MATLAB: 4-Port Scatter parameters to 2-Port Scatter Paremeters

2-port4-portRF Toolboxs-parameters

Is it always customary to convert 4-Port S-Parameters to 2-Port S-Parameters and then plot Smith's chart ? Why ?

Best Answer

Dear Jay,

Converting S-parameters can be done, but it is not compulsory. I can imagine that you might want to do it when you are interested only in a pair of ports (e.g. selecting a certain channel in multi-port measurements, and terminate all the other ports with a certain impedance), or if you want to translate single ended measurements to differential data. Plotting on a smith chart is then done to visualize the input or the output port behaviour.

With best regards,

Giorgia

Related Solutions

MATLAB: Can a complete 4-port S-parameter (including differential and common mode) simulation of a RF broadband system be done using the RF Toolbox 2.5 (R2009a)

This can be done using the RF Toolbox 2.5 (R2009a). The following functions can be used to realize this application.

S2MM - Convert 4N-port single-ended S-parameters to 4 2N-port mixed-mode S-parameters.

SMM2s - Convert 4 2N-port mixed-mode S-parameters to single-ended S-parameters.

S2DD - Convert 4-port S-parameters to differential 2-port S-parameters Sdd.

S2DC - Convert 4-port S-parameters to cross mode 2-port S-parameters Sdc.

S2SCD - Convert 4-port S-parameters to cross mode 2-port S-parameters Scd.

S2SCC - Convert 4-port S-parameters to common mode 2-port S-parameters Scc.

S2TF - Calculate transfer function from 2-port S-parameters.

In order to model mixed-mode simulation, there might be multiple approaches to go about it.

The RF Toolbox documentation includes an example "Modeling a High-Speed Backplane (Part 2: 4-Port S-Parameters to a Rational Function Model)" showing a differential-model application.

If you replace S2SDD with S2SCC, you will get the common-mode. Please note that when using S2TF, the impedances are different for differential-mod and common-mode:

 Zs(common-mode) = (Zs1 * Zs2)/(Zs1 + Zs2)
 Zl(common-mode) = (Zl1 * Zl2)/(Zl1 + Zl2)
 Z0(common-mode) = Z0/2

vs.

 Zs(differential-mode) = Zs1 + Zs2
 Zl(differential -mode) = Zl1 + Zl2
 Z0(differential -mode) = 2*Z0

MATLAB: How to cascade N-port S-parameters using the RF Toolbox

This enhancement has been incorporated in Release 2007b (R2007b). For previous product releases, read below for any possible workarounds:

The ability to cascade N-port S-parameters is not available in RF Toolbox. RF Toolbox only supports cascading of two port networks only.

However, RF Toolbox does allow reading and writing of N-port data files, but any analysis routines of this data must be provided by the user.

The following is an example of writing and reading N-port S-parameter files.

nports=42;
h=rfckt.passive
h.NetworkData.Freq = [1;2]*1e9
h.NetworkData.Data = cat(3,rand(nports,nports)+j*rand(nports,nports),rand(nports,nports)+j*rand(nports,nports))
analyze(h,h.NetworkData.Freq)
write(h,['test.s' num2str(nports) 'p'])
h2=read(rfckt.passive, ['test.s' num2str(nports) 'p'])

Best Answer

Related Solutions

MATLAB: Can a complete 4-port S-parameter (including differential and common mode) simulation of a RF broadband system be done using the RF Toolbox 2.5 (R2009a)

MATLAB: How to cascade N-port S-parameters using the RF Toolbox

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