amplifier PA due to its nonconstant envelope .