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US 5,353,309 AGranted
ISDN transmitter
AssigneeAT&T Bell Laboratories
InventorsOscar E. Agazzi, Steven R. Norsworthy
Life of this patent
Estimating the term…
Abstract
A transmitter suitable for ISDN use feeds the 2B1Q transmit signals directly into a sigma-delta modulator. The input word is two or three bits and the datapath within the sigma-delta modulator need be only six bits wide. The sigma-delta modulator has sample-hold means which has some filtering effect. The additional filtering requirements are met with an analog filter. No digital interpolation filter is required.
Claims9
A transmitter comprising:
- an encoder for receiving an incoming digital data stream at a first clock rate and converting it into digital PCM levels at a second clock rate;
- a transmit clock which is connected to the encoder and comprises means for adjusting the phase of the data stream;
- a sigma-delta modulator which receives the data stream from the encoder and operates at a third clock rate;
- and
- a filter, said filter comprising means for sample-hold at a third-clock rate connected to said modulator, and an analog filter which receives the output from said sigma-delta modulator.
2 more elements
A device comprising:
- means for receiving a digital data stream and encoding it into digital pulse code modulated levels;
- means for adjusting the phase of said digital pulse code modulated levels;
- sample-hold means for receiving said phase-adjusted digital pulse code modulated levels;
- sigma-delta modulator for receiving the signal from said sample-hold means and encoding said signal into a 1-bit data stream;
- and
- a low pass filter for said 1-bit data stream.
3 more elements
Dependencies are inferred from the claim text.