cavity

Create square or rectangular cavity-backed antenna

Description

The default cavity object creates a square cavity-backed antenna resonating around 850 MHz. By default, a dipole element is used as an exciter for this antenna. The feed point is located on the exciter.

Creation

Syntax

c = cavity

c = cavity(Name=Value)

Description

c = cavity creates a square cavity-backed antenna with default property values. The default dimensions are chosen for an operating frequency of around 850 MHz.

c = cavity(Name=Value) sets properties using one or more name–value arguments. Name is the property name and Value is the corresponding value. You can specify several name-value arguments in any order as Name1=Value1,...,NameN=ValueN. Properties that you do not specify, retain their default values.

For example, c = cavity(Height=0.1) creates a square-cavity backed antenna with cavity height of 0.1 m. and default values for other properties.

Properties

Length — Length of rectangular cavity along x-axis

0.2 (default) | positive scalar

Length of the rectangular cavity along x-axis, specified as a positive scalar in meters.

Example: 30e-2

Data Types: double

Width — Width of rectangular cavity along y-axis

0.2 (default) | positive scalar

Width of the rectangular cavity along y-axis, specified as a positive scalar in meters.

Example: 25e-2

Data Types: double

Height — Height of rectangular cavity along z-axis

0.075 (default) | positive scalar

Height of the rectangular cavity along z-axis, specified as a positive scalar in meters.

Example: 10e-2

Data Types: double

Exciter — Exciter antenna or array type

dipole object (default) | antenna object | array object | empty array

Exciter antenna or array type, specified as a single-element antenna object, an array object, or an empty array. Except for reflector and cavity antenna elements, you can use any antenna object from the antenna catalog or an array object from the array catalog as an exciter. To create the cavity backing structure without an exciter, specify this property as an empty array.

Example: Exciter=horn

Example: Exciter=linearArray(Element=patchMicrostrip)

Example: Exciter=[];

Spacing — Distance between exciter and base of cavity

0.075 (default) | positive scalar

Distance between the exciter and the base of the cavity, specified as a positive scalar in meters.

Example: 10e-2

Data Types: double

Substrate — Type of dielectric material

dielectric("Air") (default) | dielectric object

Type of dielectric material used as a substrate, specified as a dielectric object. You can choose any dielectric material from the DielectricCatalog or specify a dielectric material of your choice. The substrate dimensions must be equal to the ground plane dimensions. For more information on dielectric substrate meshing, see Meshing.

Example: dielectric("FR4")

Conductor — Type of metal

metal("PEC") (default) | metal object

Type of the metal used as a conductor, specified as a metal object. You can choose any metal from the MetalCatalog or specify a metal of your choice. For more information on metal conductor meshing, see Meshing.

Example: metal("Copper")

Load — Lumped elements

[1x1 lumpedElement] (default) | lumpedElement object

Lumped elements added to the antenna feed, specified as a lumpedElement object. You can add a load anywhere on the surface of the antenna. By default, the load is at the feed.

Example: Load=lumpedElement(Impedance=75)

Example: antenna.Load = lumpedElement(Impedance=75)

EnableProbeFeed — Option to create probe feed from backing structure to exciter

0 (default) | 1

Option to create probe feed from backing structure to exciter, specified as a numeric 0 or 1. Specify 0 to disable or 1 to enable the probe feed. By default, probe feed is disabled.

Example: EnableProbeFeed=1

Data Types: double

Tilt — Tilt angle of antenna

0 (default) | scalar | vector

Tilt angle of the antenna in degrees, specified as a scalar or vector. For more information, see Rotate Antennas and Arrays.

Example: 90

Example: Tilt=[90 90],TiltAxis=[0 1 0;0 1 1] tilts the antenna at 90 degrees about the two axes defined by the vectors.

Data Types: double

TiltAxis — Tilt axis of antenna

[1 0 0] (default) | three-element vector | 2-by-3 matrix | "X" | "Y" | "Z"

Tilt axis of the antenna, specified as one of these values:

• Three-element vector of Cartesian coordinates in meters. In this case, each coordinate in the vector starts at the origin and lies along the specified points on the x-, y-, and z-axes.

• Two points in space, specified as a 2-by-3 matrix corresponding to two three-element vectors of Cartesian coordinates. In this case, the antenna rotates around the line joining the two points.

• "x", "y", or "z" to describe a rotation about the x-, y-, or z-axis, respectively.

For more information, see Rotate Antennas and Arrays.

Example: [0 1 0]

Example: [0 0 0;0 1 0]

Example: "Z"

Data Types: double | string

Object Functions

axialRatio	Calculate and plot axial ratio of antenna or array
bandwidth	Calculate and plot absolute bandwidth of antenna or array
beamwidth	Beamwidth of antenna
charge	Charge distribution on antenna or array surface
current	Current distribution on antenna or array surface
design	Design prototype antenna or arrays for resonance around specified frequency or create AI-based antenna from antenna catalog objects
efficiency	Calculate and plot radiation efficiency of antenna or array
EHfields	Electric and magnetic fields of antennas or embedded electric and magnetic fields of antenna element in arrays
feedCurrent	Calculate current at feed for antenna or array
impedance	Calculate and plot input impedance of antenna or scan impedance of array
info	Display information about antenna, array, or platform
memoryEstimate	Estimate memory required to solve antenna or array mesh
mesh	Mesh properties of metal, dielectric antenna, or array structure
meshconfig	Change meshing mode of antenna, array, custom antenna, custom array, or custom geometry
msiwrite	Write antenna or array analysis data to MSI planet file
optimize	Optimize antenna or array using SADEA optimizer
pattern	Plot radiation pattern and phase of antenna or array or embedded pattern of antenna element in array
patternAzimuth	Azimuth plane radiation pattern of antenna or array
patternElevation	Elevation plane radiation pattern of antenna or array
peakRadiation	Calculate and mark maximum radiation points of antenna or array on radiation pattern
rcs	Calculate and plot monostatic and bistatic radar cross section (RCS) of platform, antenna, or array
resonantFrequency	Calculate and plot resonant frequency of antenna
returnLoss	Calculate and plot return loss of antenna or scan return loss of array
show	Display antenna, array structures, shapes, or platform
sparameters	Calculate S-parameters for antenna or array
stlwrite	Write mesh information to STL file
vswr	Calculate and plot voltage standing wave ratio (VSWR) of antenna or array element

Examples

Create and View Cavity-Backed Antenna

Create and view a cavity-backed dipole antenna with 30 cm length, 25 cm width, 7.5 cm height and spaced 7.5 cm from the bowtie for operation at 1 GHz.

c = cavity(Length=30e-2,Width=25e-2,Height=7.5e-2,Spacing=7.5e-2);
show(c)

Radiation Pattern of Cavity-Backed Antenna

Create a cavity-backed antenna using a dielectric substrate 'FR4'.

d = dielectric('FR4');
c = cavity(Length=30e-2,Width=25e-2,Height=20.5e-3,Spacing=7.5e-3,...
    Substrate=d)

c = 
  cavity with properties:

            Exciter: [1x1 dipole]
          Substrate: [1x1 dielectric]
             Length: 0.3000
              Width: 0.2500
             Height: 0.0205
            Spacing: 0.0075
    EnableProbeFeed: 0
          Conductor: [1x1 metal]
               Tilt: 0
           TiltAxis: [1 0 0]
               Load: [1x1 lumpedElement]

show(c)

Plot the radiation pattern of the antenna at a frequency of 1 GHz.

figure
pattern(c,1e9)

Create Rectangular Array with Cavity Backing Structure

Create a rectangular array of E-shaped patch antenna.

rectArr = rectangularArray(Element=patchMicrostripEnotch,RowSpacing=0.03,ColumnSpacing=0.03);

Create a cavity-backed antenna with rectangular array exciter.

ant = cavity(Exciter=rectArr)

ant = 
  cavity with properties:

            Exciter: [1x1 rectangularArray]
          Substrate: [1x1 dielectric]
             Length: 0.2000
              Width: 0.2000
             Height: 0.0750
            Spacing: 0.0750
    EnableProbeFeed: 0
          Conductor: [1x1 metal]
               Tilt: 0
           TiltAxis: [1 0 0]
               Load: [1x1 lumpedElement]

show(ant)

Create Fractal Carpet Antenna with Cavity Backing structure

Create and visualize a cavity-backed fractal carpet antenna

e = fractalCarpet(Substrate=dielectric('FR4'));
ant = cavity(Exciter=e)

ant = 
  cavity with properties:

            Exciter: [1x1 fractalCarpet]
          Substrate: [1x1 dielectric]
             Length: 0.2000
              Width: 0.2000
             Height: 0.0750
            Spacing: 0.0750
    EnableProbeFeed: 0
          Conductor: [1x1 metal]
               Tilt: 0
           TiltAxis: [1 0 0]
               Load: [1x1 lumpedElement]

show(ant)

Analyze Cavity Structure Using Plane Wave Excitation

This example shows how to create and analyze a cavity-shaped backing structure without an exciter element using planeWaveExcitation.

Create Cavity Antenna

Create a cavity antenna operating at 1 GHz using the design function and the cavity element from the antenna catalog. Display the antenna.

f = 1e9;
ant = design(cavity,f);
figure
show(ant)

Derive Backing Structure

Derive the backing structure from the cavity antenna by specifying the 'Exciter' property as an empty array.

ant.Exciter = []

ant = 
  cavity with properties:

            Exciter: []
          Substrate: [1x1 dielectric]
             Length: 0.1690
              Width: 0.1690
             Height: 0.0634
            Spacing: 0.0634
    EnableProbeFeed: 0
          Conductor: [1x1 metal]
               Tilt: 0
           TiltAxis: [1 0 0]
               Load: [1x1 lumpedElement]

Display the backing structure.

figure
show(ant)

Mesh Backing Structure

Mesh the cavity structure with a maximum edge length of 10 mm.

figure
mesh(ant,MaxEdgeLength=10e-3)

Plot Directivity Pattern

Use the cavity backing structure as a receiver element in a plane wave excitation environment and plot its directivity at 1 GHz.

pw = planeWaveExcitation(Element=ant);
figure
pattern(pw,f)

References

[1] Balanis, Constantine A. Antenna Theory: Analysis and Design. Fourth edition. Hoboken, New Jersey: Wiley, 2016.

Version History

Introduced in R2015a