init

FOTF Toolbox/iir_pade.m

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+function H=iir_pade(r,a,n,T)
+% iir_pade - design IIR filter with Pade approximants  
+%
+%   H=iir_pade(r,a,n,T)
+%
+%   r - the fractional order
+%   a - weighting factor
+%   n - the filter order
+%   T - sample time
+   
+% Copyright (c) Dingyu Xue, Northeastern University, China
+% Last modified 18 May, 2022 
+   arguments, r(1,1) double, a(1,1){mustBeInRange(a,0,1)}=0
+      n(1,1){mustBePositiveInteger}=3
+      T(1,1){mustBePositive}=0.01
+   end
+   syms x, b=(3+a-2*sqrt(3*a))/(3-a); 
+   k0=6*b/T/(3-a); f=((1-x^2)/(1+b*x)^2)^r;
+   c=taylor(f,x,'Order',2*n); c=sym2poly(c);
+   c=c(end:-1:1); [N,D]=padefcn(c,n-1,n);
+   H=k0^r*tf(N(end:-1:1),D(end:-1:1),'Variable','z^-1','Ts',T);
+end