coupledMicrostripLine

Create coupled microstrip transmission line

Since R2021b

Description

Use the coupledMicrostripLine object to create a coupled microstrip transmission line. Coupled microstrip transmission lines are used to design directional couplers and filters. The combination of even and odd mode impedances determines the coupling ratio between the direct arm and the coupled arm.

To analyze the behavioral model for the coupled microstrip line, set the Behavioral property in the sparameters to true or 1.

Creation

Syntax

coupledmicrostrip = coupledMicrostripLine

coupledmicrostrip = coupledMicrostripLine(Name=Value)

Description

coupledmicrostrip = coupledMicrostripLine creates a default coupled microstrip transmission line with a Teflon substrate and default properties for a resonating frequency of 1.5 GHz.

coupledmicrostrip = coupledMicrostripLine(Name=Value) sets Properties using one or more name-value arguments. For example, coupledMicrostripLine(Length=0.0300) creates a coupled microstrip transmission line of length 0.0300 meters.

Properties

Length — Length of coupled microstrip line

0.0271 (default) | positive scalar

Length of the coupled microstrip line in meters, specified as a positive scalar.

Example: coupledmicrostrip = coupledMicrostripLine(Length=0.0300)

Data Types: double

Width — Width of coupled microstrip line

0.0051 (default) | positive scalar

Width of the coupled microstrip line in meters, specified as a positive scalar.

Example: coupledmicrostrip = coupledMicrostripLine(Width=0.0041)

Data Types: double

Spacing — Distance between the direct arm and the coupled arm

0.0046 (default) | positive scalar

Distance between the direct arm and the coupled arm of the coupled microstrip transmission line, specified as a positive scalar in meters.

Example: coupledmicrostrip = coupledMicrostripLine(Spacing=0.00300)

Data Types: double

Height — Height of coupled microstrip line

0.0016 (default) | positive scalar

Height of the coupled microstrip line from the ground plane, specified as a positive scalar in meters. In the case of a multilayer substrate, use the Height property to create a coupled microstrip line at the interface of the two dielectrics.

Example: coupledmicrostrip = coupledMicrostripLine(Height=0.0023)

Data Types: double

GroundPlaneWidth — Width of ground plane

0.0300 (default) | positive scalar

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

Example: coupledmicrostrip = coupledMicrostripLine(GroundPlaneWidth=0.0400)

Data Types: double

Substrate — Type of dielectric material

dielectric object

Type of the dielectric material used as a substrate, specified as a dielectric object. The dielectric material in a coupledMicrostripLine object with default properties is Teflon. The thickness of the default dielectric material Teflon is 0.0016 m or the same as the Height property.

Example: d = dielectric("FR4"); coupledmicrostrip = coupledMicrostripLine(Substrate=d)

Data Types: string | char

Conductor — Type of metal used in conducting layers

metal object

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

Example: m = metal("PEC"); coupledmicrostrip =coupledMicrostripLine(Conductor=m)

Data Types: string | char

IsShielded — Flag to add metal shielding

false or 0 (default) | true or 1

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

Shielding — Metal shielding

shape.Box object

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.

Connector — Type of RF connector

RFConnector object

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

charge	Calculate and plot charge distribution
current	Calculate and plot current distribution
design	Design coupled microstrip transmission line around particular frequency
feedCurrent	Calculate current at feed port
getZ0	Calculate characteristic impedance of transmission line
getZEven	Calculate even mode impedance of differential PCB transmission line
getZOdd	Calculate odd mode impedance of differential PCB transmission line
rlgc	Compute resistances, inductances, conductances, and capacitances
propagationDelay	Compute propagation delay of transmission line
layout	Plot all metal layers and board shape
mesh	Change and view mesh properties of metal or dielectric in PCB component
shapes	Extract all metal layer shapes of PCB component
show	Display PCB component structure or PCB shape
layout	Plot all metal layers and board shape
sparameters	Calculate S-parameters for RF PCB objects
RFConnector	Create RF connector

Examples

Default Coupled Microstrip Line

Create a default coupled microstrip line.

cml = coupledMicrostripLine

cml = 
  coupledMicrostripLine with properties:

              Length: 0.0271
               Width: 0.0051
             Spacing: 0.0046
              Height: 0.0016
    GroundPlaneWidth: 0.0300
           Substrate: [1x1 dielectric]
           Conductor: [1x1 metal]
          IsShielded: 0

View the coupled microstrip line.

show(cml)

Multilayer Coupled Microstrip Line

Design and view a coupled microstrip line at the interface of a multilayer dielectric.

cml = design(coupledMicrostripLine,4e9,Z0e=75,Z0o=36);
cml.Substrate = dielectric(Name=["Teflon","Teflon"],EpsilonR=[2.1 2.1], ...
    LossTangent=[0 0],Thickness=[0.8e-3 0.8e-3]);
cml.Height = 0.8e-3;
show(cml)

Plot the current and charge distribution on the transmission line.

current(cml,4e9)

figure
charge(cml,4e9)

More About

Parametric Analysis

Use the design function to change the even impedance (Zoe) and the odd impedance (Zoo) of the coupled microstrip line.

• Increasing the difference between the even impedance (Zoe) and the odd impedance (Zoo) decreases the distance between the lines.

• Increasing the difference between Zoe and Zoo increases the power at the coupled ports.

• The impedance of the coupled lines Zo is the geometric mean of Zoe and Zoo. If the even and odd impedance values do not satisfy this condition, then calculate the S-parameters using Zo to get a proper match.

References

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

[2] “Microwaves101 | Coupled Line Couplers.” Accessed July 7, 2021. https://www.microwaves101.com/encyclopedias/coupled-line-couplers.

Version History

Introduced in R2021b

R2023b: Metal shielding for coupled microstrip line

Use the IsShielded, Shielding, and Connector properties to add a metal shield to the coupledMicrostripline object.