An FFT device for performing a Fast Fourier Transform (FFT) of an operand vector of length N is described. The FFT device comprises a control unit, a coefficient unit, and a transformation unit. The control unit controls a sequence of transformation rounds, the transformation rounds including two or more FFT rounds and further including or not including a window round. The control unit also maintains configuration data indicating for each of said transformation rounds whether the respective transformation round is an FFT round, a window-FFT round, or a window round. The coefficient unit provides transformation data. The transformation unit is arranged to receive the transformation data and to perform the respective linear transformation on the basis of the transformation data. A method for performing a Fast Fourier Transform is described as well.