Digital filters

Claim 2

A digital filter for generating processed output samples of a signal Y from input terms representing sequential values of samples of an input signal X, said filter comprising: a. means for algebraically and cyclically adding sequences of predefined coefficients to the sequence of terms representing the latest values of samples of the data to be filtered; b. a memory storing the squares of the values of all possible sums resulting from the operations performed by said adding means; c. addressing means for said memory to receive one of said sums from said adding means and to control readout from said memory of the corresponding square value; and d. means for accumulating said square values fetched from said memory during each of said sequences to provide a corresponding sample of a filtered output signal Y.

Claim 3

A digital filter of the type wherein a sample Yi of a desired filtered output signal at instant i is generated by the accumulation of the products of the values of samples xi-k of an input signal x and corresponding coefficients ak, said filter characterized in that it includes: a. a first means for generating the term Ui defined by the expression

Claim 4

A digital filter of the type wherein a sample Yi of a desired filtered output signal at instant i is generated by the accumulation of the products of the values of samples xi-k of an input signal x and corresponding coefficients ak, said filter characterized in that it includes: a. a first means for generating the term Ui defined by the expression

Claim 5

A digital filter of the type wherein the value of a sample Yi of the desired filtered output signal at instant i is obtained by accumulating the values of samples of an input signal x weighted by corresponding coefficient values, characterized in that said filter includes: a. a storage device to provide sequences of coefficient values; b. a first means for forming addresses by adding the filter coefficients to corresponding samples of the signal x to be filtered; c. a memory having at each storage address, a value representing the square of the memory address; d. a second means for addressing said memory storing the squares of the addresses, using the address values provided by said first means; e. a register means for accumulating the values thus fetched from said memory; f. a third means for forming a second set of storage addresses by subtracting the filter coefficients from corresponding ones of said consecutive samples of the signal x to be filtered; g. a second squares memory; h. a fourth means for addressing said second squares memory, using the values supplied by said third means; i. a fifth means for subtracting the values read out from said second squares memory as a result of the addressing performed by said fourth means from the accumulation performed by said second means.

Claim 6

A digital filter of the type wherein the value of a sample Yi of the desired filtered output signal at instant i is obtained by accumulating the values of samples of an input signal x weighted by corresponding coefficient values, characterized in that said filter includes: a. a storage device to provide sequences of coefficient values; b. a first means for forming addresses by adding the filter coefficients to corresponding samples of the signal x to be filtered; c. a memory having at each storage address, a value representing the square of the memory address; d. a second means for addressing said memory storing the squares of the addresses, using the address values provided by said first means; e. a register means for accumulating the values thus fetched from said memory; f. a third means for forming a second set of storage addresses by subtracting the filter coefficients from corresponding ones of said consecutive samples of the signal x to be filtered; g. a second squares memory; h. a fourth means for addressing said second squares memory, using the values supplied by said third means; i. a fifth means for subtracting the values read out from said second squares memory as a result of the addressing performed by said fourth means from the accumulation performed by said second means.