rfmodel.rational class - Package: rfmodel

Rational function model

Syntax

Description

Use the rational class to represent RF components using a rational function model of the form

There are two ways to construct an rfmodel.rational object:

• You can fit a rational function model to the component data using the rationalfit function.

• You can use the rfmodel.rational constructor to specify the pole-residue representation of the component directly.

h = rfmodel.rational returns a rational function model object whose properties are set to their default values.

h = rfmodel.rational('Property1',value1,'Property2',value2,...) returns a rational function model object, h, with the specified properties. Properties that you do not specify retain their default values.

Properties

A	Poles of rational function
C	Residues of rational function
D	Frequency response offset
Delay	Frequency response time delay
Name	Object name

Methods

freqresp	Frequency response of model object
ispassive	Check passivity of scalar model object
stepresp	Step-signal response of model object
timeresp	Time response for model object
writeva	Write Verilog-A description of RF model object

Examples

Fit a rational function to data from an rfdata.data object:

orig_data=read(rfdata.data,'default.s2p');
freq=orig_data.Freq;
data=orig_data.S_Parameters(2,1,:);
fit_data=rationalfit(freq,data)

fit_data =
 
     Name: 'Rational Function'
     A: [2x1 double]
     C: [2x1 double]
     D: 0
     Delay: 0

Define, evaluate, and visualize a rational function in three steps:

• Construct a rational function model, rat, with poles at -4 Mrad/s, -3 Grad/s, and -5 Grad/s and residues of 600 Mrad/s, 2 Grad/s and 4 Grad/s.

• Perform frequency-domain analysis from 1.0 MHz to 3.0 GHz.

• Plot the resulting frequency response in decibels on the X-Y plane.

rat=rfmodel.rational...
     ('A',[-5e9,-3e9,-4e6],...
      'C',[6e8,2e9,4e9]);      % Create model
f = [1e6:1.0e7:3e9];
[resp,freq]=freqresp(rat,f);   % Compute frequency response
figure
 plot(freq/1e9,db(resp));      % Plot frequency response
 xlabel('Frequency (GHz)')
 ylabel('Magnitude (dB)')

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