Filter switching method

A filter apparatus having an input terminal, an output terminal, a digital FIR filter (1) comprising two or more sections (6,12) each of which has a control means (18,20,22) for setting the filter function of the respective section, an input switch means (24) and an output fader means (28,30,32), said input switch means (24) and said output fader means (28,30,32) being constructed and arranged relative to the input terminal, the output terminal and each of the sections (6,12) so as to be operable either to connect two or more sections in series between the input terminal and output terminal and thereby effectively form a first FIR filter (A) with a first filter function, or alternatively, to render inoperable one or more, sections by fading out, its output signal whilst leaving one or more sections (6,12) connected in series between the input terminal and output terminal and thereby effectively form a second filter (B) with a second FIR filter function without disrupting the passage of a signal through the filter apparatus from the input terminal to the output terminal, said control means (18,20,22,24,26) being operable to change the filter function of the inoperable section or sections.

A digital FIR filter (1) apparatus which is selectively changeable from a first digital FIR filter to a second digital FIR filter with a different filter function, while permitting uninterrupted passage of a signal therethrough to be filtered, the filter apparatus (1) comprising at least first and second filter sections (6,12), each section comprising a series chain of delay elements (18) with intermediate tapping points (20), and scaler elements (22) with adjustable scaling coefficients being connected to respective tapping points (20), the outputs of the scalers (22) being connected to a summing means (24,26), wherein the output of the first and second section summing means (24,26) are coupled to respective first and second inputs of an output fader means (28,30,32) for providing a filter output, and wherein an input terminal of the digital filter apparatus (1) together with both ends of the series chains of both filter sections are selectively coupled together via an input switch means (24), whereby to permit the output of one filter section to be faded out while its scaling coefficients are changed, and for the series chains of the filter sections to be selectively connected in series, either chain being upstream of the other.

A filter apparatus having an input terminal, an output terminal, a digital FIR filter (1) comprising two or more sections (6,12) each of which has a control unit (18,20,22) for setting the filter function of the respective section, an input switch (24) and an output fader (28,30,32), said input switch (24) and said output fader (28,30,32) being constructed and arranged relative to the input terminal, the output terminal and each of the sections (6,12) so as to be operable either to connect two or more sections in series between the input terminal and output terminal and thereby effectively form a first FIR filter (A) with a first filter function, or to render inoperable one or more, sections by fading out, its output signal whilst leaving one or more sections (6,12) connected in series between the input terminal and output terminal and thereby effectively form a second filter (B) with a second FIR filter function without disrupting the passage of a signal through the filter apparatus from the input terminal to the output terminal, said control unit (18,20,22,24,26) being operable to change the filter function of the inoperable section or sections.

A digital FIR filter (1) apparatus which is selectively changeable from a first digital FIR filter to a second digital FIR filter with a different filter function, while permitting uninterrupted passage of a signal therethrough to be filtered, the filter apparatus (1) comprising at least first and second filter sections (6,12), each section comprising a series chain of delay elements (18) with intermediate tapping points (20), and scaler elements (22) with adjustable scaling coefficients being connected to respective tapping points (20), the outputs of the scalers (22) being connected to a summing unit (24,26), wherein the output of the first and second section summing units (24,26) are coupled to respective first and second inputs of an output fader (28,30,32) for providing a filter output, and wherein an input terminal of the digital filter apparatus (1) together with both ends of the series chains of both filter sections are selectively coupled together via an input switch (24), whereby to permit the output of one filter section to be faded out while its scaling coefficients are changed, and for the series chains of the filter sections to be selectively connected in series, either chain being upstream of the other.