Blind Compensation of I/Q Filter Imbalance in the LTE Downlink

Conference: European Wireless 2011 - Sustainable Wireless Technologies
04/27/2011 - 04/29/2011 at Vienna, Austria

Proceedings: European Wireless 2011

Pages: 7Language: englishTyp: PDF

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Petit, Michael; Haselmayr, Werner; Springer, Andreas (Institute for Communications Engineering and RF-Systems, Johannes Kepler University of Linz, Altenbergerstr. 69, 4040 Linz, Austria)

In direct conversion receivers differences of the analog components in the I- and the Q-branch lead to I/Q mismatch. Digital signal processing can be used to reduce the specification for the RF circuitry. In this paper we focus on the compensation of frequency dependent I/Q mismatch due to different cut-off frequencies of the lowpass filters. This mismatch, which is an issue due to the wide bandwidth used e. g. in LTE systems, is compensated with a second order statistic-based approach. The blind adaptive algorithm recovers a property of complex signals, called properness which is disturbed by the I/Q mismatch. The algorithm achieves a very good performance even with a mismatched upconversion stage. It is able to compensate cut-off differences higher than 10% and is independent of special pilot structures and Rayleigh fading channels.