  In low-intermediate-frequency (low-IF) receivers, I/Q imbalance (IQI) causes
interference on the desired signal from the blocker signal transmitted over the
image frequencies. Conventional approaches for data-aided IQI estimation in
zero-IF receivers are not applicable to low-IF receivers. In zero-IF receivers,
IQI induces self-interference where the pilots of the image interference are
completely identified. However, in low IF receivers, the image interference
originates from a foreign signal whose training sequence timing and structure
are neither known nor synchronized with the desired signal. We develop a
data-aided subspace method for the estimation of IQI parameters in low-IF
receivers in the presence of unknown fading channel. Our approach does not
require the knowledge of the interference statistics, channel model nor noise
statistics. Simulation results demonstrate the superiority of our approach over
other blind IQI compensation approaches.
