Carrier recovery processor for a QAM television signal

In a television signal receiver including a signal processing path for processing a television signal containing a carrier quadrature amplitude modulated (QAM) with symbols exhibiting a given symbol period and mapped into prescribed locations of a grid-like constellation, apparatus comprising:

• means for generating a reference signal nominally at the frequency of said carrier;
• input means responsive to said modulated carrier and to said reference signal for producing a processed modulated carrier;
• means for generating a control signal as a function of an offset exhibited by a constellation associated with said processed carrier relative to a constellation associated with said television signal;
• and
• means for coupling said control signal to said signal processing path for reducing said offset;
• wherein
• said means for generating said control signal is a time multiplexed processor with plural operating modes providing a product-type output signal in at least one of said plural operating modes representative of said offset, said multiplexed processor being responsive to a first signal containing a constellation of symbols at received locations, and to a second signal containing a constellation of symbols at expected locations, said output signal of said multiplexed means representing a difference between said received and expected locations.

In a television signal receiver including a signal processing path for processing a television signal containing a carrier quadrature amplitude modulated (QAM) with symbols exhibiting a given symbol period and mapped into prescribed locations of a grid-like constellation, apparatus comprising:

• means for generating a reference signal nominally at the frequency of said carrier;
• input means responsive to said modulated carrier and to said reference signal for producing a processed modulated carrier;
• means for generating a control signal as a function of an offset exhibited by a constellation associated with said processed carrier relative to a constellation associated with said television signal;
• and
• means for coupling said control signal to said signal processing path for reducing said offset;
• wherein
• said means for generating said control signal is a time multiplexed processor with plural operating modes providing a product-type output signal in at least one of said plural operating modes representative of said offset;
• and
• said multiplexed processor comprises a signal multiplier which is multiplexed with latch means to successively perform multiplying and accumulating functions.

In a television signal receiver including a signal processing path for processing a television signal containing a carrier quadrature amplitude modulated (QAM) with symbols exhibiting a given symbol period and mapped into prescribed locations of a grid-like constellation, apparatus comprising:

• means for generating a reference signal nominally at the frequency of said carrier but subject to exhibiting a phase or frequency offset with respect to said carrier;
• input means responsive to said modulated carrier and to said reference signal for producing a processed modulated carrier;
• means for generating a control signal as a function of said offset, said means for generating said control signal including a phase locked loop comprising multiplier means providing an output signal as a function of said offset in response to a first signal with symbols at received locations and to a second signal with symbols at expected locations;
• means for providing timing signals to said phase locked loop for causing said phase locked loop including said multiplier means to exhibit time-multiplexed operation;
• and
• means for coupling said control signal to said signal processing path for reducing said offset.

In a television signal receiver including a signal processing path for processing a television signal containing a carrier quadrature amplitude modulated (QAM) with symbols exhibiting a given symbol period and mapped into prescribed locations of a grid-like constellation, apparatus comprising:

• means for generating a reference signal nominally at the frequency of said carrier but subject to exhibiting a phase of frequency offset with respect to said carrier;
• input means responsive to said modulated carrier and to said reference signal for producing a processed modulated carrier;
• means for generating a control signal as a function of said offset, said generating means including a second order phase locked loop comprising multiplier means providing an output signal as a function of said offset in response to a first signal with symbols at received locations and to a second signal with symbols at expected locations;
• means for providing timing signal to said phase locked loop for causing said phase locked loop including said multiplier means to exhibit time-multiplexed operation;
• and
• means for coupling said control signal to said signal processing path for reducing said offset, wherein said phase locked loop includes
• means responsive to said processed modulated carrier for selecting said symbols, said selecting means exhibiting a first signal gain factor and including memory means for generating said second signal with said symbols at expected locations.