Hi, I'm not quite sure what you are trying to do in terms of defining your own System object. I'll give you a very simple example of how to write a System object class file with one property and a step() method.
This System object will be called ExpVarBase, it is designed to take a base value with a default of exp(1) and the step method takes a scalar or vector input and raises the base to each element of the input vector.
classdef ExpVarBase < matlab.System
Base = exp(1);
function obj = ExpVarBase(varargin)
function y = stepImpl(obj, x)
y = obj.Base.^x;
You can use this file like this.
H = ExpVarBase;
input = 1i*linspace(0,4*pi,2000);
y = step(H,input);
xval = input./1i;
H = ExpVarBase('Base',2);
y = step(H,2);