cavity

Create cavity-backed antenna

Description

The cavity object is a cavity-backed antenna located on the xyz- plane. The default cavity antenna has a dipole as an exciter. The feed point is on the exciter.

Creation

Syntax

c = cavity

c = cavity(Name=Value)

Description

c = cavity creates a cavity backed antenna located on the X-Y-Z plane. By default, the dimensions are chosen for an operating frequency of 1 GHz.

c = cavity(Name=Value) creates a cavity-backed antenna, with additional Properties specified by 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 not specified retain their default values.

Properties

Exciter — Antenna or array to use as exciter

dipole (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 Toolbox™ antenna or array element as an exciter. To create the cavity backing structure without the exciter, specify this property as an empty array.

Example: horn

Example: linearArray(Element=patchMicrostrip)

Example: []

Substrate — Type of dielectric material

'Air' (default) | dielectric object

Type of dielectric material used as a substrate, specified as a dielectric object. For more information see, dielectric. For more information on dielectric substrate meshing, see Meshing.

Note

The substrate dimensions must be equal to the ground plane dimensions.

Example: dielectric("FR4")

Length — Length of rectangular cavity along x-axis

0.2000 (default) | scalar

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

Example: 30e-2

Data Types: double

Width — Width of rectangular cavity along y-axis

0.2000 (default) | scalar

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

Example: 25e-2

Data Types: double

Height — Height of rectangular cavity along z-axis

0.0750 (default) | scalar

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

Example: 7.5e-2

Data Types: double

Spacing — Distance between exciter and base of cavity

0.0750 (default) | scalar

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

Example: 7.5e-2

Data Types: double

Conductor — Type of metal material

"PEC" (default) | metal object

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

Example: metal("Copper")

Load — Lumped elements

[1x1 lumpedElement] (default) | lumped element object

Lumped elements added to the antenna feed, specified as a lumped element object. For more information, see lumpedElement.

Example: lumpedElement(Impedance=75)

EnableProbeFeed — Create probe feed from backing structure to exciter

0 (default) | 1

Create probe feed from backing structure to exciter, specified as a 0 or 1. By default, probe feed is not enabled.

Example: 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/or plot axial ratio of antenna or array
bandwidth	Calculate and/or plot absolute bandwidth of antenna
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	Radiation efficiency of antenna
EHfields	Electric and magnetic fields of antennas or embedded electric and magnetic fields of antenna element in arrays
impedance	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
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
rcs	Calculate and plot monostatic and bistatic radar cross section (RCS) of platform, antenna, or array
resonantFrequency	Calculate and/or plot resonant frequency of antenna
returnLoss	Return loss of antenna or scan return loss of array
show	Display antenna, array structures, shapes, or platform
sparameters	Calculate S-parameters for antennas and antenna arrays
vswr	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