Filter Design Toolbox™

cheby2 - Chebyshev Type II filter using specification object

Syntax

hd = design(d,'cheby2')
hd = design(d,'cheby2',designoption,value,designoption,
value,...)

Description

hd = design(d,'cheby2') designs a Chebyshev II IIR digital filter using the specifications supplied in the object d.

hd = design(d,'cheby2',designoption,value,designoption,
value,...) returns a Chebyshev II IIR filter where you specify design options as input arguments.

To determine the available design options, use designopts with the specification object and the design method as input arguments as shown.

designopts(d,'method')

For complete help about using cheby1, refer to the command line help system. For example, to get specific information about using cheby2 with d, the specification object, enter the following at the MATLAB prompt.

help(d,'cheby2')

Examples

These examples use filter specification objects to construct Chebyshev type I filters. In the first example, you use the matchexactly option to ensure the performance of the filter in the passband.

d = fdesign.lowpass;
hd = design(d,'cheby2','matchexactly','passband')


hd =

         FilterStructure: 'Direct-Form II, Second-Order Sections'
              Arithmetic: 'double'
               sosMatrix: [5x6 double]
             ScaleValues: [6x1 double]
        PersistentMemory: false

cheby2 also design highpass, bandpass, and bandstop filters. Here is a highpass filter where you specify the filter order, the stopband edge frequency. and the stopband attenuation to get the filter exactly as required.

d = fdesign.highpass('n,fst,ast',5,20,55,50)

d =
                Response: 'Highpass' 
          Specification: 'N,Fst,Ast'
            Description: {3x1 cell} 
    NormalizedFrequency: false      
                     Fs: 50         
            FilterOrder: 5          
                  Fstop: 20         
                  Astop: 55         

hd=design(d,'cheby2')
 
hd =
 FilterStructure: 'Direct-Form II, Second-Order Sections'
      Arithmetic: 'double'
       sosMatrix: [3x6 double]
     ScaleValues: [4x1 double] 
PersistentMemory: false

The Filter Visualization Tool shows the highpass filter meets the specifications.

fvtool(hd)

By design, cheby2 returns filters that use second-order sections. For many applications, and for most fixed-point applications, SOS filters are particularly well-suited for use.

See Also

butter, cheby1, ellip

cheby1

cl2tf