An apparatus for computing the discrete Fourier transform of a linear array variable f(j) of length N or of a planar array variable f(j, k) of dimensions N×M, wherein both N and M are even positive integers. The computation is divided into three parts, each suitable for computation via a multiprocessor array. Firstly, each element of the linear array f(j) is multiplied by the corresponding element of a first array constant. The resultant array is circularly convolved with a second array constant in the second step. The circular convolution may be computed in a straight forward manner or the second array constant may be resolved into N-1 simple array constants which are successively convolved. Lastly, each element of the resultant array after convolution is multiplied by the corresponding element of a third array constant. The invention is applied to a planar array by loading the planar array f(j,k) into corresponding elements of a planar array of processor elements. The above described process is first applied separately to the columns of the original planar array and then applied separately to the rows of the resultant planar array.
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