frequency transformation bp2lp

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franticET

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hi i've to design a bandpass active filter of 6th order PRB type, but i've a problem in the design procedure.
In order to obtain the desired filter i need to convert the bandpass transfer function in a lowpass transfer function.
I've found this example:

[LATEX]H(s)=K0*\frac{B0 + B1*T(s) + B2*T^2(s) + B3*T^3(s)}{1 + F2*T^2(s) + F3*T^3(s)}[/LATEX]

where
[LATEX]T(s)=\frac{k}{k+s}[/LATEX]

F2 and F3 are feedback resistors and Bs the output of each block T(s)

The next step is the result of the BP to LP transformation
[LATEX]H(s)=m\frac{b0}{a0}*\frac{b3*s^3 + b2*s^2 + b1*s + b0}{s^3 + a2*s^2 + a1*s + a0}[/LATEX]

this was performed in matlab but i can't reach this result also applyng the conversion
[LATEX]s=>Q*\frac{s^2+1}{s}[/LATEX]

Anyone could help me please?
What are the steps used in this example to obtain H(s)?
Thanks a lot
 
i's say factor your terms and then you can move all poles and zeroes until you get bode plot you like.
 
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