Discrete transversal filter

Claim 1

A discrete transversal filter having a giving cut-off frequency for processing input samples x(n) and for generating output samples y(n) which occur with a predetermined output sampling frequency f s which is equal to an integral multiple of said cut-off frequency, which discrete filter has a predetermined lowpass transfer characteristic which is related to the transfer characteristic of a predetermined lowpass filter with impulse response h 1 (i), said discrete filter comprising: an input for receiving the input samples x(n); a tapped delay line for storing and producing N input samples x(n) wherein the delay time of the delay line situated between each two successive taps is equal to 1/f s ; first storage means for storing and producing filter coefficients h 1 (i); first multiplier means for multiplying each of the input samples produced at the said taps with a corresponding filter coefficient for generating modified input samples z(n,i) = h 1 (i)·x(n-i); first adder means; first means for coupling the input circuit of the first adder means to the output circuit of the first multiplying means; the first coupling means comprising: second adder means which are coupled to said first multiplying means for generating sum values P(n,r) which are each related to the modified input samples z(n,i) according to the expression ##EQU7## where r = 0, 1, 2 . . . , ##EQU8## second multiplying means; second coupling means for coupling the output circuit of the second adder means to the input circuit of the second multiplying means; means for producing a first, a second and a third set of coefficients {a(1,r)}, {a(2,r)}, {a(3,r)}, of which first set of coefficients {a(1,r)}, the elements a(1,r) are given by a(1,r) = 1, of which second set of coefficients {a(2,r)} the elements a(2,r) are given by a(2,r) = cos(2πrf g /f s ), of which third set of coefficients {a(3,r)} the elements a(3,r) are given by a(3,r) = sin(2πrf g /f s ); means for selectively applying the first, the second and the third set of coefficients {a(q,r)} to the second multiplying means; third coupling means for coupling the output circuit of the second multiplying means to the input circuit of the first adder means.