A class of DS signal used in satellite TT&C whose ratio of information code duration to PN period is not integer is investigated in this paper and it can be modeled as non-periodic modulated DS signal. Besides, an estimation method for spread spectrum code of generic non-periodic modulated DS signal based on differential PCA is proposed. This method estimates sub-sequence, count and synchronous point of information code by calculating eigenvector corresponding to the largest eigenvalue of the covariance matrix of the differential sequence, thus solving the ambiguity problem of PN code in t...