wc = 2*pi*20e3

%

Hs = tf(wc^2,[1 wc*sqrt(2), wc^2])

%

bode(Hs,{1e4,1e8})
grid

%

fs = 2*100*wc/(2*pi) % two decades above wc

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Ts = 1/fs

%

Hz = c2d(Hs, Ts)

%

step(Hz)