Simulink S-Parameters Plotting

I would would like to know how to plot the frequency response when two Simulink SimRF S-Parameters blocks are connected to each other. With a single block you can simply run the Plot function built within but now I have two blocks in series.

Answer 1

[Giorgia Zucchelli]

Dear Mark,

If you are using components from the Equivalent Baseband library, you can plot the S-parameters of the overall cascade of components using the visualization pane of the Output Port.

If you are using components from the Circuit Envelope library you need to build a simulation testbench to verify the S-parameters of the network under test. In terms of best practices, I would recommend to:

• Use "Time Domain Modeling" for the S-parameters. Verify that the rational fitting is sufficiently accurate.
• Use a relatively small simulation sample time in the SimRF parameters block (e.g. 4 or 8 times smaller than the envelope simulation bandwidth)
• Use a random number source to excite the chain with a wideband signal
• Use a Spectrum Analyzer to visualize the frequency domain output signals (e.g. S21, S11). An alternative is to use the "Baseband Transfer Function" block from the free Mixed-Signal Library that you can download from here: http://www.mathworks.com/mixed-signal-systems/
• Use an ideal coupler to probe the reflections at the input / output. You can build an ideal coupler using an S-parameters block with these [0 1 0;1 0 0;0 1 0] parameters.

With this approach you will be able to verify the behaviour of the overall network of S-parameters as it is simulated in the time domain. If you just need to inspect the S-parameters in the frequency domain, you can just use RF Toolbox functions, or refer to the SimRF shipping demo "AC Analysis of an RF System".

With best regards, Giorgia