| 1. |
- Eghbali, Amir, et al.
(författare)
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A method for the design of Farrow-structure based variable fractional-delay FIR filters
- 2013
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Ingår i: Signal Processing. - : Elsevier. - 0165-1684 .- 1872-7557. ; 93:5, s. 1341-1348
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a method to design variable fractional-delay (FD) filters using the Farrow structure. In the transfer function of the Farrow structure, different subfilters are weighted by different powers of the FD value. As both the FD value and its powers are smaller than 0.5, our proposed method uses them as diminishing weighting functions. The approximation error, for each subfilter, is then increased in proportion to the power of the FD value. This gives a new distribution for the orders of the Farrow subfilters which has not been utilized before. This paper also includes these diminishing weighting functions in the filter design so as to obtain their optimal values, iteratively. We consider subfilters of both even and odd orders. Examples illustrate our proposed method and comparisons, to various earlier designs, show a reduction of the arithmetic complexity.
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| 2. |
- Eghbali, Amir, et al.
(författare)
-
Conditions for Lth-band filters of order 2N as cascades of identical linear-phase FIR spectral factors of order N
- 2014
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Ingår i: Signal Processing. - : Elsevier. - 0165-1684 .- 1872-7557. ; 97:April
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents formulas for the number of optimization parameters (degrees of freedom) when designing Type I linear-phase finite-length impulse response (FIR) Lth-band filters of order 2N as cascades of identical linear-phase FIR spectral factors of order N. We deal with two types of degrees of freedom referred to as (i) the total degrees of freedom D-T, and (ii) the remaining degrees of freedom D-R. Due to the symmetries or antisymmetries in the impulse responses of the spectral factors, D-T roughly equals N/2. Some of these parameters are specifically needed to meet the Lth-band conditions because, in an Lth-band filter, every Lth coefficient is zero and the center tap equals 1/L. The remaining D-R parameters can then be used to improve the stopband characteristics of the overall Lth-band filter. We derive general formulas for D-R with given pairs of L and N. It is shown that for a fixed L, the choices of N, in a close neighborhood, may even decrease D-R despite increasing the arithmetic complexity, order, and the delay.
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