Time-recursive lattice structure for IFFT in DMT application
AssigneeIndustrial Technology Reseach Institute
InventorsChi-Li Yu, An-Yeu Wu
Life of this patent
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Abstract
The present invention may significantly reduce the number of iteration of the time recursive IFFT structure. First, the real and imaginary part of the input signal are modified based on the symmetric and anti-symmetric. Then, they are mixed together by an adder and fed into the lattice module. Next, an IFFT is performed on the modified input data sequence to generate a transformed sequence. Through the symmetric and anti-symmetric properties, the redundant terms may be eliminated.
Claims18
A method for efficiently processing an Inverse Fast Fourier Transformation for a 2N point original input data sequence X(k), wherein said original input data sequence includes a real part Xr(k) and an imaginary part Xi(k) (k=0, . . . , N−1), comprising the steps of:
- identifying a first modification pattern;
- modifying said real part of original input data sequence based on said first modification pattern to form a modified real part X′r(k);
- identifying a second modification pattern;
- modifying said imaginary part of original input data sequence based on said second modification pattern to form a modified imaginary part Xi′(k);
- combing said modified real part Xr′(k) and modified imaginary part Xi′(k) together to form a modified input data X′(k);
- and
- inputting said modified input data X′(k) to an Inverse Fast Fourier transformation (IFFT) module to generate an output sequence.
An apparatus for efficiently processing an Inverse Fast Fourier Transformation for a 2N point original input data sequence X(k), wherein said original input data sequence includes a real part Xr(k) and an imaginary part Xi(k) (k=0, . . . , N−1), comprising:
- a modifying device for modifying said real part and imaginary part of original input data sequence according to a first and second identified modification pattern to form a modified input data X′(k);
- and
- an Inverse Fast Fourier transformation (IFFT) module for processing the Inverse Fast Fourier transformation (IFFT) for said modified input data X′(k), wherein said Inverse Fast Fourier transformation (IFFT) module further comprises:
- a plurality of lattice modules, said each lattice module receiving said modified input data X′(k) to generate the first and the second output signal;
- a plurality of calculating units, wherein any two calculating units are coupled to one lattice module for receiving the first and the second output signal of said lattice module, and one of said two calculating units for generating the difference of said first and second output signal and the other for generating the sum of said first and second output signal;
- and
- a plurality of shifter, wherein each shifter is coupled to one of said calculating units for receiving the output signal to shift right by log2(2N) bits of said received output signal.
A method for efficiently processing an Inverse Fast Fourier transforming for an 2N point original input data sequence X(k), wherein said original input data sequence includes a real part Xr(k) and an imaginary part Xi(k) (k=0, . . . , N−1), comprising the steps of:
- modifying said real part of original input data sequence to Xr(k)+(−1)n·Xr(N−k) and n=0, 1, . . . , N−1;
- modifying said imaginary part of original input data sequence to Xi(k)+(−1)n+1·Xi(N−k) and n=0, 1, . . . , N−1;
- combing said modified real part and modified imaginary part together to form modified input data;
- and
- inputting said modified input data to an Inverse Fast Fourier transformation (IFFT) module to generate an output sequence.
Dependencies are inferred from the claim text.