RF Toolbox™ 2.3

Product Description

• RF Toolbox Key Features
• Defining RF Components
• Designing Networks
• Modeling with Rational Functions
• Converting Network Parameters
• Visualizing Component and Network Behavior

Modeling with Rational Functions

You can use RF Toolbox to model single-ended and differential high-speed transmission lines using rational functions. This type of model is useful in signal integrity engineering, where the goal is the reliable connection of high-speed semiconductor devices using, for example, backplanes and printed circuit boards.

Rational function fitting provides the following advantages over traditional techniques, such as inverse fast Fourier transform:

• Simpler models for a given accuracy
• Model order reduction, letting you trade off complexity and accuracy
• Zero phase on extrapolation to DC, avoiding the need to write elaborate constraint algorithms
• Physical correspondence between the model and transmission line characteristics, providing greater insight

In the typical signal integrity workflow, you use RF Toolbox after you characterize the backplane with 4-port network parameters and before you begin the design of the high-speed semiconductor I/O circuitry. Specifically, you:

• Measure the network parameters with a vector network analyzer
• Import the Touchstone data file
• Convert the single-ended 4-port S-parameters to 2-port differential S-parameters
• Compute the transfer function
• Fit the transfer function to a closed-form rational function model, reducing the order as needed
• Export the model to Simulink or in Verilog-A format for use as a test environment in the SPICE-like analog circuit simulator, which you use to design the I/O circuitry

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