Design of sharp FIR bandstop filters using quadrature masking filters

A novel computationally highly efficient realization of sharp symmetrical bandstop FIR filter is proposed. The new structure is derived using the frequency-response-masking technique, where the bandedge-shaping filter is derived from half-band filter by substituting each delay of the half-band filter by M delays. The masking filters are unconventional. They are quadrature filters derived from linear combinations of the masking filters in the conventional frequency-response-masking technique. Approximate expressions for the optimal value of M and the corresponding number of multipliers are derived.