Patent ID: 7492700

Claim:
Method for analysing an OFDM signal (r IF (t)) with an analysing device ( 40 ) having a signal section ( 20 ) with a bandwidth (BW A ) smaller than the bandwidth (BW OFDM ) of the OFDM signal, the OFDM signal (r IF (t)) transporting a series of data symbols (S 1 , S 2 , . . . ) on several orthogonal carrier frequencies, each data symbol (S 1 ) having a useful part ( 30 ) separated by a guard period ( 31 ) from neighbouring data symbols (S 2 ), comprising the steps of low pass filtering of the OFDM signal with a low pass filter ( 24 ) and shifting ( 26 ) the spectrum of the OFDM signal in order to obtain a frequency shifted filtered OFDM signal (r(i)), whereby the length (τ) of the impulse response (h(t)) of the low pass filter ( 24 ) is shorter than ¼ of the length (T GP ) of the guard periods ( 31 ) of the data symbols (S 1 , S 2 , . . . ).