rfckt.txline class

Package: rfckt

General transmission line


h = rfckt.txline
h = rfckt.txline('Property1',value1,'Property2',value2,...)


Use the txline class to represent transmission lines that are characterized by line loss, line length, stub type, and termination.

h = rfckt.txline returns a transmission line object whose properties are set to their default values.

h = rfckt.txline('Property1',value1,'Property2',value2,...) returns a transmission line object, h, with the specified properties. Properties that you do not specify retain their default values.


AnalyzedResultComputed S-parameters, noise figure, OIP3, and group delay values
FreqFrequency data
IntpTypeInterpolation method
LineLengthTransmission line length
LossTransmission line loss
NameObject name
nPortNumber of ports
PVPhase velocity
StubModeType of stub
TerminationStub transmission line termination
Z0Characteristic impedance


analyzeAnalyze circuit object in frequency domain
calculateCalculate specified parameters for circuit object
circleDraw circles on Smith chart
getz0Characteristic impedance of transmission line object
listformatList valid formats for specified circuit object parameter
listparamList valid parameters for specified circuit object
loglogPlot specified circuit object parameters using log-log scale
plotPlot specified circuit object parameters on X-Y plane
plotyyPlot specified object parameters with y-axes on both left and right sides
polarPlot specified circuit object parameters on polar coordinates
semilogxPlot specified circuit object parameters using log scale for x-axis
semilogyPlot specified circuit object parameters using log scale for x-axis
smithPlot specified circuit object parameters on Smith chart
writeWrite RF data from circuit or data object to file


Frequency Domain Analysis of a Transmission Line

Construct a general transmission line, trl, with the default characteristic impedance of 50 ohms, phase velocity of 299792458 meters per second, and line length of 0.01 meters. Then perform frequency domain analysis from 1.0 GHz to 3.0 GHz. Plot the resulting S21 network parameters, using the 'angle' format, on the X-Y plane.

trl = rfckt.txline('Z0',75)
trl = 

   rfckt.txline with properties:

        LineLength: 0.0100
          StubMode: 'NotAStub'
       Termination: 'NotApplicable'
              Freq: 1.0000e+09
                Z0: 75
                PV: 299792458
              Loss: 0
          IntpType: 'Linear'
             nPort: 2
    AnalyzedResult: []
              Name: 'Transmission Line'

f = [1e9:1.0e7:3e9];     % Simulation frequencies
analyze(trl,f);          % Do frequency domain analysis
plot(trl,'s21','angle'); % Plot magnitude of S21


Ludwig, R. and P. Bretchko, RF Circuit Design: Theory and Applications, Prentice-Hall, 2000.

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