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Modeling, analysis and compensation of LO leakage and IQ-imbalance in a UMTS receiver
2001 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

In this study, we investigate the effects that imperfections in radio receivers have on the performance for a general M-PSK system and for WCDMA. A model for three common imperfections, LO leakage, gain imbalance, and quadrature phase error, was derived and implemented in simulations. The simulations for the general M-PSK system show that larger constellations are more sensitive to radio imperfections and might benefit from some kind of compensation algorithm. As for WCDMA, the simulations indicate no need for compensation since reasonable levels of imperfections rendered insignificant losses. Some different compensation algorithms for the general M-PSK model were developed and evaluated through simulations. A compensation algorithm using an internal calibration, taking place prior to the usage of the receiver, was implemented showing good performance. However, questions regarding the generation of an internal pilot sequence raised demand for an alternative approach. Therefore a compensation scheme, using pilot symbols generated by the transmitter and transmitted over the radio channel, was implemented showing promising results. In order for the latter compensation algorithm to function, the pilot symbols must be chosen to fulfill certain requirements. An additional algorithm, intended to function although these requirements are not fulfilled, was therefore developed showing good performance, but at the cost of high computational complexity. Finally, a possible algorithm for compensation in WCDMA is discussed.

Place, publisher, year, edition, pages
Keyword [en]
Technology, communications, UMTS, IQ-imbalance, LO leakage, WCDMA, quadrature demodulators, imperfections, radio, receivers, compensation
Keyword [sv]
URN: urn:nbn:se:ltu:diva-42157ISRN: LTU-EX--01/107--SELocal ID: 036b6350-7445-480b-9c34-b5cfee777205OAI: diva2:1015374
Subject / course
Student thesis, at least 30 credits
Educational program
Electrical Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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