I am trying to plot the frequency response of a transfer function without the use of tf and bode.

I have a transfer function in the s domain for which I have calculated the elements needed for the frequency response and have sketched the plot so I know how it should look. I have calculated the j-omega component. I could easily use tf and bode and get the plot but the challenge is that I cant use those functions and must accept a vector of frequencies for which to plot this. Just wanted to know a good approach to tackling this and achieving the same plot.

Answer 1

[Birdman]

One way to do it is symbolically. Change the transfer function and see the results:

syms s
Gs=1/(s+1);
x=logspace(-2,2);
GsF=vpa(subs(Gs,s,x*1i),3);
GsFAbs=abs(GsF);
GsFMag=20*log10(GsFAbs);
subplot(2,1,1);
semilogx(x,GsFMag);xlabel('Frequency(rad/sec)');ylabel('Magnitude(dB)');title("Frequency response for "+string(Gs))
set(gca,'XLim',[0 max(x)]);
subplot(2,1,2);
GsFPh=angle(GsF)*180/pi;
semilogx(x,GsFPh);xlabel('Frequency(rad/sec)');ylabel('Phase(deg)');
set(gca,'XLim',[0 max(x)]);