Rational Fitting and Time Domain Analysis

Fit frequency domain data to rational function, calculate time, step, impulse, and frequency response

Use the rationalfit function to fit data defined in the frequency domain with an equivalent Laplace transfer function. Using rational function fitting you can create simple models for a required accuracy, model order reduction, zero phase on extrapolation to DC, and causal modeling system among other advantages.

Objects

`rational`	Perform rational fitting to complex frequency-dependent data
`rfmodel.rational`	Store output power and phase information for amplifiers or mixers

Functions

`rationalfit`	Perform rationalfit on an S-parameters object
`timeresp`	Time response for rational object and `rationalfit` function object
`stepresp`	Step-signal response of rational object and `rationalfit` function object
`freqresp`	Frequency response of rational object and `rationalfit` function object
`impulse`	Impulse response for rational function object
`ispassive`	Return true if `rationalfit` output is passive at all frequencies
`makepassive`	Enforce passivity of `rationalfit` output or a rational object
`passivity`	Plot passivity of N-by-N `rationalfit` function output
`generateSPICE`	Generate SPICE file from `rationalfit` of S-parameters

Topics

RF Model Objects

Describes the available RF model objects and their uses.

Featured Examples

Using Rational Object to Fit S-parameters

Use the rational object to create a rational fit to S-parameter data, and the various properties and methods that are included in the rational object.

Open Live Script

Passivity: Test, Visualize, and Enforce Passivity of rationalfit Output

Test, visualize, and enforce the passivity of output from the rationalfit function.

Open Live Script

Using 'NPoles' Parameter With rationalfit

Use the 'NPoles' parameter to improve the quality of the output of rationalfit. By default, the rationalfit function uses 48 or fewer poles to find the rational function that best matches the data. If 48 poles is not enough, it may be advantageous to change the range of the number of poles used by rationalfit.

Open Live Script

Using 'Weight' Parameter With rationalfit

Use the 'Weight' parameter to improve the quality of the output of rationalfit. By default, the rationalfit function minimizes the absolute error between the data and the rational function, treating all data points equally. When it is useful to emphasize some of the data points more than the others, use the 'Weight' parameter.

Open Live Script