Back to results
US 7,346,137 B1Granted
Nonuniform oversampled filter banks for audio signal processing
AssigneeAT&T Corp.
InventorZoran Cvetkovic
Life of this patent
Estimating the term…
Abstract
A non-uniform filter bank is created by joining sections of oversampled uniform filter bands that are based on complex exponential modulation (as opposed to cosine modulation). Each filter bank handles a given, non-overlapping frequency band. The bands are not of uniform bandwidth, and the filters of different banks have different bandwidths. The frequency bands of the different filter banks cover the frequency of interest with gaps in the neighborhoods of the filter band edges. A set of transition filters fills those gaps.
Claims3
An arrangement comprising:
- a collection of filters indexed by i, where i=0, 1, 2, . . . n1, wherein n1 is an integer less than N1, each having an input that is responsive to a different signal, where filter i has the transfer function
- V
- _
- 1
-
- (
- ⅇ
- j
-
- (
- ω
- -
- 2
-
- π
- N
- 1
-
- i
- )
- )
- ,
- and V is a time-reversed version of a filter V having high attenuation for frequencies ω>2π/N that is subject to the constraint that
- ∑
- i
- =
- 0
- N
- 1
- -
- 1
-
-
-
- V
- 1
-
- (
- ⅇ
- j
-
- (
- ω
- +
- 2
-
- π
- N
- 1
-
- i
- )
- )
-
- 2
- =
- N
- 1
- for all ω∈(−π, π);
- and
- a combiner for adding output signals of said filters to form an output signal of said arrangements.
58 more elements
A non-uniform filter bank comprising:
- a B plurality of filter bank sections, each spanning a chosen non-overlapping frequency band, where filter bank section j includes a filter Vj of bandwidth 2π/Nj and nj of its modulates, each responsive to a different signal and each developing an output signal, with said nj output signals combined to form an output of section j;
- and
- at least one transition filter for joining two adjacent filter bank sections j=k and j=k+1, that is a modulate of a filter Vk,k+1 with a shape of Vk+1 at positive frequencies and a shape of Vk at negative frequencies, with the latter scaled by √{square root over (Nk/Nk+1)}.
Dependencies are inferred from the claim text.