# Can you plot an irrational transfer function on matlab?

For example if I have the following transfer function:

$$H(s) = \frac{1}{\cosh(\sqrt{s/10})}$$

Can I do the bode plot it in matlab or do I need to rationalize it beforehand?

• What have you tried?
– MBaz
Commented Feb 7, 2023 at 23:02
• I was looking into irrational transfer functions , and I could not find any refrence. I have not tried anything since I have no idea where to start Commented Feb 7, 2023 at 23:05
• The Bode plot is the magnitude and phase of H(s) as you limit s to be the $j\omega$ axis. So as long as you can compute a magnitude and phase of the function, you can plot it! Commented Feb 7, 2023 at 23:59

If that's a problem for you, I recommend taking a basic Matlab class first.

%% plot a transfer function
% frequency axis
omega = logspace(-2,2,1000)';
% calculate the trasnfer function
H = 1./cosh(sqrt(1i*omega/10));

% and plot it
clf;
subplot(2,1,1);
semilogx(omega,10*log10(H.*conj(H)));
grid on;
ylabel('Level in dB');