A design of the stopband variable FIR digital filters using spectral parameter

Several applications in digital signal processing demand variable digital filters with arbitrary variable frequency response. However, the design method of filters having variable piecewise large attenuation characteristics in the stopband is not proposed. This paper describes the design method of variable FIR digital filters having changed piecewise large attenuation characteristics in the stopband. The basic idea is to represent the coefficients of variable transfer function as the polynomials using spectral parameter. We design each filter with difference stopband attenuation by successive projections method. Then we approximate the obtained filter coefficient by the polynomials using spectral parameter in the least-square sense.