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rfckt.coaxial

RF Amplifier

Description

Use the coaxial class to represent coaxial transmission lines that are characterized by line dimensions, stub type, and termination.

Use the coaxial class to represent coaxial transmission lines that are characterized by line dimensions, stub type, and termination.

A coaxial transmission line is shown in cross-section in the following figure. Its physical characteristics include the radius of the inner conductor of the coaxial transmission line a, and the radius of the outer conductor b.

Creation

Syntax

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

Description

example

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

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

Properties

expand all

Computed S-parameters, noise figure, OIP3, and group delay values, specified as an rfdata.data object. This is a read-only property. For more information refer, .

Data Types: function_handle

Relative permittivity of dielectric, specified as a scalar. The relative permittivity is the ratio of permittivity of the dielectric,ε, to the permittivity in free space, ε0. The default value is2.3.

Data Types: double

Inner conductor radius, specified as a scalar in meters. The default value is 7.25e-4.

Data Types: double

Physical length of transmission line, specified as a scalar in meters. The default value is 0.01.

Data Types: double

Tangent of loss angle of dielectric, specified as a scalar. The default value is 0.

Data Types: double

Relative permeability of dielectric, specified as a scalar. The ratio of permeability of dielectric, μ, to the permeability in free space, μ0. The default value is 1.

Data Types: double

Object name, specified as a 1-by-N character array. This is a read-only property.

Data Types: char

Number of ports, specified as a positive integer.

Data Types: double

Outer conductor radius, specified as a scalar in meters. The default value is 0.0026.

Data Types: double

Conductor conductivity, specified as a scalar in Siemens per meter (S/m). The default value is Inf.

Data Types: double

Type of stub, specified as one of the following values: 'NotaStub', 'Series', 'Shunt'.

Data Types: double

Stub transmission line termination, specified as one of the following values: 'NotaStub', 'Series', 'Shunt'.

Data Types: double

Object Functions

analyzeAnalyze circuit object in frequency domain
calculateCalculate specified parameters for circuit object
circleDraw circles on Smith chart
listformatList valid formats for specified circuit object parameter
getz0Characteristic impedance of transmission line object
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 y-axis
smithPlot specified circuit object parameters on Smith chart
writeWrite RF data from circuit or data object to file

Examples

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Create a coaxial transmission line with 0.0045 meters outer radius using rfckt.coaxial.

tx1=rfckt.coaxial('OuterRadius',0.0045)
tx1 = 

   rfckt.coaxial with properties:

       OuterRadius: 0.0045
       InnerRadius: 7.2500e-04
               MuR: 1
          EpsilonR: 2.3000
       LossTangent: 0
         SigmaCond: Inf
        LineLength: 0.0100
          StubMode: 'NotAStub'
       Termination: 'NotApplicable'
             nPort: 2
    AnalyzedResult: []
              Name: 'Coaxial Transmission Line'

Algorithms

The analyze method treats the transmission line as a 2-port linear network. It computes the AnalyzedResult property of a stub or as a stubless line using the data stored in the rfckt.coaxial object properties as follows:

  • If you model the transmission line as a stubless line, the analyze method first calculates the ABCD-parameters at each frequency contained in the modeling frequencies vector. It then uses the abcd2s function to convert the ABCD-parameters to S-parameters.

    The analyze method calculates the ABCD-parameters using the physical length of the transmission line, d, and the complex propagation constant, k, using the following equations:

    A=ekd+ekd2B=Z0*(ekdekd)2C=ekdekd2*Z0D=ekd+ekd2

    Z0 and k are vectors whose elements correspond to the elements of f, the vector of frequencies specified in the analyze input argument freq. Both can be expressed in terms of the resistance (R), inductance (L), conductance (G), and capacitance (C) per unit length (meters) as follows:

    Z0=R+j2πfLG+j2πfCk=kr+jki=(R+j2πfL)(G+j2πFC)

    where

    R=12πσcondδcond(1a+1b)L=μ2πln(ba)G=2πωεln(ba)C=2πεln(ba)

    In these equations:

    • a is the radius of the inner conductor.

    • b is the radius of the outer conductor.

    • σcond is the conductivity in the conductor.

    • μ is the permeability of the dielectric.

    • ε is the permittivity of the dielectric.

    • ε″ is the imaginary part of ε, ε″  = ε0εrtan δ, where:

      • ε0 is the permittivity of free space.

      • εr is the EpsilonR property value.

      • tan δ is the LossTangent property value.

    • δcond is the skin depth of the conductor, which the method calculates as 1/πfμσcond.

    • f is a vector of modeling frequencies determined by the Outport block.

  • If you model the transmission line as a shunt or series stub, the analyze method first calculates the ABCD-parameters at the specified frequencies. It then uses the abcd2s function to convert the ABCD-parameters to S-parameters.

    When you set the StubMode property to 'Shunt', the 2-port network consists of a stub transmission line that you can terminate with either a short circuit or an open circuit as shown in the following figure.

    Zin is the input impedance of the shunt circuit. The ABCD-parameters for the shunt stub are calculated as:

    A=1B=0C=1/ZinD=1

    When you set the StubMode property to 'Series', the 2-port network consists of a series transmission line that you can terminate with either a short circuit or an open circuit as shown in the following figure.

    Zin is the input impedance of the series circuit. The ABCD-parameters for the series stub are calculated as

    A=1B=ZinC=0D=1

References

[1] Pozar, David M. Microwave Engineering, John Wiley & Sons, Inc., 2005.

Introduced before R2006a

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