Cascading Networks - Scattering Transfer parameters

Question asked by partha175 on Dec 22, 2008
Latest reply on Jan 8, 2009 by Dr_joel
Hello All

Page 14 of Agilent Application Note - AN154 - 'S-Parameter Design',     Clearly specifies the equations to compute 'Scattering Transfer
parameters'  from S-parameters.
Cascading of the two 2-port networks are is achieved by
multiplying the two 'Transfer parameters'  matrices.

I need to cascade two 2-port networks - Differential
measurement, that is for each network I have the following information
[ S11dd   S12dd   S11dc   S12dc
S21dd   S22dd   S21dc   S22dc
S11cd   S12cd   S11cc   S12cc
S21cd   S22cd   S21cc   S22cc ].

How do we cascade two such networks??

The following method is what I plan to use -  Please ascertain this

From the given 4x4 matrix, create four 2x2 matrices, each one
having information about 'dd', 'dc' , 'cd' and 'cc' respectively. That
is, the following four 2x2 matrices results
(1)         [ S11dd S12dd
S21dd S22dd]

(2)     [ S11dc S12dc
S21dc S22dc]
and so on...

Now for each of these 2x2 matrices, compute the 'Scattering Transfer
parameters' . Let us call these M1,M2, M3 and M4
Similarly, compute the 'Scattering Transfer parameters'  for the
second network. Let us call these N1,N2, N3 and N4.

Multiply the corresponding matrices to get the cascaded network.:
P1 = M1 * N1;
P2 = M2 * N2; and so on...

Can I hope to get a meaningful result with this method?