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coplanarWaveguide

Create coplanar waveguide transmission line

Since R2021b

Description

Use the coplanarWaveguide object to create a coplanar waveguide transmission line. A Coplanar waveguide is a common type of transmission line used in any PCB implementation of RF and microwave components. A coplanar waveguide transmission line has a center conductor strip and two ground planes. One ground plane is the layer that acts as the conductor strip and the other ground plane is the bottom layer.

Note

This PCB object supports behavioral modeling. For more information, see Behavioral Models. To analyze the behavioral model for a coplanar waveguide, set the Behavioral property in the sparameters function to true or 1

Three part image from right to left: Default image of a coplanar waveguide. Current distribution on the coplanar waveguide. S-parameters plot of the coplanar waveguide.

Creation

Description

cpgw = coplanarWaveguide creates a default coplanar waveguide transmission line with a Teflon substrate and default property values for a 50 ohm transmission line.

example

cpgw = coplanarWaveguide(Name=Value) sets Properties using one or more name-value arguments. For example, coplanarWaveguide(Width=0.0047) creates a coplanar waveguide transmission line of width 0.0047 meters. Properties not specified retain their default values.

Properties

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Length of the coplanar waveguide transmission line in meters, specified as a positive scalar.

Example: cpgw = coplanarWaveguide(Length=0.0300)

Data Types: double

Width of the coplanar waveguide transmission line in meters, specified as a positive scalar.

Example: cpgw = coplanarWaveguide(Width=0.0047)

Data Types: double

Distance between the transmission line and the adjacent top layer metal of the ground plane, specified as a positive scalar in meters.

Example: cpgw = coplanarWaveguide(Spacing=3.0000e-04)

Data Types: double

Distance between the vias in meters, specified as a two-element vector of positive elements.

Example: cpgw = coplanarWaveguide(ViaSpacing=[0.0021 0.0060])

Data Types: double

Diameter of the via in meters, specified as a positive scalar.

Example: cpgw = coplanarWaveguide(ViaDiameter=7.0000e-04)

Data Types: double

Height of the coplanar waveguide transmission line from the ground plane, specified as a positive scalar in meters.

Example: cpgw = coplanarWaveguide(Height=0.0020)

Data Types: double

Width of the ground plane in meters, specified as a positive scalar.

Example: cpgw = coplanarWaveguide(GroundPlaneWidth=0.0350)

Data Types: double

Type of dielectric material used as a substrate, specified as a dielectric object. The dielectric material in a coplanarWaveguide object with default properties is Teflon.

Example: d = dielectric("FR4"); cpgw = coplanarWaveguide(Substrate=d)

Data Types: string | char

Type of metal used in the conducting layers, specified as a metal object. The type of metal in a coplanarWaveguide object with default properties is PEC.

Example: m = metal("Copper"); cpgw =coplanarWaveguide(Conductor=m)

Data Types: string | char

Flag to add a metal shielding to the PCB component, specified as a logical 0 or logical 1. The default value is logical 0.

Example: IsShielded = true or 1 add a metal shield.

Note

To enable FEM solver required for the metal shield property, download the Integro-Differential Modeling Framework for MATLAB. To download this add-on:

  1. In the Home tab Environment section, click on Add-Ons. This opens the add-on explorer. You need an active internet connection to download the add-on.

  2. Search for Integro-Differential Modeling Framework for MATLAB and click Install.

  3. To verify if the download is successful, run

    matlab.addons.installedAddons
    in your MATLAB® session command line.

  4. On Windows, to run the IDMF add-on, you must install the Windows Subsystem for Linux (WSL). To install WSL, see Install Linux on Windows with WSL.

    The Windows Defender Firewall can block the PostgreSQL server when using the IDMF add-on. To resolve this issue, you can allow the server to communicate on desired networks if the firewall prompts. Alternatively, you can manually add the executable file of the PostgreSQL server located in <matlabroot>\sys\postgresql\win64\PostgreSQL\bin\postgres.exe. For more information, see https://support.microsoft.com/en-us/windows/risks-of-allowing-apps-through-windows-defender-firewall-654559af-3f54-3dcf-349f-71ccd90bcc5c.

Data Types: logical

This property is read-only.

Metal shield for the PCB component, specified as a shape.Box object. The length and width of the box must be equal to the length and width of the ground plane. The center of the box is at [0 0 Shielding.Height].

Dependencies

To enable the Shielding property, set the IsShielded property to true or 1.

Type of RF connector assembled at the feed locations of the PCB component, specified as a RFConnector object.

Example: Create connector from RFConnector object like this: coaxial = RFConnector adds a coaxial connector.

Dependencies

To enable the Connector property, set the IsShielded property to true or 1.

Object Functions

chargeCalculate and plot charge distribution
currentCalculate and plot current distribution
designDesign coplanar waveguide transmission line around particular frequency
feedCurrentCalculate current at feed port
getZ0Calculate characteristic impedance of transmission line
meshChange and view mesh properties of metal or dielectric in PCB component
shapesExtract all metal layer shapes of PCB component
showDisplay PCB component structure or PCB shape
sparametersCalculate S-parameters for RF PCB objects
RFConnectorCreate RF connector

Examples

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Create a coplanar waveguide transmission line.

waveguide = coplanarWaveguide
waveguide = 
  coplanarWaveguide with properties:

              Length: 0.0231
               Width: 0.0039
             Spacing: 2.0000e-04
          ViaSpacing: [0.0011 0.0070]
         ViaDiameter: 5.0000e-04
              Height: 0.0016
    GroundPlaneWidth: 0.0300
           Substrate: [1x1 dielectric]
           Conductor: [1x1 metal]
          SolverType: 'MoM'
          IsShielded: 0

View the coplanar waveguide transmission line.

show(waveguide)

Figure contains an axes object. The axes object with title coplanarWaveguide element, xlabel x (mm), ylabel y (mm) contains 48 objects of type patch, surface. These objects represent PEC, feed, Teflon.

Calculate the S-parameters of the waveguide from 1-10 GHz.

sparam = sparameters(waveguide,1e9:0.3e9:10e9)
sparam = 
  sparameters with properties:

      Impedance: 50
       NumPorts: 2
     Parameters: [2x2x31 double]
    Frequencies: [31x1 double]

Plot the S-parameters.

rfplot(sparam)

Figure contains an axes object. The axes object with xlabel Frequency (GHz), ylabel Magnitude (dB) contains 4 objects of type line. These objects represent dB(S_{11}), dB(S_{21}), dB(S_{12}), dB(S_{22}).

Create a coplanar waveguide transmission line using a gold substrate as the dielectric.

txem = coplanarWaveguide;
txem.Conductor = metal("Gold");

Design the coplanar waveguide at a frequency of 3 GHz, line length of 0.5 meters, and impedance of 75 ohms.

txem = design(txem,3e9,LineLength=0.5,Z0=75);
show(txem)

Figure contains an axes object. The axes object with title coplanarWaveguide element, xlabel x (mm), ylabel y (mm) contains 72 objects of type patch, surface. These objects represent Gold, feed, Teflon.

Compute and plot the behavioral S-parameters of the waveguide.

spar = sparameters(txem,3e9,Behavioral=true);
rfplot(spar)

Figure contains an axes object. The axes object with xlabel Frequency (GHz), ylabel Magnitude (dB) contains 4 objects of type line. These objects represent dB(S_{11}), dB(S_{21}), dB(S_{12}), dB(S_{22}).

References

[1] Pozar, David M. Microwave Engineering. 4th ed. Hoboken, NJ: Wiley, 2012.

Version History

Introduced in R2021b

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