Electrical computers: arithmetic processing and calculating – Electrical digital calculating computer – Particular function performed
Reexamination Certificate
1999-07-19
2002-06-25
Mai, Tan V. (Department: 2124)
Electrical computers: arithmetic processing and calculating
Electrical digital calculating computer
Particular function performed
Reexamination Certificate
active
06411977
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for reducing computational errors in the useful band of a signal generated with a Fourier transform, particularly for fixed-point microprocessors.
More particularly, the invention relates to a method for reducing frequency errors due to computational errors.
It is known that the direct or inverse execution of Fourier transforms on discrete signals to obtain a time-continuous signal requires data with a great dynamic range, especially when the number of samples transformed is large.
Scientific applications normally use floating-point notations which ensure adequate dynamic range and precision: this approach is also used by high-level applications, in which the cost of the processing hardware is a secondary factor which is overruled by the precision of the result to be obtained.
The use of algorithms such as a Fourier transform in consumer applications, however, requires implementation using low-cost processors, particularly fixed-point processors with a limited dynamic range (i.e., a small number of bits).
The use of this type of processor generates results whose errors are more noticeable at the frequencies close to zero.
As the number of points on which a transform is performed increases, a fixed-point processor introduces increasingly large errors which are particularly noticeable proximate to the zero frequency, as mentioned.
SUMMARY OF THE INVENTION
The aim of the present invention is therefore to provide a method for reducing computational errors in the useful band of a signal generated with a Fourier transform which allows to use fixed-point microprocessors and provide improved performance.
Within the scope of this aim, an object of the present invention is to provide a method for reducing computational errors in the useful band of a signal generated with a Fourier transform, wherein the noise due to the use of a fixed-point microprocessor can be shifted into the band of the signal that is not of interest for the specific application for which said signal is meant.
Another object of the present invention is to provide a method for reducing computational errors in the useful band of a signal generated with a Fourier transform which is particularly useful in the case of signals of the OFDM (Orthogonal Frequency Division Multiplex) type generated by a digital signal processor (DSP).
Another object of the present invention is to provide a method for reducing computational errors in the useful band of a signal generated with a Fourier transform, particularly for fixed-point microprocessors, which is highly reliable, relatively easy to provide and at competitive costs.
This aim, these objects and others which will become apparent hereinafter are achieved by a method for reducing computational errors in the useful band of a signal generated with a Fourier transform, particularly for fixed-point microprocessors, characterized in that it comprises a step of shifting errors present in a signal due to Fourier transforms applied to it, so that said errors straddle a frequency in which the information content of said signal is irrelevant.
REFERENCES:
patent: 4574311 (1986-03-01), Resnikoff et al.
patent: 5686669 (1997-11-01), Hernandez et al.
patent: 6144873 (2000-11-01), Madore et al.
patent: 6148037 (2000-11-01), Abe
Josif Albert
M.B. International S.r.L.
Mai Tan V.
Modiano Guido
O'Bryne Daniel
LandOfFree
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