Fractional order filters in Simulink

Hi guys,

I'd like to check the behaviour of my system using fractional order filters. Basically, I'd like to have a way to implement filters with -2db/decade to -20db/decade with step of -2. The filters are in the figure.

So this is my code in Matlab but I'm not sure how to implement it in Simulink.

p = 0.1:0.1:1;
w = logspace(-4,10,500000);
for i = 1:10
Fr = @(w) 80./((Tcc1*j*w)+1).^p(i);
figure(5)
semilogx(w,20*log10(abs(Fr(w))))
hold on
end
title('Fractional order filters');
xlabel('Frequency [rad/s]');
ylabel('Magnitude [dB]');

So my best guess so far was to use MATLAB function block and compute the magnitude in linear scale like in the figure below.

And the code for this one would be:

function y = fcn(u)
Tcc1 = 5.3052e-05;
y = 20*log(abs(1./((Tcc1*j*u)+1)^0.5));
y = u;

Any ideas? Thanks in advance!

[Marko]

I managed to do it in the meanwhile but I will answer my own question if anyone ever comes across a similar request. So the idea is semi-correct. The function should be:

function y = fcn(u)
Tcc1 = 5.3052e-05;
y = 20*log10(abs(80./((Tcc1*j*u)+1)^1));

And the simulink model is:

And you should also make sure that f is the same as your signal frequency if it's a sinusoidal signal.