couplerRatrace

Create equal-split rat-race coupler or 180-degree-ring hybrid

Since R2021b

Description

Use the couplerRatrace object to create an equal-split rat-race coupler or a 180-degree-ring hybrid.

The rat-race coupler is used as a splitter with a phase shift. When given two inputs, the coupler can create sum and difference ports for added and subtracted power. It also acts as an interface between transmitters and receivers for integrating with an antenna and in building circuits with complex functionality like a comparator with sum and difference ports.

There are four ports and the circumference is 1.5 λ. The phase shift between the output ports is 180 degrees. When you apply an input at port 1, port 2 and port 4 are coupled ports, where the output has a phase difference of 180 degrees, and port 3 is the isolated port. When you apply an input at port 3, the output is split equally with same phase at port 2 and port 4.

To analyze the behavioral model for the rat-race coupler, set the Behavioral property in the sparameters to true or 1.

Creation

Syntax

coupler = couplerRatrace

coupler = couplerRatrace(Name=Value)

Description

coupler = couplerRatrace creates a rat-race coupler with default property values for a frequency of 3 GHz.

coupler = couplerRatrace(Name=Value) sets Properties using one or more name-value arguments. For example, couplerRatrace(PortLineLength=0.0286) creates a rat-race coupler with a port line length of 0.0286 meters. Properties not specified retain their default values.

Properties

PortLineLength — Length of input and output line

0.0186 (default) | positive scalar

Length of the input and the output line in meters, specified as a positive scalar.

Example: coupler = couplerRatrace(PortLineLength=0.0286)

Data Types: double

PortLineWidth — Width of input and output line

0.0050 (default) | positive scalar

Width of the input and the output line in meters, specified as a positive scalar.

Example: coupler = couplerRatrace(PortLineWidth=0.0070)

Data Types: double

CouplerLineWidth — Width of coupler line

0.0030 (default) | positive scalar

Width of the coupler line in meters, specified as a positive scalar. The default value is for a λ/4 line with an impedance of Zo/sqrt(2) ohms.

Example: coupler = couplerRatrace(CouplerLineWidth=0.0070)

Data Types: double

Circumference — Length of coupler line

0.1110 (default) | positive scalar

Length of the coupler line in meters, specified as a positive scalar. The default value is for a 1.5 λ line with an impedance of Zo/sqrt(2) ohms.

Example: coupler = couplerRatrace(Circumference=0.2303)

Data Types: double

Height — Height of rat-race coupler from ground plane

0.0016 (default) | positive scalar

Height of the rat-race coupler from the ground plane in meters, specified as a positive scalar.

In the case of a multilayer substrate, you can use the Height property to create a rat-race coupler where the two dielectrics interface.

Example: coupler = couplerRatrace(Height=0.0015)

Data Types: double

Substrate — Type of dielectric material

dielectric object

Type of dielectric material used as a substrate, specified as a dielectric object. The dielectric material in a couplerRatrace 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"); coupler = couplerRatrace(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 couplerRatrace object with default properties is Copper.

Example: m = metal("PEC"); coupler = couplerRatrace(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
coupling	Calculate coupling factor of coupler
current	Calculate and plot current distribution
design	Design rat-race coupler around specified frequency
directivity	Calculate directivity of coupler
feedCurrent	Calculate current at feed port
getZ0	Calculate characteristic impedance of transmission line
isolation	Calculate isolation of coupler
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
sparameters	Calculate S-parameters for RF PCB objects
RFConnector	Create RF connector

Examples

Create Default Rat-Race Coupler

Create and view a default rat-race coupler.

ratrace = couplerRatrace

ratrace = 
  couplerRatrace with properties:

      PortLineLength: 0.0186
       PortLineWidth: 0.0050
    CouplerLineWidth: 0.0030
       Circumference: 0.1110
              Height: 0.0016
           Substrate: [1x1 dielectric]
           Conductor: [1x1 metal]
          IsShielded: 0

show(ratrace)

Calculate Current Distribution on Rat-Race Coupler

Create a rat-race coupler with default properties.

coupler = couplerRatrace;

Set the excitation voltage and the phase angle at the ports of the coupler.

v = voltagePort(4)

v = 
  voltagePort with properties:

         NumPorts: 4
      FeedVoltage: [1 0 0 0]
        FeedPhase: [0 0 0 0]
    PortImpedance: 50

v.FeedVoltage = [1 0 1 0]

v = 
  voltagePort with properties:

         NumPorts: 4
      FeedVoltage: [1 0 1 0]
        FeedPhase: [0 0 0 0]
    PortImpedance: 50

v.FeedPhase = [90 0 270 0]

v = 
  voltagePort with properties:

         NumPorts: 4
      FeedVoltage: [1 0 1 0]
        FeedPhase: [90 0 270 0]
    PortImpedance: 50

Calculate and plot the current on the coupler at 3 GHz.

figure
current(coupler,3e9,Excitation=v,Type='real',Direction='on')

References

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

Version History

Introduced in R2021b

R2023b: Metal shielding for Rat Race coupler

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

R2022b: Behavioral Analysis for Rat-Race Coupler

Use the sparameters function and the pcbElement object to perform the behavioral analysis of a rat-race coupler.