1. A band-pass filter with at least one passband, which is real, bidimensional, oriented along a phase axis and resulting from the product of two identical one-dimensional Hamming windows, a transfer function of each of these windows being: 6 X i &it; ( f ) = α i + ( 1 - α i ) &it; cos &it; π &it; ( f - f &it; &it; q i ) f0 i, f is a current frequency; &agr; i is a real number, included between and excluding 0 and 1; fq i is a central frequency of the passband; and f 0 i defines half of the passband centered on fq i.