Telecommunications – Receiver or analog modulated signal frequency converter – Signal selection based on frequency
Patent
1998-06-09
2000-11-14
Nguyen, Lee
Telecommunications
Receiver or analog modulated signal frequency converter
Signal selection based on frequency
4551921, 4551821, 4551822, 455208, 455214, 375344, 331175, 331176, H04B 126, H04L 2722, H04L 2714
Patent
active
061481874
ABSTRACT:
The invention provides an automatic frequency control (AFC) method and circuit for use with a receiver by which deterioration of the reception characteristic of the receiver due to frequency error of the reference oscillator (e.g. a VCO) of a quasi-synchronous detection circuit arising from initial deviation, aging, or temperature characteristics is suppressed. During operation of the receiver, only when frame synchronization is established, the set value that the frequency control circuit determines for the VCO is periodically stored into a non-volatile memory together with current ambient temperature information of the VCO. When information that power supply has been turned on or that a changing over of the reception channel has occurred is received from an apparatus control processor, one of the stored values of the non-volatile memory is read back into the frequency control circuit in response to the current ambient temperature of the VCO by a control circuit and switches, and is used as the initial set value for the VCO. This decreases the time required for convergence of AFC and improves the synchronization acquisition characteristic of the receiver.
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Japanese Office Action issued Nov. 30, 1999 in a related application and English translation of relevant portions.
NEC Corporation
Nguyen Lee
Nguyen Simon
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