Pulse or digital communications – Receivers – Interference or noise reduction
Reexamination Certificate
1996-07-01
2001-04-03
Chin, Stephen (Department: 2734)
Pulse or digital communications
Receivers
Interference or noise reduction
C455S218000, C455S229000, C375S217000
Reexamination Certificate
active
06212245
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a communication apparatus which controls communications in accordance with the reception state.
A communication apparatus such as a cordless telephone apparatus comprises a filter for removing noise.
However, if the received signal is filtered even when the reception state is good, i.e., is free from noise, the sound quality is impaired.
Conventionally, discrimination of the presence/absence of a carrier is attained by circuit design. More specifically, a circuit for outputting a HIGH- or LOW-level voltage indicating whether or not the electric intensity is higher than a prescribed value is designed, and the output from this circuit is monitored by a CPU, thereby discriminating the presence/absence of the carrier.
However, in this prior art, the prescribed value varies due to performance variations of parts. For example, even when the presence/absence of the carrier is to be discriminated using a prescribed value of 1.3 &mgr;V, the prescribed value varies in practice, and it is difficult to comply with the pertinent regulation.
When a plurality of carrier level prescribed values are used for controlling the circuit, carrier level discrimination circuits corresponding in number to the prescribed values must be prepared, resulting in high cost.
SUMMARY OF THE INVENTION
It is an object of the present invention to improve the quality of a communication signal.
It is another object of the present invention to improve noise removal.
It is still another object of the present invention to reduce the margin for absorbing variations in performance of parts.
It is still another object of the present invention to accurately discriminate the presence/absence of a carrier.
It is still another object of the present invention to provide an arrangement for improving the quality of a communication signal.
Other objects of the present invention will become apparent from the following description of the embodiments taken in conjunction with the accompanying drawings.
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Canon Kabushiki Kaisha
Chin Stephen
Ghayour Mohammad
Morgan & Finnegan , LLP
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