Method and apparatus of the variable points IFFT/FFT

An apparatus for performing a variable point Fast Fourier Transform (FFT), comprising:

• an FFT interpolator to receive input data having N1 points and output interpolated data signals having N2 points, the FFT interpolator including a plurality of interpolators, one of which is activated to output the interpolated data signals having N2 points based on the input data having N1 points, the one interpolator activated being selected according to a first FFT operation mode signal, wherein Ni is a number that is no greater than N2;
• an FFT operator to generate FFT operation data signals having N2 points by performing an FFT operation on the interpolated data signals having N2 points;
• an FFT mode selector to receive the FFT operation data signals having N2 points and output FFT data signals having N1 points, the FFT mode selector including a plurality of decimators, one of which is activated to output the FFT data signals having N1 points, the one decimator activated being selected according to a second FFT operation mode signal that corresponds to the first FFT operation mode signal provided to the FFT interpolator;
• and
• a control unit to output the first FFT operation mode signal and the second FFT operation mode signal.

An apparatus for performing a variable point IFFT/FFT, comprising:

• a butterfly operator receiving N pieces of input data and performing a butterfly operation on the input data;
• a demultiplexer outputting an input data signal equal to ½ point in N pieces of input data or a signal output by the butterfly operator;
• a first N/2 IFFT/FFT performing an IFFT/FFT operation on N/2 pieces of data received from the demultiplexer;
• a twiddle coefficient ROM multiplying the output of the butterfly operator by a twiddle coefficient;
• a second N/2 IFFT/FFT performing an IFFT/FFT operation on N/2 pieces of data received from the twiddle coefficient ROM;
• a bit reverse unit performing a bit reversing operation or output signals from the first N/2 IFFT/FFT and the second N/2 IFFT/FFT;
• and
• a control unit controlling operations of the butterfly operator, the twiddle coefficient ROM, and second N/2 IFFT/FFT.

A method of performing a variable point IFFT, comprising:

• receiving input data having Ni points at an IFFT interpolator;
• activating one of a plurality of interpolators associated with the IFFT interpolator to output interpolated data signals having N2 points, the one interpolator activated being selected according to a first IFFT operation mode signal, wherein N1 is a number that is no greater than N2;
• performing an IFFT operation on the interpolated data signals having N2 points to generate IFFT operation data signals having N2 points;
• receiving the IFFT operation data signals having N2 points at an IFFT mode selector and
• activating one of a plurality of decimators associated with the IFFT mode selector to output IFFT data signals having N1 points, the one decimator activated being selected according to a second IFFT operation mode signal that corresponds to the first IFFT operation mode signal provided to the IFFT interpolator.

A method of performing a variable point FFT, comprising:

• receiving input data having N1 points at an FFT interpolator;
• activating one of a plurality of interpolators associated with the FFT interpolator to output interpolated data signals having N2 points, the one interpolator activated being selected according to a first FFT operation mode signal, wherein N1 is a number that is no greater than N2;
• performing an FFT operation on the interpolated data signals having N2 points to generate IFFT operation data signals having N2 points;
• receiving the FFT operation data signals having N2 points at an FFT mode selector;
• and
• activating one of a plurality of decimators associated with the FFT mode selector to output FFT data signals having N1 points, the one decimator activated being selected according to a second FFT operation mode signal that corresponds to the first FFT operation mode signal provided to the FFT interpolator.