Patent ID: 7945406

Claim:
A method for measuring a relative phase shift between a periodic digital test signal and a periodic digital reference signal, the method comprising: receiving at a sampling unit M periods of the test signal and M periods of the reference signal, each of the M periods of both the test signal and the reference signal having a period length T sig , M being a natural number greater than 1; sampling, by the sampling unit, the test signal to generate N sampled values at a sampling frequency f s =1/T s , whereby T s , is a period such that T s =(M*T sig )/N, N being a natural number greater than M; assigning each of the sampled values a different index value n, for which 0≦n≦N−1; calculating, by a calculation unit, a relative phase shift T φ between the test signal and the reference signal based on a value ∑ i = 0 M - 1 ⁢ Idx ⁡ ( i ) + K , K being a constant, i being a natural number, and Idx(i) corresponding to the index value n of the sampled values that are either (1) a first sampled value immediately after a zero crossing of the test signal during an i th period of the reference signal or (2) a last sampled value immediately before a zero crossing of the test signal.