Define Composite System Objects - MATLAB & Simulink (original) (raw)

This example shows how to define System objects that include other System objects. Define a bandpass filter System object™ from separate highpass and lowpass filter System objects.

Store System Objects in Properties

To define a System object from other System objects, store those other objects in your class definition file as properties. In this example, the highpass and lowpass filters are the separate System objects defined in their own class-definition files.

properties (Access = private) % Properties that hold filter System objects pLowpass pHighpass end

Complete Class Definition File of Bandpass Filter Composite System Object

classdef BandpassFIRFilter < matlab.System % Implements a bandpass filter using a cascade of eighth-order lowpass % and eighth-order highpass FIR filters.

properties (Access = private)
    % Properties that hold filter System objects
    pLowpass
    pHighpass
end

methods (Access = protected)
    function setupImpl(obj)
        % Setup composite object from constituent objects
        obj.pLowpass = LowpassFIRFilter;
        obj.pHighpass = HighpassFIRFilter;
    end
    
    function yHigh = stepImpl(obj,u)
        yLow = obj.pLowpass(u);
        yHigh = obj.pHighpass(yLow);
    end
    
    function resetImpl(obj)
        reset(obj.pLowpass);
        reset(obj.pHighpass);
    end
end

end

Class Definition File for Lowpass FIR Component of Bandpass Filter

classdef LowpassFIRFilter < matlab.System % Implements eighth-order lowpass FIR filter with 0.6pi cutoff

properties (Nontunable) % Filter coefficients Numerator = [0.006,-0.0133,-0.05,0.26,0.6,0.26,-0.05,-0.0133,0.006]; end

properties (DiscreteState) State end

methods (Access = protected) function setupImpl(obj) obj.State = zeros(length(obj.Numerator)-1,1); end

function y = stepImpl(obj,u)
  [y,obj.State] = filter(obj.Numerator,1,u,obj.State);
end

function resetImpl(obj)
  obj.State = zeros(length(obj.Numerator)-1,1);
end

end end

Class Definition File for Highpass FIR Component of Bandpass Filter

classdef HighpassFIRFilter < matlab.System % Implements eighth-order highpass FIR filter with 0.4pi cutoff

properties (Nontunable) % Filter coefficients Numerator = [0.006,0.0133,-0.05,-0.26,0.6,-0.26,-0.05,0.0133,0.006]; end

properties (DiscreteState) State end

methods (Access = protected) function setupImpl(obj) obj.State = zeros(length(obj.Numerator)-1,1); end

function y = stepImpl(obj,u)
  [y,obj.State] = filter(obj.Numerator,1,u,obj.State);
end

function resetImpl(obj)
  obj.State = zeros(length(obj.Numerator)-1,1);
end

end end

See Also

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