Analog signals encoded with quadrature amplitude modulation (QAM) pass through
a coaxial cable at a particular baud rate. These signals have a carrier frequency
individual to the TV station being received. They are mixed with signals from a
variable frequency oscillator to produce signals at a particular intermediate frequency
(IF). An analog-digital converter (ADC) converts the IF signals to corresponding
digital signals which are demodulated to produce two digital signals having a quadrature
phase relationship. After being filtered and derotated, the digital signals pass
to a symmetrical equalizer including a feed forward equalizer (FFE) and a decision
feedback equalizer (DFE) connected to the FFE in a feedback relationship. The DFE
may include a slicer providing amplitude approximations of increasing sensitivity
at progressive times. Additional slicers in the equalizer combine the FFE and DFE
outputs to provide the output data without any of the coaxial cable noise or distortions.
The equalizer outputs and initially the derotation outputs, and the slicer outputs,
servo (1) the oscillator frequency to obtain the IF frequency, (2) the ADC sampling
clock to obtain the digital conversion at a rate related to the particular baud
rate and (3) the derotator. The servos may have (1) first constants initially after
a change in the station selection and (2) second time constants thereafter. The
ADC gain is also servoed (1) initially in every ADC conversion and (2) subsequently
in every nth ADC conversion where n=integer1. The above recover the QAM data
without any of the coaxial cable noise or distortions.