Accurate S-Parameter Modeling with the AFS Platform

The AFS Platform is ideal for simulator circuits with complex S-parameter models. The platform provides >10M-element capacity and handles S-parameters with hundreds of ports.

S-parameters are used to model a component’s behavior in the frequency domain and are typically applied to passive components like baluns, spiral inductors, transmission lines, and package models. Circuit simulators require S-parameter data when designers want to include the component in the circuit verification. S-parameter files are usually generated by field solvers, or test and measurement equipment. Accurately modeling S-parameters for circuit simulation can be challenging.

With any simulator, using S-parameters raises potential accuracy issues. Simulators read the S-parameters file and fit the data to a model for use during simulation. It is important for designers to make sure the simulator produces a high quality fit to ensure accurate simulation results. The AFS WaveCrave waveform viewer provides a tandem mode interactive visual debugging capability that enables designers to plot the S-parameter fit against the original S-parameter data, as shown in the figure below.

If the fit is not accurate, designers can improve the fit by adding options to the resulting nport component in the netlist. Alternatively they can tune the S-parameter input data as follows:

• Select values at DC
• Expand the fitting frequency range
• Trim noisy data from the S-parameter file
• Add delay elements for long structures
• Change the number of poles for fitting

After making any changes, designers can again use the AFS WaveCrave waveform viewer to check the resulting fit.

For more information, contact your BDA application engineer or click here for a web request.