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coupledStripLine

Create coupled transmission line in stripline form

Description

Use the coupledStripLine object to create a coupled transmission line in a stripline form. Coupled striplines are used to connect different RF components like couplers and dividers within the PCB board.

Types and applications of stripline routing techniques:

  • Symmetric or Plain — Transmission lines routed on the internal layers.

  • Asymmetric — Transmission lines not centrally embedded in the ground plane. Asymmetric striplines are placed close to one of the ground planes. When routing signals the closer ground plane is used as a reference to ensure stronger return signal.

  • Edge-Coupled — Routing technique used for differential pairs. It has the same structure as the symmetric stripline routing but with trace spacing for the differential pair.

  • Suspended — Printed stripline with a strip conductor centered between two parallel ground planes and placed on a dielectric surface. The substrate is suspended in a metal closer. The major portion of the EM field is confined to the air gaps between dielectric substrates and ground planes.

Creation

Description

example

sline = coupledStripLine creates a default coupled transmission line in the strip line form. The default properties are for a resonant frequency of 2.5 GHz along the X-Y plane.

example

sline = coupledStripLine('propety1',value1,'property2',value2...) sets properties using one or more name value pair arguments. For example, sline = coupledStripLine('Length',0.0300) creates a coupled strip line of length 0.0300 meters. Properties not specified retains their default values.

Properties

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

Example: strip = coupledStripLine('Length',0.0300)

Data Types: double

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

Example: strip = coupledStripLine('Width',0.0037)

Data Types: double

Spacing between the coupled lines in meters, specified as a positive scalar.

Example: strip = coupledStripLine('Spacing',0.00037)

Data Types: double

Height from the ground plane to the coupled strip line in meters, specified as a positive scalar.

Example: strip = coupledStripLine('Height',9.000e-04)

Data Types: double

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

Example: strip = coupledStripLine('GroundPlaneWidth',0.0350)

Data Types: double

Type of dielectric material used as a substrate, specified as a dielectric object. For more information see dielectric. The default dielectric material Teflon has an EpsilonR of 2.2, la oss tangent of 0.03, and a thickness of 0.0032.

Example: d = dielectric('FR4'); strip = coupledStripLine('Substrate',d)

Data Types: string | char

Type of metal used for the conducting layers, specified as a metal object. For more information see metal.

Example: m = metal('PEC'); strip = coupledSripLine('Conductor',m)

Data Types: string | char

Object Functions

chargeCalculate and plot charge distribution
currentCalculate and plot current distribution
designDesign symmetric coupled strip transmission line around given frequency
feedCurrentCalculate current at feed port
getZ0Calculate characteristic impedance of transmission line
meshChange and view mesh properties of metal or dielectric in PCB component
showDisplay PCB component structure or PCB shape
sparametersCalculate S-parameters for RF PCB objects

Examples

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Create and view a coupled strip line at the interface of a multi-layered dielectric.

sub = dielectric('FR4','Teflon');
sub.Thickness = [0.003 0.001];
coupledstripline = coupledStripLine('Height',0.003,'Substrate',sub);
show(coupledstripline);

Plot the charge and current distribution on this transmission line.

current(coupledstripline,2.5e9)

figure;
charge(coupledstripline,2.5e9)

More About

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References

[1] Pozar, Microwave Engineering / David M. Pozar, University of Massachusetts at Amherst.

[2] Cohn, S.B. “Shielded Coupled-Strip Transmission Line.” IEEE Transactions on Microwave Theory and Techniques 3, no. 5 (October 1955): 29–38. https://doi.org/10.1109/TMTT.1955.1124973.

Introduced in R2021b