Left: An example of the FFT frequency circle showing the mapping of different m when the FFT size is N = 4. Right: Illustration of the new saving scheme of a _{ℓ m} , adopted to match the requirement of a large number of matrix operations. The lower half (red) is for the real part, and the upper half (cyan) is for the imaginary part. The real and imaginary parts of a _{ℓ m} for one m are distributed as shown by the black arrows.