Welcome to this first part of The MathWorks webinar
technical series regarding S-parameter analysis
using MATLAB.
In this installment, basic s-parameter analysis
is performed where S-parameter data is imported
and plotted on both rectangular and polar plots.
Finally, you will be shown how to write S-parameter data
to a touchstone data file.
Let's begin by getting familiar with the functions that
are going to be used today.
Namely, S-parameters, rfplot, smith, and rfwrite.
Help for each of these RF toolbox functions
can be found by typing in Help and the function
name at the MATLAB command prompt,
or typing in the function name in the Help browser.
Remembering all the various MATLAB
function names can be burdensome.
And I recommend that instead of memorizing all the names,
that you refer to product examples
to recall the use of these functions.
A couple of RF toolbox examples that I would recommend
include the following.
First, modeling a high-speed backplane.
This example readily shows the user
how to import as parameters into MATLAB,
manipulate the various as parameter objects,
and finally, how to easily plot the S-parameter response
on a rectangular plot.
Second, writing the touchstone file.
This second example is a good reference example
for saving S-parameter data into a multi port touchstone data
file, and provides a workflow example
that can be easily followed.
Now let's go through an example of doing all of this.
First, let us import the data from a 4 port S-parameter data
file and assign it to a MATLAB data object.
Let's call it s4p.
Type in s4p = sparameters default .s4p.
Notice that there are properties for frequency, impedance,
the S-parameters, and the number of ports that the file has.
Let's now plot the magnitude response
for elements 1,1 and 2,1 of this S-parameter object.
First, open a new figure.
Then use the RF plot function that
calls the S-parameter object as well as the matrix element
that is to be plotted.
To plot on the same figure, invoke the Hold command,
and then plot the next S-parameter element
that you want to visualize.
To view the phase response, the process
is very similar, except you need to add the plot flag
angle into the RF plot to view this figure.
Start by opening a new figure, use the RF plot function,
but add the Angle plot flag, and finally turn on the grid.
In a similar fashion, diagonal elements
at the S-parameter data can be plotted on a Smith chart.
To do this, use the Smith function.
Again, let's add a new figure, and then plot
the response of element 2,2.
For the final part of today's session,
let's create a new S-parameter data
file that only contains the data of s4p to 10 gigahertz.
The process to do this from the MATLAB command window
is straightforward.
First, assign a file name of your new S-parameter file
to a MATLAB variable.
Let's use filename = new_s4p_data.s4p.
Next, you will need to determine the frequency vector index
value that corresponds to 10 gigahertz.
This is done by using the Find function.
Next, you would use the RF Write function
in the following manner.
First, call the S-parameter data to be written to the new data
file.
Then, call the frequency range associated with the data
and then include the file name.
Once executed, you can see the new data file has been
saved to my working directory.
I hope that you have found this video useful.
And next time we will be looking at using
MATLAB for concatenating arbitrary S parameter data sets
together.