Second order real allpass filter
AssigneeMagor Communications Corporation
InventorDean SWAN
Life of this patent
Estimating the term…
Abstract
A digital all-pass filter has an input port leading to an input sum block and a first feed forward path. Within the first feed forward path is a multiplier. The filter also has an output port coupled to an output sum block that receives a signal from the first feed forward path. A first feedback path is also provided from the output port to the input sum block. The first feedback path includes a multiplier therein. Nested within this structure is a first order all-pass filter having a feed forward path including a forward path delay and forward path that is delayed and a feedback path absent a separate delay element and beginning after the forward path delay element.
Claims22
A digital all-pass filter process described by a block diagram consisting of:
- an input port having an input sum block coupled thereto;
- an output port having an output sum block coupled thereto;
- a first feed forward path between the input port and a second input port of the output sum block and having a first feed forward multiplier block disposed therein;
- a first feedback path from the output port to a second input port of the input sum block and having a first feedback multiplier block disposed therein;
- a nested filter input port coupled to an output port of the input sum block and coupled to an input port of a nested input sum block;
- a nested filter output sum block;
- a nested multiplier block disposed between an output port of the nested filter input sum block and a first input port of the nested filter output sum block;
- a nested feed forward path between the nested filter input port and a second input port of the nested filter output sum block, the first feed forward path comprising a nested feed forward delay block;
- a delay block disposed between an output port of the nested filter output sum block and a first input port of the output sum block;
- and
- a nested feedback path coupled between the first input port of the output sum block and a second input port of the nested filter input sum block.
A method of forming a digital all-pass filter having coefficients maintained in lattice form, the method comprising:
- providing a first nth order filter, n>=1;
- providing a second mth order filter, m>=1;
- and,
- nesting the first nth order filter within the second mth order filter and using a single delay element in the place of two resulting delay elements within the nested n+mth order filter, the two resulting delay elements each from a different one of the nth order filter and the mth order filter.
A digital all-pass filter process described by a block diagram comprising:
- an input port having an input sum block coupled thereto;
- an output port having an output sum block coupled thereto;
- a first feed forward path between the input port and a second input port of the output sum block and having a first feed forward multiplier block disposed therein;
- a first feedback path from the output port to a second input port of the input sum block and having a first feedback multiplier block disposed therein;
- a nested filter input port coupled to an output port of the input sum block and coupled to an input port of a nested input sum block;
- a nested filter output sum block;
- a nested multiplier block disposed between an output port of the nested filter input sum block and a first input port of the nested filter output sum block;
- a nested feed forward path between the nested filter input port and a second input port of the nested filter output sum block, the first feed forward path comprising a nested feed forward delay block;
- a delay block disposed between an output port of the nested filter output sum block and a first input port of the output sum block;
- and
- a nested feedback path coupled between the first input port of the output sum block and a second input port of the nested filter input sum block.
Dependencies are inferred from the claim text.