Digital detector
First Claim
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1. A digital detector to convert an audio frequency signal into a digital signal, characterized in that the detector comprises:
- an Analogue/Digital (A/D) converter (7), for producing a first binary word (Wo) corresponding to the offset voltage of the detector, and a second binary word (Ws) corresponding to each detected signal;
offset voltage removal means (8), in which the first binary word (Wo) corresponding to the offset voltage of the detector is subtracted from each second binary word (Ws) corresponding to each received signal to provide a plurality of third binary words (Wss) representing modified signal symbols corresponding to each received signal;
means for comparing each third binary word (Wss) with a set of predetermined decision levels to determine an output symbol; and
means for updating the set of predetermined decision levels responsive to changes in the received audio frequency signals as represented in changes in the third binary words (Wss).
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Abstract
The invention comprises a digital detector used in a paging system. This detector has reference levels, against which the received signal is compared with a digital comparator (11). The reference levels can be changed with an updating logic (12), if changes are observed in the levels of the received signals. The detector may also compensate for differences between individual FM detectors.
10 Citations
12 Claims
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1. A digital detector to convert an audio frequency signal into a digital signal, characterized in that the detector comprises:
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an Analogue/Digital (A/D) converter (7), for producing a first binary word (Wo) corresponding to the offset voltage of the detector, and a second binary word (Ws) corresponding to each detected signal; offset voltage removal means (8), in which the first binary word (Wo) corresponding to the offset voltage of the detector is subtracted from each second binary word (Ws) corresponding to each received signal to provide a plurality of third binary words (Wss) representing modified signal symbols corresponding to each received signal; means for comparing each third binary word (Wss) with a set of predetermined decision levels to determine an output symbol; and means for updating the set of predetermined decision levels responsive to changes in the received audio frequency signals as represented in changes in the third binary words (Wss). - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for operating a digital detector for converting an audio frequency signal into a digital signal, comprising the steps of:
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producing a first binary word (Wo) corresponding to an offset voltage of the detector and a second binary word (Ws) corresponding to each detected signal; subtracting the first binary word (Wo) from each second binary word (Ws) to provide a plurality of third binary words (Wss) representing modified signal symbols corresponding to each received signal; comparing each third binary word (Wss) with a set of predetermined decision levels to determine an output symbol; and updating the set of predetermined decision levels in response to a change in the received audio frequency signals as represented by a change in the third binary words (Wss). - View Dependent Claims (9, 10, 11, 12)
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Specification