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Structures for specification object with design method


filtstruct = validstructures(D)
C = validstructures(D,METHOD)
Cs = validstructures(D,...,'SystemObject',sysobjflag)


filtstruct = validstructures(D) returns a structure array containing all valid filter structures for the filter specification object, D, organized by design method. Each design method is a field in the structure array, filtstruct. The fields contain a cell array of character vectors.

C = validstructures(D,METHOD) returns the valid structures for the filter specification object, D, and the design method, METHOD, in a cell array of character vectors.

Cs = validstructures(D,...,'SystemObject',sysobjflag) returns the valid structures for designing a filter System object when sysobjflag is true. To use System objects, you must have the DSP System Toolbox™ product installed. When sysobjflag is false, the function returns valid structures for designing dfilt objects. Design methods and design options for filter System objects are not necessarily the same as those for dfilt objects.


Design a default lowpass filter specification object. Return all valid design methods and structures in a structure array. Display the fieldnames to see all valid design methods. Display the valid filter structures for the equiripple field.

D = fdesign.lowpass;
filtstruct = validstructures(D);

Create a highpass filter of order 50 with a 3-dB frequency of 0.2. Obtain the available structures for a Butterworth design.

D = fdesign.highpass('N,F3dB',50,0.2);
C = validstructures(D,'butter');

If you have DSP System Toolbox software installed, use the 'SystemObject',sysobjflag syntax to return valid structures for a filter System object:

Cs = validstructures(D,'butter','SystemObject',true);

Introduced in R2009a

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