Application of memory-based filtering to passband spectral shaping of a high-speed transmitted data stream.

Precise spectral shaping of transmitted passband signals is of fundamental importance in advanced data communication systems, where it finds application ranging from voiceband modems to megabaud digital radio. In this study, the authors extend earlier work in memory-based digital filtering of baseband signals to include passband spectral shaping of a high-speed transmitted data stream. Included are a presentation of the fundamental concepts, described with the aid of functional circuit descriptions and experimental data, the latter for a 4-level, 12.68-Mb/s half-Nyquist passband data signal with a 6.34-MHz IF. Extension of the digital filter architecture to QAM signals, with predistortion for linear passband dispersion, is also outlined.