Discrete Fourier Transform in an integrated circuit device
First Claim
1. Circuitry for performing a Discrete Fourier Transform operation, said circuitry comprising:
- a floating-point addition stage for adding mantissas of input values of said Discrete Fourier Transform operation; and
a fixed-point stage for multiplying outputs of said floating-point addition stage by twiddle factors, said fixed-point stage comprising;
memory for storing a plurality of sets of twiddle factors, each of said sets including copies of a respective twiddle factor shifted by different amounts, andcircuitry for determining a difference between exponents of said outputs of said floating-point stage, and for using said difference as an index to select from among said copies of said respective twiddle factor in each of said sets.
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Abstract
Circuitry performing Discrete Fourier Transforms. The circuitry can be provided in a fixed logic device, or can be configured into a programmable integrated circuit device such as a programmable logic device. The circuitry includes a floating-point addition stage for adding mantissas of input values of the Discrete Fourier Transform operation, and a fixed-point stage for multiplying outputs of the floating-point addition stage by twiddle factors. The fixed-point stage includes memory for storing a plurality of sets of twiddle factors, each of those sets including copies of a respective twiddle factor shifted by different amounts, and circuitry for determining a difference between exponents of the outputs of the floating-point stage, and for using that difference as an index to select from among those copies of that respective twiddle factor in each of the sets.
346 Citations
28 Claims
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1. Circuitry for performing a Discrete Fourier Transform operation, said circuitry comprising:
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a floating-point addition stage for adding mantissas of input values of said Discrete Fourier Transform operation; and a fixed-point stage for multiplying outputs of said floating-point addition stage by twiddle factors, said fixed-point stage comprising; memory for storing a plurality of sets of twiddle factors, each of said sets including copies of a respective twiddle factor shifted by different amounts, and circuitry for determining a difference between exponents of said outputs of said floating-point stage, and for using said difference as an index to select from among said copies of said respective twiddle factor in each of said sets. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of configuring a programmable integrated circuit device as circuitry for performing a Discrete Fourier Transform operation, said method comprising:
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configuring logic of said programmable integrated circuit device as a floating-point addition stage for adding mantissas of input values of said Discrete Fourier Transform operation; and configuring logic of said programmable integrated circuit device as a fixed-point stage for multiplying outputs of said floating-point addition stage by twiddle factors, said fixed-point stage comprising; memory for storing a plurality of sets of twiddle factors, each of said sets including copies of a respective twiddle factor shifted by different amounts, and circuitry for determining a difference between exponents of said outputs of said floating-point stage, and for using said difference as an index to select from among said copies of said respective twiddle factor in each of said sets. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A programmable integrated circuit device comprising:
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logic configurable as a floating-point addition stage for adding mantissas of input values of said Discrete Fourier Transform operation; and logic configurable as a fixed-point stage for multiplying outputs of said floating-point addition stage by twiddle factors, said fixed-point stage comprising; memory for storing a plurality of sets of twiddle factors, each of said sets including copies of a respective twiddle factor shifted by different amounts, and circuitry for determining a difference between exponents of said outputs of said floating-point stage, and for using said difference as an index to select from among said copies of said respective twiddle factor in each of said sets. - View Dependent Claims (16, 17, 18, 19, 20, 21)
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22. A machine-readable data storage medium encoded with machine-executable instructions for configuring a programmable integrated circuit device as circuitry for performing a Discrete Fourier Transform operation, said instructions comprising:
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instructions to configure logic of said programmable integrated circuit device as a floating-point addition stage for adding mantissas of input values of said Discrete Fourier Transform operation; and instructions to configure logic of said programmable integrated circuit device as a fixed-point stage for multiplying outputs of said floating-point addition stage by twiddle factors, said fixed-point stage comprising; memory for storing a plurality of sets of twiddle factors, each of said sets including copies of a respective twiddle factor shifted by different amounts, and circuitry for determining a difference between exponents of said outputs of said floating-point stage, and for using said difference as an index to select from among said copies of said respective twiddle factor in each of said sets. - View Dependent Claims (23, 24, 25, 26, 27, 28)
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Specification