On the lower I/Q imbalance sensitivity using real-valued feedback of digital predistortion

The adaptive digital predistortion is currently widely used to compensate for the nonlinearities. Usually the observing (feedback) path of the predistorter is required to be very accurate. That means it is compensated for any radio frequency front-end imperfections. In this paper we demonstrate that recently proposed (real-valued) digital predistortion algorithm employing only one of the signals in the quadrature pair implies the reduced sensitivity of the predistorter adaptation to the I/Q modulator imbalance in the feedback path. The lower sensitivity is demonstrated using both simulation as well as by an experiment conducted using the mm-Wave setup with integrated direct-conversion transceiver with important imbalances in both transmitting (Tx) as well as in receiving (Rx) path.