Jointly Adaptive Equalization and Carrier Recovery in Two-Dimensional Digital Communication Systems

In recent years, a number of double-sideband suppressed-carrier linear-modulation techniques have seen increasing application to the efficient transmission of digital d a t a over band-limited channels. Twodimensional modulation may be an appropriate designation for these techniques, since they call for coding the transmitted d a t a as twodimensional d a t a symbols and transmitting the two components by amplitude-modulating two quadrature carrier waves. Phase-shift keying (PSK) and quadrature amplitude modulation (QAM, sometimes termed QASK), illustrated in Fig. 1, are familar examples. Other two-dimensional modulation examples, characterized by their signal constellations (discrete sets of two-dimensional d a t a symbols), have been extensively studied. 1 - 3 This paper presents a unified t r e a t m e n t of adaptive equalization, carrier recovery, and demodulation for two-dimensional-modulated d a t a communication systems. Most previous studies of QAM and PSK systems have treated these receiver functions separately. 4 - 8 Kobayashi 317