Quadrature amplitude modulation receiver and carrier recovery method
AssigneeLG Electronics Inc.
InventorKeun Hee Ahn
Life of this patent
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Abstract
Disclosed is a quadrature amplitude modulation (QAM) receiver and a carrier recovery method which receive a signal modulated by the QAM method and recover the frequency offset and phase jitter of the carrier particularly using a weighted phase error inversely proportionate to the magnitude of the deciding signal character, as a result of which the phase jitter of the demodulated signal characters is constant in size irrespective of the magnitude of the deciding signal character. Consequently, acquisition/tracking can be rapidly achieved to minimize the frequency offset of several hundreds of KHz and the phase jitter generated from a tuner or an RF oscillator.
Claims20
A quadrature amplitude modulation (QAM) receiver, which converts a received passband signal on a specific channel to a baseband digital signal and then extracts a transmission symbol through carrier recovery, the QAM receiver comprising:
- a signal generator for multiplying the passband digital signal by a sine/cosine wave into a demodulated baseband digital signal, and generating a deciding signal character conformable to the individual signal level of the demodulated baseband digital signal;
- a first phase error measurer for calculating the phase difference between the demodulated baseband digital signal and the deciding signal character, and detecting the polarity of the phase difference to be output as a first phase error;
- a second phase error measurer for using the first phase error detected by the first phase error measurer to output a second phase error having a weighted value;
- and
- a filter and an oscillator for cumulating the received second phase error, and generating a sine/cosine wave proportionate to the cumulated phase error, the sine/cosine wave being output to the signal generator.
A carrier recovery method for a QAM receiver, which converts a received passband signal on a specific channel to a baseband digital signal and then perform a carrier recovery, the carrier recovery method comprising the steps of:
- (a) multiplying the passband digital signal by a sine/cosine wave into a demodulated baseband digital signal, and generating a deciding signal character conformable to the individual signal level of the demodulated baseband digital signal;
- (b) calculating the phase difference between the demodulated baseband digital signal and the deciding signal character, and detecting the polarity of the phase difference to be output as a first phase error;
- (c) using the first phase error as a control signal to output a second phase error having a weighted value;
- and
- (d) cumulating the received second phase error, and generating a sine/cosine wave proportionate to the cumulated phase error, the sine/cosine wave being output to the step (a).
Dependencies are inferred from the claim text.