Equalization apparatus with fast coefficient updating operation

An equalization apparatus for use in a television signal receiving system, which includes an equalizing filter having a set of filter coefficients for equalizing a received television signal distorted from an original signal in a transmission channel to produce a filtered output signal, wherein the received television signal includes a plurality of data samples and the filtered output signal has a corresponding plurality of filter output data samples;

• and error signal generating means for storing a set of error values, and for generating, in response to a filtered output data sample, an error signal corresponding to said filtered output data sample;
• and updating circuit for generating, in response to the data sample and the error signals, a set of updated filter coefficients as the set of filter coefficients for the equalizer filter, characterized in that said updating circuit comprises:
• a shift register for storing and shifting the data sample to provide a set of the data samples;
• a multiplier for multiplying said error signal with the set of the data samples to provide a set of error weighted data samples;
• a scaling circuit, in response to a first control signal, for scaling down the set of error weighted data samples with a first scale value in order to generate a first set of scaled error weighted data samples and, in response to a second control signal, for scaling down the set of error weighted data samples with a second scale value to generate a second set of scaled error weighted data samples;
• adder means for adding the first or the second set of scaled error weighted data samples to a set of previous filter coefficients in order to produce said set of updated filter coefficients as an output of the updating circuit;
• FIFO buffer means for storing the set of updated filter coefficients as the set of previous filter coefficients for the adder means;
• and
• control means for generating the second control signal when the mean square error of the filtered output signal is identical to or smaller than a predetermined threshold value and for generating the first control signal when the mean squared error is greater than the predetermined threshold value.