An FFT device for performing a Fast Fourier Transform of an operand vector of length N, comprising: a control unit arranged to control a sequence of transformation rounds, the transformation rounds including two or more FFT rounds, wherein the FFT rounds include a window-FFT round or the transformation rounds further include a window round, wherein each transformation round comprises a sequence of N/M successive operations, each operation being a linear transformation transforming a subvector of length M of said operand vector into a corresponding transformed subvector of length M; and a coefficient unit (14, 22) for providing transformation data; and a transformation unit (26, 27) arranged to receive, for each of said transformation rounds, transformation data (8.4; 8.6, 8.10) from the coefficient unit, the transformation data depending on whether the respective transformation round is an FFT round (8.10, 8.11), a window-FFT round (8.6-8.9), or said window round (8.4-8.7), and to perform the respective linear transformation on the basis of the transformation data, wherein the transformation data for an FFT round comprises a set of twiddle coefficients, the transformation data for a window-FFT round comprises a set of modified twiddle coefficients, and the transformation data for a window round comprises a set of window coefficients; and wherein the coefficient unit (14, 22) comprises or is integrated in a Random Access Memory unit, the RAM unit comprising a set of memory blocks, each memory block being readable as a whole within a single clock-cycle, wherein the set of memory blocks comprises: a subset of window memory blocks, each of said window memory blocks providing the window coefficients for a respective operation of the window round, or a subset of window-FFT memory blocks, each of said window-FFT memory blocks providing the modified twiddle coefficients for a respective operation of the window-FFT round, and wherein the set of memory blocks further comprises: a subset of FFT memory blocks providing the set of twiddle coefficients or a reduced set of twiddle coefficients. a control unit arranged to control a sequence of transformation rounds, the transformation rounds including two or more FFT rounds, wherein the FFT rounds include a window-FFT round or the transformation rounds further include a window round, wherein each transformation round comprises a sequence of N/M successive operations, each operation being a linear transformation transforming a subvector of length M of said operand vector into a corresponding transformed subvector of length M; and a coefficient unit (14, 22) for providing transformation data; and a transformation unit (26, 27) arranged to receive, for each of said transformation rounds, transformation data (8.4; 8.6, 8.10) from the coefficient unit, the transformation data depending on whether the respective transformation round is an FFT round (8.10, 8.11), a window-FFT round (8.6-8.9), or said window round (8.4-8.7), and to perform the respective linear transformation on the basis of the transformation data, wherein the transformation data for an FFT round comprises a set of twiddle coefficients, the transformation data for a window-FFT round comprises a set of modified twiddle coefficients, and the transformation data for a window round comprises a set of window coefficients; and wherein the coefficient unit (14, 22) comprises or is integrated in a Random Access Memory unit, the RAM unit comprising a set of memory blocks, each memory block being readable as a whole within a single clock-cycle, wherein the set of memory blocks comprises: a subset of window memory blocks, each of said window memory blocks providing the window coefficients for a respective operation of the window round, or a subset of window-FFT memory blocks, each of said window-FFT memory blocks providing the modified twiddle coefficients for a respective operation of the window-FFT round, and wherein the set of memory blocks further comprises: a subset of FFT memory blocks providing the set of twiddle coefficients or a reduced set of twiddle coefficients. a subset of window memory blocks, each of said window memory blocks providing the window coefficients for a respective operation of the window round, or a subset of window-FFT memory blocks, each of said window-FFT memory blocks providing the modified twiddle coefficients for a respective operation of the window-FFT round, and wherein the set of memory blocks further comprises: a subset of FFT memory blocks providing the set of twiddle coefficients or a reduced set of twiddle coefficients.