Jointly adaptive equalization and carrier recovery in two-dimensional digital communication systems

In this paper, we describe a novel receiver structure for two-dimensional-modulated, suppressed-carrier data signals. The receiver consists of a passband equalizer followed by a demodulator which compensates for frequency offset and phase jitter; the demodulator's phase angle is provided by a data-directed, carrier recovery loop, which is shown by analysis and simulation to be capable of tracking relatively high frequency phase jitter. A derivation of the receiver parameters is presented, based on a gradient algorithm for jointly optimizing the equalizer tap coefficients and the carrier phase estimate, to minimize the output mean-squared error. System performance is related to carrier phase-tracking parameters by analysis. Computer simulations confirm the feasibility of the receiver structure.