An apparatus and method for processing a first electrical signal having a frequency interval I containing information, and increasing the signal-to-noise ratio thereof utilizes a mixer for shifting the frequencies of the first signal in the interval I to an interval I.sub.s. A plurality of filters, coupled in parallel, to the mixer pass, respectively, only frequencies in subintervals of I.sub.s, which are mutually disjoint. A second embodiment utilizes a plurality of mixers which shift, respectively, mutually disjoint subintervals of I such that their left end points are substantially equal. A plurality of filters, coupled, respectively, to the mixers, pass, respectively, only those frequencies in the shifted subintervals. Preferably, the frequency intervals passed by the filters in both embodiments are equal in bandwidth, and have no gaps therebetween.