Patent ID: 6822692
Filing Date: 2004-11-23
Classification: H03H

Abstract:
A digital filter for filtering a digital input signal with variable filter length l, wherein the filter length of said digital filter (8) is switchable a function of a variable input clock frequency fin of the digital input signal without changing in the ratio between the input clock frequency fin and an output clock frequency fout of the filtered digital output signal which is output by said digital filter (8), wherein the digital filter (8) is of modular design composed of at least one digital filter module (20) comprising:(a) a filter coefficient circuit (26) for outputting filter coefficients to a multiplier device (29) which multiplies the filter coefficients output by said filter coefficient circuit (26) by the input data signal which is present at a first signal input (21) of the digital filter module (20), (b) an adder circuit (32) for adding the signal output by the multiplier device (29) to a multiplexer output signal which is output by a first multiplexer (45), and (c) a register circuit (41) which is composed of a plurality of registers (42) which are connected in series, the outputs of the registers (42) each being connected to an input (44) of said first multiplexer (45).