Linear phase robust carrier recovery for QAM modems

Details Linear phase robust carrier recovery for QAM modems Linear phase robust carrier recovery for QAM modems

2005-06-07

2005-06-07

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, C375S327000, C375S350000

Reexamination Certificate

active

06904098

ABSTRACT:
In a QAM demodulator including an adaptive equalizer, a method of carrier tracking comprising the following steps is disclosed: (A) sampling a QAM signal received from a transmission channel; (B) recovering a symbol clock function from the sampled QAM signal; (C) applying the sampled QAM signal to the adaptive equalizer in order to obtain a QAM equalized signal in a Blind Equalization (BE) mode; (D) using a slicer to locate a nearest plant point for the QAM Blind equalized signal for each recovered symbol clock; (E) using a complex conjugate multiplier to obtain an instantaneous inphase component and an instantaneous quadrature component of a phase angle error signal; (F) using a linear phase detector to obtain an instantaneous phase angle error for each symbol clock; (G) averaging the instantaneous phase angle error signal by using a carrier loop filter; (H) using a complex multiplier to insert an inverse of the averaged phase angle error signal into the QAM Blind equalized signal to compensate for the carrier phase angle error; and (I) repeating the steps (D-H) to close a carrier frequency loop.

REFERENCES:
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patent: 2003/0058967 (2003-03-01), Lin et al.
Jablon, N. K., “Joint Blind Equalization, Carrier Recovery, and Timing Recovery for Hogh-Order QAM Signal Constellations” IEEE vol. 40, No. 6 Jun. 1992, pp. 1383-1389.

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