Loading patent…
AssigneeAlcatel
InventorMichael Walker
Estimating the term…
In the domain of telecommunications, the Fourier Transformation, frequently in the variant Fast Fourier Transformation, or FFT in short, is used, for example, in methods for echo suppression, for noise reduction, for improving speech recognition and for coding audio and video signals. In the case of the FFT, the number of frequencies N and the number of sampling values K are equal, the frequency spacing is constant, the bandwidth is constant, and the delay between the time signal and the frequency spectrum is fixed. These characteristics do not permit adaptation to, for example, psychoacoustic features, the frequency resolution of the human ear being nonlinear. The invention discloses a Continuous Fourier Transformation (CFT), that allows a sliding determination of the fourier transformation instead of former block processing according to the FFT. Further the number of frequency samples and the frequency distribution can be chosen freely and independently from the time sample rate.
Method for performing a Fourier Transformation which is especially adapted to the transmission function of human sensory organs, by which a time function x(k) is mapped out of the time domain into the frequency domain as a sum of frequency lines X(n) with a defined number of frequency lines and a defined frequency distribution, characterized in, that
Arrangement for transforming a time function x(k) out of the time domain into the frequency domain, characterized in that, following the convolution with the cosine and sine sampling values of the frequency line X(n), the time signal (x(k)) is supplied to a filter for the real component and to a filter for the imaginary component and the outputs of the filters are connected to an absolute-value generator |X(n)| from the output of which the absolute value of a frequency line X(n) is provided.
Arrangement for transforming the frequency function out of the frequency domain into the time domain, characterized in that, following the weighting of the real component of a filter function with the absolute sample value of the frequency line |X(n)| and with a cosine sample value cos(cnk) and the weighting of the imaginary component of a filter function with the absolute sample value of the frequency line |X(n)| and with a sine sample value sin(cnk), the resulting real component and imaginary component are both supplied to a summing unit summing up each of said real component and imaginary component over all frequencies to obtain an output time value y(k).
Dependencies are inferred from the claim text.