Computing with scattering parameters

Hi!

Does anybody know how to compute with S-parameters of an arbitrary network that consist of many elementary components connected to each other. I try to build my own simulation program.

Peter

Hi peter,

I am not sure that I fully understand your question, however you have two methods
1. using the transmission matrix: if the components are cascaded you can convert the s matrix of each component to the transmission matrix, and then simply multiply them.

2. If the components are not cascaded, or have more than two ports, you would have to use the definition of the S-matrix, i.e. you will have to find s11 as the reflected field/ incident field when all the other ports are matched. It would be difficult if you have a lot of components.

Here is one possible example (se attachment)
Goal: compute S11, S12, S13, S14 and S15

All parameters Sa, Sb, ... to Sh are known.

Peter

Hi;
I advise you to use a microwave simulation software or to use Matlab.

Hi peter,

I am sorry for being late, but I have been too busy the last few days. However, concerning your structure

a. Sa & Sb can be combined to be one s matrix (
e.g. multiplying the two transmission matrix)

b. now, we have a complicated strucutre and you will have to do it the hard way.

S11 = V1-/V1+ (- means reflected or in the outward direction, and + means incident or in the inward direction) when all the other ports are matched. so, we put a matched load on the ports P2 - P4, find the reflected wave at P1. One way to do this is the following, for networks Se, Sf, Sg, Sh find the reflection coefficient when the other side is matched., sa re,rf,rg,rh, rd = s11d. to determine the reflection coefficient at the input of Sc you have the following system

[V-] = *[V+]

and

V2+/V2- = re, V3+/V3- = rf, and so on.

using the above equations you can find V1-/V1+ i.e. the reflection coefficient at Sc. Again using this reflection coefficient, and with the same method used for Se-Sh find the reflection coefficient at port 1, i.e. S11.


Hope this might help,
Adel_48

adel_48 said:

Hi peter,

I am not sure that I fully understand your question, however you have two methods
1. using the transmission matrix: if the components are cascaded you can convert the s matrix of each component to the transmission matrix, and then simply multiply them.

2. If the components are not cascaded, or have more than two ports, you would have to use the definition of the S-matrix, i.e. you will have to find s11 as the reflected field/ incident field when all the other ports are matched. It would be difficult if you have a lot of components.

Click to expand...

hi~~
I'm interesting about transmission matrix method , but I don't know how to start

programming or coding , can you give me some example ??

thanks~~