Filter Design Toolbox™

dfilt.cascade - Cascade of discrete-time filters

Syntax

Refer to dfilt.cascade in Signal Processing Toolbox™ documentation for more information.

Description

hd = dfilt.cascade(filterobject1,filterobject2,...) returns a discrete-time filter object hd of type cascade, which is a serial interconnection of two or more filter objects filterobject1, filterobject2, and so on. dfilt.cascade accepts any combination of dfilt objects (discrete time filters) to cascade, as well as Farrow filter objects.

You can use the standard notation to cascade one or more filters:

cascade(hd1,hd2,...)

where hd1, hd2, and so on can be mixed types, such as dfilt objects and mfilt objects.

hd1, hd2, and so on can be fixed-point filters. All filters in the cascade must be the same arithmetic format — double, single, or fixed. hd, the filter object returned, inherits the format of the cascaded filters.

Examples

Cascade a lowpass filter and a highpass filter to produce a bandpass filter.

[b1,a1]=butter(8,0.6);				% Lowpass
[b2,a2]=butter(8,0.4,'high');	% Highpass
h1=dfilt.df2t(b1,a1);
h2=dfilt.df2t(b2,a2);
hcas=dfilt.cascade(h1,h2)			% Bandpass with passband 0.4-0.6
hcas = 
         Filterstructure: Cascade
              Section(1): Direct Form II Transposed
              Section(2): Direct Form II Transposed
        PersistentMemory: false

To view the details of one filter section, use

hcas.section(1)
 ans =
          FilterStructure: 'Direct Form II Transposed'
              Arithmetic: 'double'
               Numerator: [1x9 double]
             Denominator: [1x9 double]
        PersistentMemory: false
                  States: [8x1 double]

See Also

dfilt, dfilt.parallel, dfilt.scalar

dfilt.calatticepc

dfilt.cascadeallpass