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stripLine

Create a transmission line in stripline form

Since R2024a

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Description

Use the stripLine object to create a transmission line in stripline form. Striplines are high speed transmission lines used for routing various RF components in the inner layers of a multi-layer printed circuit board (PCB). The structure consists of a transmission line trace surrounded by dielectric material suspended between two ground planes.

For the electromagnetic (EM) interactions between the ground planes, the feeds are located on the centers of the strip's edges at the board boundary and are simultaneously excited against both ground planes.

Types and applications of stripline routing techniques:

To create the asymmetric and suspended stripline types every field of Substrate must be expanded into a 1xN vector/cell array, where N is the total number of desired nonmetal layers.

The substrate layers are constructed from bottom to top. The information from Entry 1 of each of these vectors is taken to describe the bottom substrate layer, Entry 2 specifies the second-from-bottom, and so forth.

The stripline’s Height specifies the height of the strip above the bottom ground plane. One of the substrate layers must terminate at exactly Height to avoid an execution error.

The height of the stripline’s top ground plane is automatically set to the total of the thicknesses of all dielectric layers. Note that Height does not govern the height of the top ground plane above the strip.

Note

The value of Height is the height of the strip above the bottom ground plane. For the symmetric stripline the default total PCB thickness - height of the top ground plane above the bottom ground plane - is 2*Height.

Creation

Syntax

strip = stripLine
strip = stripLine(name = value)

Description

example

strip = stripLine creates a default strip transmission line. The default dimensions are for a frequency range of 1 GHz to 5 GHz. The default transmission line lies in the X-Y plane.

example

strip = stripLine(name = value) sets Properties using one or more name value arguments. For example, strip = stripLine('Length',0.0300) creates a strip transmission line of length 0.0300 meters. Properties not specified retain their default values.

Properties

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

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

Data Types: double

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

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

Data Types: double

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

Example: strip = stripLine('Height',0.0026)

Data Types: double

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

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

Data Types: double

Type of dielectric material used as a substrate, specified as a dielectric object. The values of the default dielectric material are: ('Name',{'Teflon'},'EpsilonR',2.1, 'LossTangent',0.0002,'Thickness',0.0060) For more information see dielectric.

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

Data Types: string | char

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

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

Data Types: string | char

Object Functions

chargeCalculate and plot charge distribution
currentCalculate and plot current distribution
designDesign PCB component 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
showDisplay PCB component structure or PCB shape
sparametersCalculate S-parameters for RF PCB objects

Examples

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Open Live Script

Create and view a transmission line in the form of a strip.

txstrip = stripLine
txstrip = 
  stripLine with properties:

              Length: 0.0202
               Width: 0.0027
              Height: 0.0016
    GroundPlaneWidth: 0.0150
           Substrate: [1×1 dielectric]
           Conductor: [1×1 metal]


show(txstrip)

Open Live Script

Create, show and analyze a symmetric stripline transmission line

freq = linspace(1e9, 5e9, 41);
s1 = stripLine;
figure; show(s1);
title('Symmetric stripline');

sp1 = sparameters(s1, freq);
figure; rfplot(sp1, 1:2, 1);
title('Symmetric stripline');

Open Live Script

Create, show and analyze an asymmetric stripline transmission line

freq = linspace(1e9, 5e9, 41);
s2 = stripLine;
s2.Substrate.Name        = {'Teflon', 'Teflon'};
s2.Substrate.EpsilonR    = [2.1        2.1];
s2.Substrate.LossTangent = [2e-4       2e-4];
s2.Substrate.Thickness   = [s2.Height  s2.Height/2];
figure; show(s2);
title('Asymmetric stripline');

sp2 = sparameters(s2, freq);
figure; rfplot(sp2, 1:2, 1)
title('Asymmetric stripline');

Open Live Script

Create, show and analyze a suspended stripline transmission line

freq = linspace(1e9, 5e9, 41);
s3 = stripLine;
suspendedSubThickness = 0.001;
t1 = s3.Height - suspendedSubThickness; % Thickness of air gap below suspended dielectric
t2 = suspendedSubThickness;             % Thickness of suspended dielectric
t3 = t1 + t2;                           % Thickness of air gap above suspended dielectric
s3.Substrate.Name        = {'Air', 'Teflon', 'Air'};
s3.Substrate.EpsilonR    = [1      2.1       1];
s3.Substrate.LossTangent = [0      2e-4      0];
s3.Substrate.Thickness   = [t1     t2        t3];
figure; show(s3)
title('Suspended stripline');

sp3 = sparameters(s3, freq);
figure; rfplot(sp3, 1:2, 1);
title('Suspended stripline')

More About

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Version History

Introduced in R2024a

See Also

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