How to add lossless txline to each port of 4-port sparameters and save in new touchstone file?

Hello, I am a novice to matlab scripting. I'm having trouble adding 4 lossless transmission lines to each port of an imported 4-port s-parameters and saving to a new touchstone file. I was able to create a single transmission line and plot S21 and angle per the help, but I get stuck after that. Thanks in advance.

Answer 1

[Balavignesh]

Hi BSimono,

As per my understanding, you would like to add 4 lossless transmission lines to each port of an imported 4-port 'S-parameters'.

I would suggest you load the 4-port S-parameters using the 'sparameters' function and define the characteristics of the lossless transmission lines such as 'line_length' and 'line_z0' that you would want to add to each port.

You could use 'rfkct.txline' object to create the transmission line models and you could iterate over each port of the 'S-parameters' to add the transmission models by creating an empty cascade object using the 'rfckt.cascade' function.

You could save the modified S-parameters to a new Touchstone file using the 'write' function.

The following code may help you achieve this:

% Load the original S-parameters file
    % original_sparams = sparameters('filename');

% Define the transmission line parameters
line_length = 0.1; % Length of the transmission line (in meters)
line_Z0 = 50; % Characteristic impedance of the transmission line (in Ohms)

% Create the transmission line model
transmission_line = rfckt.txline('LineLength', line_length, 'Z0', line_Z0);

% Create an empty cascade object
modified_sparams = rfckt.cascade;

% Add the transmission line to each port of the cascade using a 'for' loop
    % for port = 1:4
    %     modified_sparams.Elements{end+1} = transmission_line;
    % end

% Connect the original S-parameters to the cascade
    % modified_sparams.Elements{end+1} = original_sparams;

% Save the modified S-parameters to a new Touchstone file using 'write'

Kindly refer to the following documentation links to have more information on:

• 'rfckt.txline' object: https://www.mathworks.com/help/rf/ref/rfckt.rfckt.txline.html
• 'rfckt.cascade' object: https://www.mathworks.com/help/rf/ref/rfckt.rfckt.cascade.html
• 'sparameters' function: https://www.mathworks.com/help/rf/ref/sparameters.html

Hope that helps !

Balavignesh

[BSimono]

Hi Balavignesh,

Thank you for your help. I did manage to find a solution since posting last year, but this seems more elegant!