Patent ID: 7164723

Claim:
A modulation apparatus using a mixed-radix fast Fourier transform (FFT), comprising: an input/output interface for selecting a memory for input/output among memories for input/output and FFT calculation, selecting one of four banks of the selected memory, and performing input and output on the selected bank; two N-word memories each having four banks used for input/output to the input/output interface and FFT calculation; a first data exchange for selecting a memory for FFT calculation among the memories for input/output to the input/output interface and FFT calculation, and connecting banks assigned to each butterfly input/output to 4 inputs of a butterfly calculation circuit for in-place calculation; a butterfly for performing a radix-4 butterfly and a radix-2 butterfly provided from the first data exchange with one circuit, and forming a symmetric reverse output; a second data exchange for selecting a memory for FFT calculation among the memories for input/output to the input/output interface and FFT calculation, and connecting banks assigned to each butterfly input/output to four outputs of a butterfly calculation circuit for in-place calculation; and an address generator for generating a bank index and an address for performing in-place calculation in a multi-bank memory structure.