Transceiver Inphase/Quadrature Imbalance, Ellipse Fitting, and the Universal Software Radio Peripheral

Rojas, Cristian R.,1980-KTH,Reglerteknik,ACCESS Linnaeus Centre,System Identification Group (author)

QC 20111107
In this paper, we introduce a method for inphase/quadrature imbalance parameter estimation based on ellipse fitting. The performance of the method is analytically derived. In particular, it is shown that the method exhibits a small bias (which can be negligible under some standard practical conditions) and a variance slightly above the Cramer-Rao bound. The method is then applied to measurements from a contemporary BiCMOS transceiver which is used on one of the most popular daughterboards of the universal software radio peripheral. In our measurements, the phase skew varies up to 5 degrees with the baseband frequency, while the amplitude imbalance varies between 0 and 0.3 dB over carrier frequencies and across hardware units. The time variation, however, is only 0.004 dB in amplitude and 0.06 degrees in phase. This indicates that the units could either be calibrated online when there is no transmission (in a two-antenna MIMO system, one antenna could transmit a calibration signal to the other), or they could be calibrated during production, in which case a table with different carrier and baseband frequencies would be needed. However, there is no need to estimate the parameters on every burst.

Zetterberg, PerKTH,ACCESS Linnaeus Centre,Signalbehandling(Swepub:kth)u18qjdrj (author)
Händel, PeterKTH,ACCESS Linnaeus Centre,Signalbehandling(Swepub:kth)u1htctiy (author)
KTHReglerteknik (creator_code:org_t)

In:IEEE Transactions on Instrumentation and Measurement: IEEE60:11, s. 3629-36390018-94561557-9662

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