A receiver and a method to demodulate an unknown signal with an unknown linear modulation is described. The method of one of various embodiments comprises: sampling the unknown signal at a sampling rate to produce a sampled signal; applying carrier frequency offset estimation to the sampled signal to match the frequency of the sampled signal to that of the unknown signal and to change constellation rotation of the sampled signal; utilizing symbol period estimation to match the sampling rate of the sampled signal to a sampling rate of the unknown signal; applying blind equalization to the sampled signal to provide an equalized unknown signal; and demodulating the equalized unknown signal by utilizing a multistep windowed histogram clustering algorithm to generate constellation clusters; applying a rotation rate estimation algorithm to the clusters to estimate a phase rotation rate; and utilizing the phase rotation rate estimate to de-rotate the clusters.