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US4908787A
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Interpolator/decimator filter structure and a notch filter therefor
Assignee: Telent Technologies Services Ltd
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Filing: 1986-08-08
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Granted: 1990-03-13
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Expires: 2006-08-08
Abstract
Abstract A filter structure including a notch filter is designed to have a transmission zero at a frequency slightly displaced from one half of the lower sampling rate of the interpolator/decimator, and thus providing increase in attenuation at the half-rate frequency. The notch filter is comprised of two like all-pass-network filters and has feed forward and feedback connections, the latter connection including a coefficient multiplier. The feedback connection is made between a tapped output of the second of the network filters and an input node. The tapped filter is characterized by throughput and a tapped output transform functions X(Z) and Y(Z) given by the following expressions: X(Z)=[Z-1-K]/[1-KZ-1 ; and, Y(Z)= alpha Z-1/[1-KZ-1 ; where Z-1 is the unit delay operator, K the multiplier coefficient and, alpha , a structure dependant constant.
Inventors
- 👤 Nigel P. Dyer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 19:09
CPC Classifications
H; H03; H03H; H03H17/00; H03H17/02; H03H17/0248; H03H17/0264; H03H17/0273; H03H17/0277; H03H17/0279; H03H17/025; H03H17/04; H03H17/0416; H03H17/0427; H03H17/0438; H03H17/0444; H03H17/045
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
112 words
A filter structure, operable between a lower and a higher sampling rate comprising: a switched branched network, having at least two branches including one or more all-pass-network filters, said switched branched network connected in series with a notch filter having a transmission zero at a frequency displaced from a frequency of one half of the lower sampling rate, said notch filter being comprised of a plurality of all-pass-network filters; each all-pass-network filter including a delay element and at least one coefficient multiplier and having as a characteristic a transform function X(Z) of the form: X(Z)=(Z.sup.-1 -K) / (1-KZ.sup.-1) where Z 1 is the unit delay operator and K is the multiplier coefficient.
Claim 2
Dependent Claim
112 words
A filter structure, operable between a lower and a higher sampling rate comprising: a switched branched network, having at least two branches including one or more all-pass-network filters, said switched branched network connected in series with a notch filter having a transmission zero at a frequency displaced from a frequency of one half of the lower sampling rate, said notch filter being comprised of a plurality of all-pass-network filters; each all-pass-network filter including a delay element and at least one coefficient multiplier and having as a characteristic a transform function X(Z) of the form: X(Z)=(Z.sup.-1 -K) / (1-KZ.sup.-1) where Z 1 is the unit delay operator and K is the multiplier coefficient.
Claim 3
Dependent Claim
103 words
A filter structure, as claimed in claim 1, wherein the notch filter comprises: a pair of all-pass-network filters connected in-line between an input node and an output node, an input to the first one of the pair of filters being connected to the output node, and a tapped output of the second one of these filters being connected to the input node, and wherein each all-pass-network filter is defined by a throughout transform function X(Z): X(Z)=(Z.sup.-1 K) / (1-KZ.sup.-1), and wherein the second of these filters has an intermediate transform function Y(Z): Y(Z) =α Z.sup.-1 / (1-KZ.sup.-1) where α is a structure constant.
Claim 4
Dependent Claim
68 words
A filter structure, as claimed in claim 2, wherein each all-pass-network filter comprises a delay element and a coefficient multiplier, each in a respective branch of the switched branched network and disposed between a common input terminal and an output node; branch nodes being located between the input terminal and the delay element and multiplier, these being cross-coupled to the outputs of the multiplier and delay element, respectively.
Claim 5
Dependent Claim
64 words
A filter structure, as claimed in claim 2, wherein each all-pass-network filter comprises a delay element in-line between an input node and an output node, there being a feedback connection between the output of the delay element and the input node, and, a feed forward connection between the input to the delay element and the output node, each connection including a like coefficient multiplier.
Claim 6
Dependent Claim
99 words
A notch filter, for use in a filter structure, said notch filter comprising: a pair of all-pass-network filters having a plurality of branches connected in-line between an input node and an output node, an input to the first one of the pair of filters being connected to the output node, and a tapped output of the second one of these filters being connected to the input node, and wherein transform function X(Z): X(Z)=(Z.sup.-1 K) / (1-KZ.sup.-1), and wherein the second of these filters has an intermediate transform function Y(Z): Y(Z)=α Z.sup.-1 / (1-KZ.sup.-1) where α is a structure constant.
Claim 7
Dependent Claim
99 words
A notch filter, for use in a filter structure, said notch filter comprising: a pair of all-pass-network filters having a plurality of branches connected in-line between an input node and an output node, an input to the first one of the pair of filters being connected to the output node, and a tapped output of the second one of these filters being connected to the input node, and wherein transform function X(Z): X(Z)=(Z.sup.-1 K) / (1-KZ.sup.-1), and wherein the second of these filters has an intermediate transform function Y(Z): Y(Z)=α Z.sup.-1 / (1-KZ.sup.-1) where α is a structure constant.
Claim 8
Dependent Claim
67 words
A notch filter, as claimed in claim 5, wherein each all-pass-network filter comprises a delay element and a coefficient multiplier, each in a respective branch of the network filter and, disposed between a common input terminal and an output node; branch nodes being located between the input terminal and the delay element and multiplier, these being cross-coupled to the outputs of the multiplier and delay element, respectively.
Claim 9
Dependent Claim
64 words
A notch filter, as claimed in claim 5, wherein each all-pass-network filter comprises a delay element in-line between an input node and an output node, there being a feedback connection between the output of the delay element and the input node, and, a feed forward connection between the input to the delay element and the output node, each connection including a like coefficient multiplier.
References Cited (Backward Citations)
US4694414A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-03-12 | 1993-09-11 | 1994-03-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-03-12 | 1997-09-11 | 1998-03-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-03-12 | 2001-09-11 | 2002-03-13 | $7700.00 | Window Closed / Lapsed |