Fast Algorithms for Computing Composite-Number-Less-Than-20-Point DFT

In this paper, fast algorithms for computing composite-number-less-than-20-point DFT is developed, it is based on the matrix operation, makes as much use of the characteristics of twiddle factor, repeatedly transforms the twiddle factor matrix, finally, the core matrixs for computing N-point DFT is obtained. This paper provides the core matrix, calculation process and the amount of computation of less-than-20-point DFT. The algorithm is easy to be understood and applied.