Joint Phase Recovery for XPIC System Exploiting Adaptive Kalman Filtering

The phase recovery scheme of a cross-polar interference cancellation (XPIC) system is considered here, assuming two completely independent RF transceiver chains for the two different polarizations. A novel Kalman-based algorithm is proposed to jointly recover the phase of both the main polarization signal and the interfering one, at each single receiver of an XPIC system. The time evolution of the received phases and frequencies is represented by using both a new four-state model and a simplified two-state implementation. Simulations are conducted considering a typical backhaul link and the results prove the effectiveness of the proposed solution, compared to a common phase-locked loop (PLL) approach. Unlike the PLL scheme, the proposed Kalman-based algorithm directly adapts its parameters according to the different channel conditions, i.e., the signal-to-noise ratio per bit ($E_b/N_0$) and the the cross-polarization discrimination (XPD).