Patent ID: 8155244

Claim:
A method to demodulate an unknown signal with an unknown linear modulation, the method comprising: sampling said unknown signal at a sampling rate to produce a sampled signal; applying carrier frequency offset estimation to said sampled signal to match the frequency of said sampled signal to that of said unknown signal and to change constellation rotation of said sampled signal; utilizing symbol period estimation to match said sampling rate of said sampled signal to a sampling rate of said unknown signal; applying blind equalization to said sampled signal to provide an equalized unknown signal; and demodulating said equalized unknown signal by utilizing a multistep windowed histogram clustering algorithm to generate constellation clusters, wherein: said multistep windowed histogram clustering algorithm comprises: (a) setting a minimal histogram clustering window; (b) computing windowed histogram clustering; (c) computing a separation metric to set the length of a time window for rotation of said constellation; and (d) incrementally increasing a size of the histogram clustering window until the separation metric shows no further improvement applying a rotation rate estimation algorithm to said clusters to estimate a phase rotation rate; and utilizing said phase rotation rate estimate to de-rotate said clusters.