Threshold setting device
First Claim
1. A decision threshold setting circuit which receives an input digital signal and sets one or more decision thresholds for decoding the input digital signal, the circuit including means for generating a current corresponding to a time-average level of the input digital signal and means for mirroring said current to generate the decision thresholds, whereby to adjust each decision threshold to a level corresponding to a predetermined fraction of said current.
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Abstract
An input digital signal developed by a signal source e.g. a photodiode is time-averaged and mirrored by a current mirror to generate one or more decision thresholds. The thresholds may be a set or variable fraction of the average current and track any variation in the average current. This obviates the need for limiting or AGC amplifiers that would otherwise be necessary to maintain the input signal level constant if the thresholds were fixed.
10 Citations
7 Claims
- 1. A decision threshold setting circuit which receives an input digital signal and sets one or more decision thresholds for decoding the input digital signal, the circuit including means for generating a current corresponding to a time-average level of the input digital signal and means for mirroring said current to generate the decision thresholds, whereby to adjust each decision threshold to a level corresponding to a predetermined fraction of said current.
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7. A method of setting decision thresholds comprising receiving an input digital signal, generating a current corresponding to a time-average level of the input signal and mirroring said current to generate one or more decision thresholds for decoding the input digital signal, whereby to adjust each decision threshold to a level corresponding to a predetermined fraction of said current.
Specification