Pulse or digital communications – Systems using alternating or pulsating current – Plural channels for transmission of a single pulse train
Reexamination Certificate
2005-10-11
2005-10-11
Chin, Stephen (Department: 2634)
Pulse or digital communications
Systems using alternating or pulsating current
Plural channels for transmission of a single pulse train
C375S295000, C375S222000
Reexamination Certificate
active
06954505
ABSTRACT:
A transceiver (100) such as used in Discrete Multitone (DMT) modulation of digital signals for communication, such as in a DSL modem communications system, is described. The transceiver (100) includes a function (119) by way of which unloaded subchannels are encoded with a clip prevention signal. The clip prevention signal is derived to avoid clipping by an amplifier (18) after modulation into the time domain, upsampling, and filtering. The effects of the upsampling and filtering are considered in deriving the clip prevention signal, by considering the upsampling and filtering as a polyphase combination, and using the filter response for each phase. Frequency domain and time domain update alternatives are disclosed.
REFERENCES:
patent: 6240141 (2001-05-01), Long
patent: 6366555 (2002-04-01), Gatherer et al.
patent: 0 957 615 (1999-11-01), None
Gatherer, et al., “Controlling Clipping Probability in DMT Transmission”,Proceedings of the Asilomar Conference on Signals, Systems, and Computers(IEEE, 1997), pp. 578-584.
Gatherer Alan
Polley Michael O.
Redfern Arthur J.
Brady III W. James
Chin Stephen
Joseph Jaison
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
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