How do I convert a transfer function of a low pass filter to bandpass?

I obtained the transfer function like this:

syms s;
N=4;
for k=1:N
    w=((2*k+N-1)/(2*N))*pi;
    Skr(k) = cos(w);
    Ski(k) = sin(w);
end
Sk=complex(Skr,Ski);
Sknum=prod(-Sk)
Skdem=(poly(Sk))
Hs=tf(Sknum, Skdem)

And now I need to replace s for the expression Op*(s^2+ Oi*Os)/s*BW, in where BW is the bandwith (Os- Oi)

I need help to find the new transfer function for the bandpass filter and to plot it like this:

%freqs(Sknum, Skdem);
%[Hs,w]=freqs(Sknum, Skdem);
%figure,
%plot(w, 20*log10(abs(Hs)))

Thanks!

[Rik]

Restored from Google cache.

Answer 1

[Star Strider]

If you want to use the Signal Processing Toolbox functions, this works:

syms s;
N=4;
for k=1:N
    w=((2*k+N-1)/(2*N))*pi;
    Skr(k) = cos(w);
    Ski(k) = sin(w);
end
Sk=complex(Skr,Ski);
Sknum=prod(-Sk)
Skdem=(poly(Sk))
Hs=tf(Sknum, Skdem)

figure
bode(Hs)

Hs_ss = ss(Hs);

Wo = 25;                                            % Centre Frequency
Bw = 10;                                            % Bandwidth
[At,Bt,Ct,Dt] = lp2bp(Hs_ss.A, Hs_ss.B, Hs_ss.C, Hs_ss.D, Wo, Bw);
Hs_ss_bp = ss(At,Bt,Ct,Dt);

figure
bode(Hs_ss_bp)

.