EP0463473A2
Expired / Lapsed
EP
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Fast calculation apparatus for carrying out a forward and an inverse transform
Assignee: NEC Corp
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Filing: 1991-06-12
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Granted: —
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Expires: 2011-06-12
Abstract
Abstract In an apparatus for carrying out a linear transform calculation on a product signal produced by multiplying a predetermined transform window function and an apparatus input signal, an FFT part (23) carries out fast Fourier transform on a processed signal produced by processing the product signal in a first processing part (21). As a result, the FFT part produces an internal signal which is representative of a result of the fast Fourier transform. A second processing part (22) processes the internal signal into a transformed signal which represents a result of the linear transform calculation. The apparatus is applicable to either of forward and inverse transform units (11, 12). <IMAGE>
Inventors
- 👤 Masahiro Nec Corporation Iwadare
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-01 16:07
CPC Classifications
G; G06; G06F; G06F17/00; G06F17/10; G06F17/14; G06F17/147
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
152 words
An apparatus for carrying out a forward transform calculation on an apparatus input signal, said apparatus including multiplying means for multiplying a predetermined forward transform window function and said apparatus input signal to produce a product signal and transform carrying out means for carrying out a linear forward transform on said product signal to produce a forward transformed signal representative of a result of said linear forward transform, wherein said transform carrying out means comprises: first processing means connected to said multiplying means for processing said product signal into a processed signal; internal transform carrying out means connected to said first processing means for carrying out a forward fast Fourier transform on said processed signal to produce an internal signal representative of a result of said forward fast Fourier transform; and second processing means connected to said internal transform carrying out means for processing said internal signal into said forward transformed signal.
Claim 2
Dependent Claim
171 words
An apparatus as claimed in Claim 1, said multiplying means producing, as said product signal, a succession of zeroth through (N/4 - 1)-th and (N/4)-th through (N - 1)-th product data, where N represents an integral multiple of four, wherein said first processing means comprises: particular processing means connected to said multiplying means for processing said zeroth through said (N/4 - 1)-th product data into a succession of (3N/4) through N-th particular data having a first polarity in common; specific processing means connected to said multiplying means for processing said (N/4)-th through said (N - 1)-th product data into a succession of zeroth through (3N/4 - 1)-th specific data having a second polarity in common, said second polarity being different from said first polarity; and calculating means connected to said particular processing, said specific processing, and said internal transform carrying out means for calculating said processed signal by using a predetermined signal and each of said (3N/4) through said N-th particular and said zeroth through said (3N/4 - 1)-th specific data.
Claim 3
Dependent Claim
63 words
An apparatus as claimed in Claim 2, wherein said predetermined signal represents exp[-2πjn/(2N)] , said calculating means being for multiplying said exp[-2πjn/(2N)] and each of said (3N/4) through said N-th particular and said zeroth through the (3N/4 - 1)-th specific data to produce said processed signal, where j represents an imaginary unit, n being variable between 0 and N - 1, both inclusive.
Claim 4
Dependent Claim
135 words
An apparatus as claimed in Claim 2 or 3, wherein said calculating means comprises: combining means connected to said particular and said specific processing means for combining said particular and said specific data successions into a succession of zeroth through (N - 1 - 2p)-th and 2p-th through (N - 1)-th combined data, where p is variable between 0 and N/2 - 1, both inclusive; subtracting means connected to said combining means for subtracting said (N - 1 - 2p)-th combined datum from said 2p-th combined datum to produce a difference and a local signal representative of said difference; and internal multiplying means connected to said subtracting and said internal transform carrying out means for multiplying a predetermined and said local signals into an internal product to make said processed signal represent said internal product.
Claim 5
Dependent Claim
49 words
An apparatus as claimed in Claim 4, wherein said predetermined signal represents exp(-2πjp/N) , said internal multiplying means being for multiplying said exp(-2πjp/N) and said local signal to produce said processed signal, where j represents an imaginary unit, p being variable between 0 and N - 1, both inclusive.
Claim 6
Independent Claim
104 words
An apparatus as claimed in any one of Clams 1 to 5, said internal transform carrying out means producing, said internal signal, a succession of zeroth through (k - 1)-th and k-th through (N/2 - 1)-th internal data, where N represents an integral multiple of four, k being variable between 0 and N - 1, both inclusive, wherein said second processing means comprises internal multiplying means connected to said internal transform carrying out means for multiplying said k-th internal datum and exp[-2πj(k + 1/2)/(2N)] into a local product to make said forward transformed signal represent said local product, where j represents an imaginary number.
Claim 7
Independent Claim
149 words
An apparatus for carrying out an inverse transform calculation on an apparatus input signal, said apparatus including transform carrying out means for carrying out a linear inverse transform on said apparatus input signal to produce an inverse transformed signal representative of a result of said linear inverse transform and multiplying means for multiplying a predetermined inverse transform window function and said inverse transformed signal to produce a product signal, wherein said transform carrying out means comprises: first processing means for processing said apparatus input signal into a processed signal; internal transform carrying out means connected to said first processing means for carrying out an inverse fast Fourier transform on said processed signal to produce an internal signal representative of a result of said inverse fast Fourier transform; and second processing means connected to said internal transform carrying out means for processing said internal signal into said inverse transformed signal.
Claim 8
Dependent Claim
86 words
An apparatus as claimed in Claim 7, said apparatus input signal being a succession of zeroth through (N - 1)-th apparatus input data, where N represents an integral multiple of four, wherein said first processing means comprises first multiplying means for multiplying said zeroth through said (N - 1)-th apparatus input data and exp[2πj(N/4 + 1/2)k/N] into a first product to make said processed signal represent said first product, where j represents an imaginary unit, k being variable between 0 and N - 1, both inclusive.
Claim 9
Dependent Claim
103 words
An apparatus as claimed in Claim 7 or 8, said internal transform carrying out means producing, as said internal signal, a succession of zeroth through (N - 1)-th internal data, where N represents an integral multiple of four, wherein said second processing means comprises second multiplying means connected to said internal transform carrying out means for multiplying said zeroth through said (N - 1)-th internal data and exp[-2πj(n + N/4 + 1/2)/(2N)] into a second product to make said inverse transformed signal represent said second product, where j represents an imaginary unit, n being variable between 0 and N - 1, both inclusive.
Claim 10
Dependent Claim
126 words
An apparatus as claimed in Claim 7, 8 or 9, said apparatus input signal being a succession of through zeroth and (N/2 - 1)-th apparatus input data, where N represents an integral multiple of four, wherein said first processing means comprises: particular processing means for processing said 2k-th apparatus input datum into a k-th particular datum, where k is variable between 0 and N/2 - 1, both inclusive; specific processing means for processing said (2k + 1)-th apparatus input datum into a (N - 1 - k)-th specific datum; and calculating means connected to said particular and said specific processing means for calculating said processed signal by using a predetermined signal and each of said k-th particular and said (N - 1 - k)-th specific data.
Claim 11
Dependent Claim
35 words
An apparatus as claimed in Claim 10, said predetermined signal representing exp(2πjk/N) , where j represents an imaginary unit, wherein said internal calculating means is for multiplying said predetermined signal and said k-th particular datum.
Claim 12
Dependent Claim
261 words
An apparatus as claimed in Claim 7 or 86, said internal transform carrying out means producing, as said internal signal, a succession of zeroth through (p - 1)-th and p-th through (N/2 - 1)-th internal data, where N represents an integral multiple of four, p being variable between 0 and (N/2 - 1), both inclusive, wherein said second processing means comprises: multiplying means connected to said internal transform carrying out means for multiplying said p-th internal datum and exp[2πj(p + 1/2)/2N] into a local product to make said inverse transformed signal represent said local product, j representing an imaginary unit, said local product being a succession of zeroth through (N/4 - 1)-th and (N/4)-th through (N/2 - 1)-th product data; particular processing means connected to said multiplying means for processing said zeroth through said (N/4 - 1)-th product data into a first succession of (3N/4 - 1)-th through (N/2)-th particular data in a descending order and a second succession of (3N/4)-th through N-th particular data in an ascending order, the particular data of said first and said second successions having a first polarity in common; and specific processing means connected to said multiplying means for processing said (N/4)-th through (N/2 - 1)-th product data into a first succession of zeroth through (N/4 - 1)-th specific data in an ascending order and a second succession of (N/2 - 1)-th through (N/4)-th specific data in a descending order, the specific data of said first and said second successions having a second polarity in common, said second polarity being different from said first polarity.
References Cited (Backward Citations)
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