Real Time Algorithms for Joint Phase Frequency Carrier Recovery with Correction for I/Q Imbalance in 16-QAM Receivers for Satellite Communications

The Quadrature-Amplitude-Modulation (QAM) plays an important role in the broadband satellite communications among which most of current digital satellite systems use QPSK(i.e.4QAM). And along with the increase of transmission rates, high-order QAM is promising to be the main modulation scheme in future satellite systems owing to its high spectral efficiency In this paper, we propose a novel structure of the joint frequency-phase carrier recovery loop for all-digital QAM satellite receivers. Unlike the existing methods, the initial phase offset is recovered through the utilization of a frequency recovery loop. By introducing a non-zero-mean input to the Stop-and-Go controller, the steady-state estimation variance is greatly reduced. This method is especially useful in the low SNR region.