Patent ID: 7046723

Claim:
A digital filter comprising: a) delay means for delaying input sample data by predetermined delay periods to generate delayed input sample data; b) look-up table means for pre-storing weighted sample data corresponding to multiplications of input sample data with predetermined filter coefficients, wherein said input sample data and said delayed input sample data are used for addressing said look-up table means; and c) bit shifting means for generating other weighted sample data corresponding to other multiplications of input sample data with predetermined filter coefficients by performing a bit shifting operation using said pre-stored weighted coefficients, wherein the values of said other weighted sample data correspond to the values of said pre-stored weighted sample data multiplied by two or a power of two, wherein said other weighted sample data correspond to input sample data the value of which can be obtained by multiplying another input sample data by a factor equal to two or a power of two, and are generated by using a corresponding one of said pre-stored weighted sample data relating to said other input sample data and performing a corresponding bit shifting operation in accordance with said multiplication factor, and wherein said pre-stored weighted sample data are stored in look-up tables each corresponding to one filter coefficient, and wherein said digital filter comprises an index table for addressing said another sample data, and a zero pad table indicating the number of bit shifting operations to be performed using said corresponding one of said pre-stored weighted sample data relating to said other sample data.