Godkända
Kompensering av IQ-obalans: Blinda och pilotbaserade algoritmer, med olika modeller för IQ-obalans
Shireen Al-majmaie (2011)
Start
2013-05-06
Presentation
2014-07-31 13:15
Plats:
E:2311
Avslutat:
2014-08-05
Examensrapport:
Sammanfattning
Today, wireless communication systems try to cope with the high demands of the different applications that require more and more throughput. This trend result in developing different technologies in order to improve both the transmitter and the receiver side of the communication link. On the other hand, in order to reduce the price of the communication handsets, more cheap analogue components with sub-optimal front-ends are used. To reduce the effect of these hardware impairments, more signal processing is required. One of these hardware impairments is the IQ imbalance which result in distorting the constellation of the received signal in one or both of the I and the Q branches. The effect of the IQ imbalance on degrading the performance of the system becomes more pronounced when higher order modulation, for example 64 QAM, is used, where the constellation is more sensitive to symbol rotation and interference between the I and the Q branches. In this thesis work, the performance of two IQ imbalance compensation algorithms are studied. One of them is a blind algorithm and the other one is a pilot-based algorithm. We also examine the performance of these algorithms under two IQ imbalance models: the Double Branch IQ imbalance Model (DBIQM), and the Single Branch IQ imbalance Model (SBIQM). It was found that the two IQ imbalance models are related via a rotation and a scaling operations. It was also found that, since both algorithms implicitly use the SBIQM, their performance degrades significantly if the actual IQ imbalance follows the DBIQM. However, a simple modification is suggested to these algorithms that improves their performance when the IQ imbalance follow the DBIQM. In all case, evaluating the performance is performed based on the bit-error-rate (BER), and the signal-to-distortion- ratio (SDR).
Handledare: Ghassan Dahman (EIT)
Examinator: Ove Edfors (EIT)