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US 4,905,255 AGranted
Decision directed gain control
AssigneesAmerican Telephone and Telegraph Company, AT&T Bell Laboratories
InventorFarajollah Aalaei
Life of this patent
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Abstract
In a receiver for receiving and decoding a baseband multilevel signal into a digital data signal, and A/D converter produces in addition to the decoded data bits a "soft" bit, which inherently indicates the error polarity of the baseband signal. The soft bits are binary added to the most significant data bits to produce a sum bit. The sum bits are integrated, and the integral is used in a feedback loop to control the baseband signal amplitiude.
Claims1
In a receiver having decoding means for decoding a baseband multilevel signal into a digital data signal,
- said decoding means comprising quantizing means for quantizing said multilevel signal into discrete amplitude ranges and producing in response to each discrete amplitude range a unique combination of bits including a plurality of data bits in descending order of significance to form said data signal and a less significant soft bit,
- an arrangement for automatically controlling the amplitude of said multilevel signal comprising:
- an EXCLUSIVE-OR gate connected to said quantizing means and having a first output for producing a modulo-two sum of said soft bit and said most significant bit and a second output for producing the complement of said sum;
- an integrating differential amplifier having an output, an inverting input connected to said first EXCLUSIVE-OR gate output and a non-inverting input connected to said second EXCLUSVIE-OR gate output;
- resistance means connected in series in the path of said multilevel signal;
- and
- a transistor having its gate electrode connected to the output of said differential amplifier and its source-drain path connected from a point on said multilevel signal path between said resistance means and said quantizing means to ground.
4 more elements
Dependencies are inferred from the claim text.