Integer-coefficient FIR filter sharpening for equiripple stopbands and maximally flat passbands

Linear-phase FIR filters with deep, equiripple stopbands are constructed using Chebyshev polynomials to sharpen short linear-phase subfilters. The Chebyshev recursion yields a natural implementation structure using only local interconnections between subfilter copies. Small-integer coefficients often suffice for the subfilters, because of their shallow stopbands, and power-of-two coefficients often suffice for the sharpening structure. Included are several passband-flattening techniques, most of which also use only small-integer coefficients.