# Obtaining a transfer function using two-port network analysis

Discussion in 'Electronics Homework Help' started by DaveyD, Mar 5, 2015.

1. ### DaveyD

5
0
Mar 5, 2015
Hello to all,

I have a 1st order passive band pass filter and I have been asked to obtain a transfer function using two-port network theory. Now I have asked two of my lecturers if this is possible, one said yes and the other said no. I am really confused.

Is it possible to obtain a transfer function using two-port network analysis?

If it is possible, what parameters are best to use, ie z,y,a,b,h or g?

Do you have any pointers, steps or a method I could follow?

The filter I designed is very simple and uses only resistors and capacitors. (Of course it doesn't do a very good job, infact the cutOff at -3dB is maintained throughout the small pass band range. This isn't my preferable choice of filter, but unfortunately this is what I have been told to do).

Here it is in all it's glory:

Vin --- high pass stage --- low pass stage ---Vout

Vin------C1------------R2------Vout
. . . . . . . . . | . . . . . . . | . . . . .
. . . . . . . . R1 . . . . . . C2 . . . .
. . . . . . . . . | . . . . . . . | . . . . .
. . . . . . . .GND . . . . GND . . .

A good book, website or/and info here would be really helpful. The information I have come across doesn't really relate two-port network theory directly to obtaining a transfer function from a simple cascaded filter network.

Kind Regards

Dave

2. ### Ratch

1,088
331
Mar 10, 2013
You can find the transfer function by loop analysis, node analysis, branch analysis, or the potentiometer method. Do you know how to do any of those? Usually the potentiometer method is the easiest. If R1=R2 and C1=C2, the analysis is greatly simplified.

Ratch

3. ### DaveyD

5
0
Mar 5, 2015
Hi thanks for the reply, I know of many other methods to obtain the transfer function in the s domain, I know of superposition, mesh, nodal, thevenin's, laplace, fourier. But the objective was to use two port network analysis, using either the z, y, a,b g,h parameters. Am i missing a connection here between, e.g nodal and two-port network theory?