System for varying the dynamic range of coefficients in a digital filter

A method of filtering input data using a digital filter comprised of a plurality of filter cells, each of the plurality of filter cells for generating a filter cell output based on input data and a coefficient, the method comprising the steps of:

• a coefficient determining step for determining a coefficient of each of the plurality of filter cells;
• a coefficient adjusting step for adjusting the coefficient of each filter cell in accordance with a gain that is used by each of the plurality of filter cells;
• a multiplying step for multiplying input data in each filter cell by an adjusted coefficient so as to generate a filter cell output for each filter cell;
• an adding step for adding filter cell outputs from each of the plurality of filter cells so as to generate a filter output;
• and
• an output adjusting step for adjusting the filter output in accordance with an inverse of the gain used to adjust the coefficients of the plurality of filter cells.

A digital filter comprising:

• a first plurality of filter cells, each of the first plurality of filter cells including circuitry to determine a coefficient for the filter cell, to adjust the coefficient in accordance with a first gain that is used by each of the first plurality of filter cells, and to multiply input data by the adjusted coefficient in order to generate a first filter cell output;
• a first adder circuit which generates a first output by adding first filter cell outputs from each of the first plurality of filter cells;
• a first inverse gain circuit which generates a first adjusted output by adjusting the first output in accordance with an inverse of the first gain used to adjust the coefficients of the first plurality of filter cells;
• a second plurality of filter cells, each of the second plurality of filter cells including circuitry to determine a coefficient for the filter cell, to adjust the coefficient in accordance with a second gain that is used by each of the second plurality of filter cells, and to multiply input data by the adjusted coefficient in order to generate a second filter cell output;
• a second adder circuit which generates a second output by adding second filter cell outputs from each of the second plurality of filter cells;
• a second inverse gain circuit which generates a second adjusted output by adjusting the second output in accordance with an inverse of the second gain used to adjust the coefficients of the second plurality of filter cells;
• and
• a third adder circuit which adds the first adjusted output and the second adjusted output in order to generate a filter output for the digital filter.

A digital filter comprising:

• a plurality of filter cells, each of the plurality of filter cells including circuitry to determine a plurality of coefficients for the filter cell, to adjust each of the plurality of coefficients in accordance with a gain that is used by each of the plurality of filter cells, and to multiply a corresponding data value input to the filter cell by a corresponding adjusted coefficient in order to generate to generate a filter cell output;
• an adder circuit which generates a filter output by adding filter cell outputs from each of the plurality of filter cells;
• and
• an inverse gain circuit which adjusts the filter output in accordance with an inverse of the gain used to adjust the coefficients of the plurality of filter cells.