cheby2
Chebyshev Type II filter design
Syntax
Description
[
designs
a lowpass, highpass, bandpass, or bandstop Chebyshev Type II
filter, depending on the value of b,a
] = cheby2(n
,Rs
,Ws
,ftype
)ftype
and the
number of elements of Ws
. The resulting bandpass
and bandstop designs are of order 2n
.
Note: See Limitations for information about numerical issues that affect forming the transfer function.
[
designs
a lowpass, highpass, bandpass, or bandstop digital Chebyshev Type II filter and returns its zeros, poles, and gain. This
syntax can include any of the input arguments in previous syntaxes.z,p,k
] = cheby2(___)
Examples
Input Arguments
Output Arguments
More About
Algorithms
Chebyshev Type II filters are monotonic in the passband and equiripple in the stopband. Type II filters do not roll off as fast as Type I filters, but are free of passband ripple.
cheby2
uses a five-step algorithm:
It finds the lowpass analog prototype poles, zeros, and gain using the function
cheb2ap
.It converts poles, zeros, and gain into state-space form.
If required, it uses a state-space transformation to convert the lowpass filter into a bandpass, highpass, or bandstop filter with the desired frequency constraints.
For digital filter design, it uses
bilinear
to convert the analog filter into a digital filter through a bilinear transformation with frequency prewarping. Careful frequency adjustment the analog filters and the digital filters to have the same frequency response magnitude atWs
orw1
andw2
.It converts the state-space filter back to transfer function or zero-pole-gain form, as required.
Extended Capabilities
Version History
Introduced before R2006a