  If the phase retrieval problem can be solved by a method similar to that of
solving a system of linear equations under the context of FFT, the time
complexity of computer based phase retrieval algorithm would be reduced. Here I
present such a method which is recursive but highly non-linear in nature, based
on a close look at the Fourier spectrum of the square of the function norm. In
a one dimensional problem it takes $O(N^2)$ steps of calculation to recover the
phases of an N component complex vector. This method could work in 1, 2 or even
higher dimensional finite Fourier analysis without changes in the behavior of
time complexity. For one dimensional problem the performance of an algorithm
based on this method is shown, where the limitations are discussed too,
especially when subject to random noises which contains significant high
frequency components.
