The present invention relates to real time spectral analysis of wide-band sampled signals, in particular to a method and system for real time digital spectral analysis of wide-band sampled signals using parallel processing techniques. The center frequency of each received wide-band signal is shifted by a small fraction .epsilon. of its bandwidth. After sampling and digitizing, the wide-band signals are de-multiplexed into N parallel sample streams for parallel processing. The sample streams are digitally FIR filtered and sub-band signals are determined by decimating the sample streams by a factor of 2.sup.kN;k=0,1, . . . , wherein only every 2.sup.kN.sup.th;k=0,1, . . . sample is retained and the others are discarded. These sub-band signals may then be processed using various methods of spectral analysis such as cross-correlation, auto-correlation or phased array applications. Any finite-length FIR filter has a finite transition band. After decimation, the transition band outside sub-band boundaries will suffer aliasing, which causes signals to falsely appear as aliased signals within the sub-band. Shifting all spectral features in the wide-band spectrum with a frequency shift .epsilon. prevents false correlation of the aliased signals.