Pulse or digital communications – Receivers – Automatic frequency control
Patent
1996-01-29
1998-10-06
Chin, Wellington
Pulse or digital communications
Receivers
Automatic frequency control
375375, 4551921, 4551922, H04L 2706
Patent
active
058188827
ABSTRACT:
A frequency offset cancellation apparatus which reduces the quantity of computations to cancel a frequency offset and decreases a processing time required for the computation. The frequency of a received high frequency signal is changed by frequency converting circuit 1 and local oscillator 2 to produce a base band signal, and converts it into a digital signal by A/D convertor 3. Correlation value signals obtained by despread the digitized base band signal with spread code shifted from inputted base band signal with respect to time are inputted to detecting circuit 5a to 5n. The detection signals from detection circuit 5a to 5n are combined by combining circuit 6. Frequency offset detection circuit 7 compares the output signal inputted from combining circuit 6 with a theoretical value of a known pilot signal portion whereby a frequency offset is detected. Frequency offset cancellation circuit 8 rotates the output signal from combining circuit 6 reversely based on the value of the frequency offset. Thus, the frequency offset of the output signal from combining circuit 6 is canceled by frequency offset cancellation circuit 8 so that an output signal, the frequency offset of which is canceled, is provided.
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"A Coherent Spread-Spectrum Diversity-Receiver with AFC for Multipath Fading Channels," IEEE Transactions on Communications, 42(1994) Feb./Mar./Apr., No. 2/3/4, New York, U.S., pp. 1300-1311.
Chin Wellington
NEC Corporation
Tran Congvan
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