Abstract: A method to estimate parameters of a system to spread a spectrum of a first periodic signal according to a modulation period. An embodiment comprises sampling the first signal using a second periodic signal, determining based on the sampling result each occurrence where the first and second signals are synchronous, incrementing a first counter at each sampling, the first counter being reset at each said occurrence, storing at each said occurrence the last value of the first counter before the resetting, providing a third periodic signal at a first level when said last value is greater than a threshold and at a second level when said last value is smaller than the threshold, and determining the modulation period based on the period of the third signal.