Low latency digital filter and method
AssigneeATI Technologies, Inc.
InventorsRaghuram Behara, Thomas Meyer, Yiwen Yu, Ajay Bhaskaran, Raul Casas
Life of this patent
Estimating the term…
Abstract
A digital filter pre-calculates C(1)*S(n−1), C(2)*S(n−2) . . . C(p−1)*S(n−p+1), prior to the arrival of sample S(n). As such y ( n ) = ∑ k = 0 k = p - 1 C ( k ) * S ( n - k ) may be calculated as a result of a single further multiply and accumulate operation, upon arrival of the symbol S(n). This, significantly reduces the latency of the filter.
Claims18
A method of filtering a digital stream of symbols S(i) using a pth order finite impulse response filter having filter coefficients C(0)C(1) . . . C(p−1), said method comprising
- pre-calculating the sum
- ∑
- k
- =
- 0
- k
- =
- p
- -
- 1
-
- C
-
- (
- k
- )
- *
- S
-
- (
- n
- -
- k
- )
- between the arrival of the (n−1)th and nth symbol;
- upon arrival of the nth of said symbols, calculating
- Y
-
- (
- n
- )
- =
- ∑
- k
- =
- 0
- k
- =
- p
- -
- 1
-
- C
-
- (
- k
- )
- *
- S
-
- (
- n
- -
- k
- )
- using said pre-calculated sum, prior to the arrival of the (n+1)th of said symbols.
A digital filter, comprising a symbol buffer having p−1 storage locations for storing arriving symbols, a coefficient memory having p−1 storage locations;
- a counter for counting from k=0 to p−1;
- a multiply and accumulate (MAC) block for multiplying and accumulating C(k)*S(n−k) from said storage locations of said symbol buffer and said coefficient memory;
- said counter providing control signals to cause said MAC block to calculate,
- ∑
- k
- =
- 0
- k
- =
- p
- -
- 1
-
- C
-
- (
- k
- )
- *
- S
-
- (
- n
- -
- k
- )
- between the arrival of the n−1th and nth of said symbols;
- and, upon arrival of the nth of said symbols, calculate
- Y
-
- (
- n
- )
- =
- ∑
- k
- =
- 0
- k
- =
- p
- -
- 1
-
- C
-
- (
- k
- )
- *
- S
-
- (
- n
- -
- k
- )
- .
A digital filter, for filtering a signal of incoming symbols S(i);
- means for calculating
- ∑
- k
- =
- 0
- k
- =
- p
- -
- 1
-
- C
-
- (
- k
- )
- *
- S
-
- (
- n
- -
- k
- )
- between the arrival of the n−1th and nth of said symbols;
- and means for calculating
- Y
-
- (
- n
- )
- =
- ∑
- k
- =
- 0
- k
- =
- p
- -
- 1
-
- C
-
- (
- k
- )
- *
- S
-
- (
- n
- -
- k
- )
- ,
- upon arrival of the nth of said symbols.
Dependencies are inferred from the claim text.