Design of linear phase FIR filters using the nonuniform DCT

We propose a novel interpolation technique for the design of linear phase FIR filters on nonuniform frequency grids. In this paper, we introduce the NDCT and propose an efficient way to implement it. In our method, the interpolation problem is converted into the one of constructing orthonormal functions. The computational complexity is O(N²) which is comparable with the Lagrange and Newton interpolation methods. The advantage over the other interpolation techniques is that one can easily apply this method to a least squares approximation on nonuniformly frequency grids by truncating filter coefficients.