Patent ID: 8477876

Claim:
A method to search a digital transmission having unknown carrier and symbol frequencies in a modulated reception signal, comprising: performing successive trials of several carrier and symbol frequencies, using decreasing values of a currently tried symbol frequency; demodulating the modulated reception signal with a currently tried carrier frequency; filtering into a filtered signal the demodulated reception signal in a band having a width corresponding to the currently tried symbol frequency; producing successive samples of the filtered signal; for each currently tried symbol frequency: forming a complex indicator having a real component and an imaginary component established from the successive samples of the filtered signal such that the real component and the imaginary component have cyclostationary properties and such that one of the components tends to cancel when the other component tends towards a relative maximum; building a spectrum of variation of the complex indicator; searching for a singular spike in the spectrum; and determining the unknown symbol frequency from the frequency of the spike.