EP0356597A1
Expired / Lapsed
EP
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Improvement to digital filter sampling rate conversion method and device
Assignee: International Business Machines Corp
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Filing: 1988-08-30
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Granted: —
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Expires: 2008-08-30
Abstract
Abstract A digital filter providing output samples at a rate B while input samples are being provided at a rate A. The filter impulse response h(t) is sampled at a rate P = a.A = b.B, with P being the lowest common multiple to A and B, to derive Np filter coefficients (Ci) therefrom. Said coefficients are arranged into "a" sets of Np/a coefficients and stored. Output samples are then computed by feeding input samples Sn at incoming rate while permutating the sets of coefficients and generating output samples at said output rate.
Inventors
- 👤 Jacques Belloc
- 👤 Claude Galand
- 👤 Emmanuel Lancon
- 👤 André Milewski
- 👤 Michel Quintin
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-30 22:41
CPC Classifications
H; H03; H03H; H03H17/00; H03H17/02; H03H17/06; H03H17/0621; H03H17/0635; H03H17/0685
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
135 words
A process for performing a digital signal filtering function with a filter impulse response h(t) while operating a rate conversion for providing filtered output samples at a rate B while the filter is being fed at an input rate A, said process including: - deriving Np filter coefficients C(i), i = 0, 1, ..., Np-1, corresponding to said impulse response being sampled at a rate P, with: P = a.A = b.B, wherein "a" and "b" are integer values; - splitting said coefficients into "a" sets, Set(i), each including N′p/a coefficients with N′p being substantially equal to Np and storing said sets of coefficients; - computing "a" output samples while "b" input samples are being fed into the filter, each output sample computation involving using one Set(i), i being repetitively permutated in a predefined order.
Claim 2
Dependent Claim
135 words
A process for performing a digital signal filtering function with a filter impulse response h(t) while operating a rate conversion for providing filtered output samples at a rate B while the filter is being fed at an input rate A, said process including: - deriving Np filter coefficients C(i), i = 0, 1, ..., Np-1, corresponding to said impulse response being sampled at a rate P, with: P = a.A = b.B, wherein "a" and "b" are integer values; - splitting said coefficients into "a" sets, Set(i), each including N′p/a coefficients with N′p being substantially equal to Np and storing said sets of coefficients; - computing "a" output samples while "b" input samples are being fed into the filter, each output sample computation involving using one Set(i), i being repetitively permutated in a predefined order.
Claim 3
Dependent Claim
13 words
A process according to claim 1 wherein A and B are relatively prime.
Claim 4
Dependent Claim
25 words
A process according to claim 1 or 2, wherein "a" and "b" are computed for P being the lowest multiple to both A and B.
Claim 5
Dependent Claim
25 words
A process according to claim 1, 2 or 3 wherein said filter coefficients are derived from said impulse response h(t) being sampled at rate P.
Claim 6
Dependent Claim
38 words
A process according to claim 4, wherein said filter coefficients sets are permutated for each new set index being defined as the reminder of the division by "a" of "b" added to previous set order i old .
Claim 7
Dependent Claim
50 words
A process according to claim 4 wherein said filter input rate A is higher than output rate B, whereby each output sample computation involves shifting the input samples k positions into said filter, with k being the quotient of the division of "a" plus previous coefficient set index, by "b".
Claim 8
Dependent Claim
179 words
A digital filter having a predefined impulse response h(t) for filtering an input signal sampled at a rate A into a filtered output signal sampled at a rate B, said filter including a shift register provided with taps, a set of multipliers having one input connected to one of said taps respectively, adding means connected to said multipliers, and storage means for storing filter coefficients to be applied to a second multiplier input, said filter being characterized in that it includes: - means for sampling h(t) at a rate substantially equal to the lowest common multiple P of A and B, and deriving therefrom Np filter coefficients; - means for arranging a number N′p of said coefficients, N′p being substantially equal to Np, into sets of coefficients, Set(i); - means for feeding said input signal samples into said shift register at said input rate; and, - means for fetching sets of filter coefficients in a predetermined order and applying said coefficients to said multipliers at a rate B; whereby the output samples are being generated at said B rate.
Claim 9
Dependent Claim
179 words
A digital filter having a predefined impulse response h(t) for filtering an input signal sampled at a rate A into a filtered output signal sampled at a rate B, said filter including a shift register provided with taps, a set of multipliers having one input connected to one of said taps respectively, adding means connected to said multipliers, and storage means for storing filter coefficients to be applied to a second multiplier input, said filter being characterized in that it includes: - means for sampling h(t) at a rate substantially equal to the lowest common multiple P of A and B, and deriving therefrom Np filter coefficients; - means for arranging a number N′p of said coefficients, N′p being substantially equal to Np, into sets of coefficients, Set(i); - means for feeding said input signal samples into said shift register at said input rate; and, - means for fetching sets of filter coefficients in a predetermined order and applying said coefficients to said multipliers at a rate B; whereby the output samples are being generated at said B rate.
References Cited (Backward Citations)
FR2326079A1
Cited
EP0305864A2
Cited
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