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Compute Active S-Parameters | XFdtd

Activate multiple ports for S-parameter analysis.

The Compute Active S-Parameters macro computes S-parameters when all ports are active in a multi-port system. Active S-parameters differ from the passive results of a single active port, and enable analysis when utilizing beam steering, phased arrays, or multiple antenna elements operating simultaneously that are involved in a myriad of applications.


Prior to computing active S-parameters, passive S-parameters must be computed and input to a schematic.

Users must complete the following steps prior to running the macro:

  1. Add an antenna with multiple elements to the project.
  2. Set up multiple circuit components in order to feed each element.
  3. Create an FDTD simulation with S-parameters enabled.
  4. Run the simulation for passive S-parameter results and the full S-parameter matrix.
  5. Create a schematic and add an FDTD block containing the simulation's S-parameter matrix.
  6. Connect a voltage source for each of the ports, either specifying a phase shift if desired or adding components—such as inductors, capacitors, and phase shifters—as needed to build the topology.


After meeting the prerequisites, run the macro by following these steps:

  1. Download the Compute Active S-Parameters.xmacro
  2. Place the file in your Macros Menu directory, or right-click on Scripts in the Project Tree and choose Import Scripts.

Once the script is available, select the results for which to compute active S-parameters.

  1. In the Project Tree, select the schematic relevant to the S-parameter calculation and execute the script by selecting it in the Macros Menu and clicking the Execute Macro button in the Scripting window.

The script's dialog window opens, allowing users to select which results to view. Operating modes are often used to specify different beam states in phased array applications.

  1. Under the Operating Modes tab, select the operating modes for which to calculate active S-parameters.

Users can choose from the listed operating modes, or use the All or None buttons to either include or omit all of the schematic's operating modes, respectively.

  1. Under the Matrix tab, select the active S-parameter results to compute.

The Diagonal button identifies the components of interest as those appearing diagonally in the matrix. The All and None buttons either include or omit every component in the matrix, respectively.

  1. Under the Output tab, define the result-graph relationship.

Users can choose from two options:

When including the output in one graph, users can either create a New Graph or add the results to an existing Target Graph, when applicable.