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Poles Of A Normalized Chebyshev Filter

Syntax	fncpole(n)
See Also	fncheb , fnbpole , zero2pol

Description
Returns the poles of a normalized Chebyshev filter with n poles and ripple parameter eps, where n is an integer scalar and eps is a real or double-precision scalar such that 0 < eps < 1. Note that the poles come in conjugate pairs, so the corresponding polynomial is real. The return value is a complex column vector of length n with each element corresponding to a pole.

Example
The following program computes the poles corresponding to a 7 pole Chebyshev filter with .8 ripple parameter. It then converts the complex pole locations to polar coordinates (r, theta) and plots them.

clear
#
n      = 7
eps    = .8
p      = fncpole(n, eps)
r      = abs(p)
theta  = atan2(imag(p), double(p))
theta  = 180 * theta / PI
rmax   = 2.
rmajor = 2
tmajor = 4
style = "cross"
color = "black"
polar(r, theta, rmax, rmajor, tmajor, style, color)