Pulse or digital communications – Systems using alternating or pulsating current – Plural channels for transmission of a single pulse train
Reexamination Certificate
2006-04-25
2006-04-25
Vo, Don N. (Department: 2631)
Pulse or digital communications
Systems using alternating or pulsating current
Plural channels for transmission of a single pulse train
C375S326000
Reexamination Certificate
active
07035339
ABSTRACT:
A carrier recovery apparatus for digital Quadrature Amplitude Modulation (QAM) receivers is disclosed. The carrier recovery apparatus includes a phase detector, a lock controller, a frequency locker and a phase loop filter, and provide phase/frequency error information for a numerically controlled oscillator (NCO) to generate recovered carrier frequency. The phase detector detects the symbol energy information and the phase error information of the extracted symbols from the I/Q extractor. The lock controller monitors the symbol energy from the phase detector, separates the extracted symbols into two groups: valid and non-valid, and outputs the control flag of valid symbols into both the frequency locker and the phase loop filter. To achieve a wide range acquisition and a good tracking performance, the lock controller controls the operation of the frequency locker and the phase loop filter in three operations. The detected frequency offset from the frequency locker and the phase offset detected from the phase loop filter are both fed into the NCO to recover the carrier offset.
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Lowe Hauptman & Berner LLP
Silicon Integrated Systems Corp.
Vo Don N.
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