1.　Purpose

The Fourier transform has been widely used in the field of digital signal processing. This method is also utilized to demodulation of OFDM receiver side. In wireless communication systems, we must change the number of the fixed data point which use the Fourier transform, and we must also change it to obey the standards. We would like to change from the fixed data point to the variable data point. As a reason, we are troublesome that we change the fixed data point by every standard. The purpose of this text is we design FFT circuit.