Contents Previous Next Subchapters

Normalized Chebyshev Filter Polynomials
Syntax fncheb(nepsnumoutdenout)
See Also fnbut , fncpole , fcplot

Description
Computes the numerator and denominator polynomials for a normalized Chebyshev filter with n poles, where n is an integer greater than 0. The real or double-precision scalar eps specifies the ripple parameter, 0 < eps < 1.

The input values of numout and denout have no effect. The output value of numout is set to the double-precision column vector corresponding to the numerator polynomial of the Chebyshev filter (numout is equal to the scalar 1 because normalized Chebyshev filters have no zeros). The output value of denout is set to the double-precision column vector corresponding to the denominator polynomial of the Chebyshev filter. The filter's response function is

     |numout[s]|2
     |---------|
     |denout[s]|

and it is near 1 for s in the interval
           __
     [0, \/-1 ]
     
and near 0 for the rest of the positive imaginary axis.

Example
     numout   = novalue
     denout   = novalue
     n        = 3
     eps      = .8
     fncheb(n, eps,numout, denout)

     xmin   = 1e-2
     xmax   = 1e+2
     ymin   = 1e-4
     ymax   = 1e+1
     cutoff = 1.
     fcplot(xmin, xmax, ymin, ymax, cutoff, numout, denout)

returns the following plot: