Method for reducing computational errors in a useful band of a signal generated with a fourier transform, for fixed-point microprocessors

• US 6,411,977 B1
• Filed: 07/19/1999
• Issued: 06/25/2002
• Est. Priority Date: 10/06/1998
• Status: Expired due to Fees

• Current Assignee: Screen Service Broadcasting Technologies S.p.A.
• Original Assignee: M.B. International srl
• Inventors: Bargauan, Michele
• Primary Examiner(s): Mai, Tan V.
• Application Number:
  US09/356,554
• Time in Patent Office: 1,072 Days
• Field of Search: 708/403, 370/210
• US Class Current: 708/403
• CPC Class Codes: G06F 17/141 Discrete Fourier transforms

Abstract

A method for reducing computational errors in a useful band of a signal generated with a Fourier transform, particularly for fixed-point microprocessors, which comprises a step of shifting errors present in a signal due to Fourier transforms applied thereto, so that the errors straddle a frequency in which the information content of the signal is irrelevant.

Claims

1. A method for reducing computational errors in a useful band of a signal generated with a Fourier transform, for fixed-point microprocessors, comprising a step of shifting errors present in a signal due to Fourier transforms applied thereto, so that said errors straddle a frequency in which the information content of said signal is irrelevant.

2. The method according to claim 1, wherein if said signal is to be subjected to an inverse Fourier transform it is shifted and centered around the Nyquist frequency so as to shift said errors to a frequency band which is not of interest.

3. The method according to claim 2, further comprising the step of calculating the inverse Fourier transform of said signal.

4. The method according to claim 3, comprising, after the computation of the inverse Fourier transform, a step of rearranging the frequencies of said signal by modulating it with a unitary tone at the Nyquist frequency.

5. The method according to claim 4, wherein said modulation step consists in multiplying said signal alternately by 1 and by −

1.

6. The method according to claim 5, wherein said step that consists in multiplying said signal by −

1 consists in modifying coefficients of a last step of said inverse Fourier transform.

7. The method according to claim 1, wherein if said signal is to be subjected to a direct Fourier transform, said signal is modulated with a unitary tone.

8. The method according to claim 7, comprising, after the modulation step, a step of performing the direct Fourier transform of said signal.

9. The method according to claim 8, comprising a step of shifting the frequencies of said signal so that they straddle the Nyquist frequency.