Multiplex communications – Wide area network – Packet switching
Patent
1995-07-31
1996-10-01
Chin, Wellington
Multiplex communications
Wide area network
Packet switching
375344, H04L 2734
Patent
active
055616658
ABSTRACT:
An automatic frequency compensation apparatus comprises: a frequency offset prediction portion for predicting a frequency offset of an oscillation signal used for receiving a TDM digital modulation signal from the center frequency of the TDM digital modulation signal using a quadrature baseband signal derived from the TDM digital modulation signal, a vector correlation portion detecting a correlation between the quadrature baseband signal and a predetermined signal, the frequency offset prediction portion predicting when the correlation exceeds a reference value, and a frequency offset compensation portion effects a frequency offset compensation to the quadrature baseband. A convergent coefficient may be decreased with the number of events that the correlation exceeds the reference value. An equalizer may be further provided after the frequency offset compensation portion and the prediction is made using the output of the equalizer. The prediction is effected during the training period or during the training period when the correlation exceeds the reference value. The correlation may be detected using the output of the equalizer and a signal obtained by Judging or digitizing the output of the equalizer.
REFERENCES:
patent: 5255290 (1993-10-01), Anvari
patent: 5282228 (1994-01-01), Scott et al.
patent: 5343499 (1994-08-01), Jasper et al.
patent: 5412695 (1995-05-01), Murata
patent: 5440587 (1995-08-01), Ishikawa et al.
Matsuoka Akihiko
Ohnishi Hiroshi
Orihashi Masayuki
Takahashi Ken'ichi
Chin Wellington
Matsushita Electric - Industrial Co., Ltd.
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