Pulse or digital communications – Transmitters – Quadrature amplitude modulation
Reexamination Certificate
2006-06-27
2006-06-27
Fan, Chieh M. (Department: 2634)
Pulse or digital communications
Transmitters
Quadrature amplitude modulation
C375S261000, C375S296000, C375S354000, C370S206000, C332S103000
Reexamination Certificate
active
07068730
ABSTRACT:
Wideband, direct-to-RF multi channel QAM modulation is described whereby IFFT processing is employed to modulate a plurality of encoded symbol streams in parallel onto a like plurality of uniformly spaced carriers. A high-frequency master clock and high-performance, high-frequency D/A converters are employed. The IFFT modulation process yields a multi-channel multiplex at an intermediate “baseband” frequency. The multi-channel multiplex is then synchronously converted to analog form and synchronously frequency shifted upward by one-half the master clock frequency using a quadrature doubly-balanced mixing scheme. The resultant multi-channel encoded multiplex occupies a frequency band centered around one half the master clock frequency. Multi-rate techniques can be employed to yield high-speed digital processing from digital logic incapable of operating directly at the master clock frequency.
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Fan Chieh M.
Lipsitz & McAllister LLC
RGB Networks, Inc.
Wang Ted M.
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