dipoleHelix

Create regular or AI-based helical dipole antenna

Description

The default dipoleHelix object is a center-fed helical dipole antenna resonating around 3.16 GHz. You can move the feed along the antenna length using the feed offset property. Helical dipoles are used in satellite communications and wireless power transfers.

The width of the strip is related to the diameter of an equivalent cylinder by this equation

$$w=2d=4r$$

where:

• w is the width of the strip.

• d is the diameter of an equivalent cylinder.

• r is the radius of an equivalent cylinder.

For a given cylinder radius, use the cylinder2strip utility function to calculate the equivalent width. The default helical dipole antenna is center-fed. Commonly, helical dipole antennas are used in axial mode. In this mode, the helical dipole circumference is comparable to the operating wavelength, and has maximum directivity along its axis. In normal mode, the helical dipole radius is small compared to the operating wavelength. In this mode, the helical dipole radiates broadside, that is, in the plane perpendicular to its axis. The basic equation for the helical dipole antenna is:

$$\begin{array}{l}x=r\cos (\theta )\\ y=r\sin (\theta )\\ z=S\theta \end{array}$$

where:

• r is the radius of the helical dipole.

• θ is the winding angle.

• S is the spacing between turns.

For a given pitch angle in degrees, use the helixpitch2spacing utility function to calculate the spacing between the turns in meters.

You can perform full-wave EM solver based analysis on the regular dipoleHelix antenna or you can create a dipoleHelix type AIAntenna and explore the design space to tune the antenna for your application using AI-based analysis.

Creation

Syntax

dh = dipoleHelix

dh = dipoleHelix(Name=Value)

Description

dh = dipoleHelix creates a regular center-fed helical dipole antenna with default property values. The default dimensions are chosen for an operating frequency of around 3.16 GHz.

dh = dipoleHelix(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, dh = dipoleHelix(Radius=0.02) creates a helical dipole antenna with a turns radius of 0.02 m and default values for other properties.

• You can also create a regular dipoleHelix antenna resonating at a desired frequency using the design function. For example, to create a regular dipoleHelix antenna resonating at 2 GHz, use the following syntax:

  >> design(dipoleHelix,2e9)
  

  To analyze this antenna use object functions of the dipoleHelix. Use this workflow to design, tune, and analyze a dipoleHelix antenna using conventional full-wave solvers.

• You can create an AI-based dipoleHelix antenna resonating at a desired frequency using the design function. Using AI-based antenna models over conventional full-wave solvers significantly reduces the simulation time required to fine-tune the antenna to meet your design goals. Set the ForAI argument in the design function to true to create a dipoleHelix type AIAntenna object. To use this feature, you need license to the Statistics and Machine Learning Toolbox™ in addition to the Antenna Toolbox™. For example, to create an AI-based dipoleHelix antenna resonating at 2 GHz, use the following syntax:

  >> design(dipoleHelix,2e9,ForAI=true)
  

  The AI-based dipoleHelix antenna retains the Radius, Width, and Spacing properties of the regular dipoleHelix antenna as tunable properties. Rest of the properties of the regular dipoleHelix antenna are converted into read-only properties in its AI-based version. To find the upper and lower bounds of the tunable properties, use the tunableRanges function.

  To analyze this antenna use object functions of the AIAntenna. Use this workflow to design, tune, and analyze a dipoleHelix antenna using its AI-based model. To create a regular dipoleHelix antenna from this AI-based antenna, use the exportAntenna function.

Properties

Radius — Turn radius

0.0220 (default) | positive scalar

Turn radius, specified as a positive scalar in meters. You can set this property for both regular and AI-based dipoleHelix antenna. For a regular dipoleHelix antenna, Radius value does not have any upper and lower bounds.

For AI-based dipoleHelix antenna, Radius value has upper and lower bounds. Use the tunableRanges function to get the upper and lower bound values.

Example: 2

Data Types: double

Width — Strip width

1.0000e-03 (default) | positive scalar

Strip width, specified as a positive scalar in meters. You can set this property for both regular and AI-based dipoleHelix antenna. For a regular dipoleHelix antenna, Width value does not have any upper and lower bounds.

For AI-based dipoleHelix antenna, Width value has upper and lower bounds. Use the tunableRanges function to get the upper and lower bound values.

Note

Strip width should be less than Radius/5 and greater than Radius/250. [4]

Example: 5

Data Types: double

Turns — Number of turns of helical dipole

3 (default) | positive scalar

Number of turns of the helical dipole, specified a positive scalar. You can set this property only for a regular dipoleHelix antenna. This property is read-only for the AI-based dipoleHelix antenna.

Example: 2

Data Types: double

Spacing — Spacing between turns

0.0350 (default) | positive scalar

Spacing between turns, specified as a positive scalar in meters. You can set this property for both regular and AI-based dipoleHelix antenna. For a regular dipoleHelix antenna, Spacing value does not have any upper and lower bounds.

For AI-based dipoleHelix antenna, Spacing value has upper and lower bounds. Use the tunableRanges function to get the upper and lower bound values.

Example: 1.5

Data Types: double

WindingDirection — Direction of helical dipole turns (windings)

"CCW" (default) | "CW"

Direction of helical dipole turns (windings), specified as "CW" or "CCW". You can set this property only for a regular dipoleHelix antenna. This property is read-only for the AI-based dipoleHelix antenna.

Example: "CW"

Data Types: string

Substrate — Type of dielectric material

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

Type of dielectric material used as the substrate, specified as a dielectric object. You can choose any dielectric material from the DielectricCatalog or specify a dielectric material of your choice. You can set this property only for a regular dipoleHelix antenna.

You can specify only one dielectric layer in the dipoleHelix object. Specify the same radius for all the turns. When you use a dielectric material other than air, the number of turns in the dipole helix must be greater than 1. For more information on dielectric substrate meshing, see Meshing.

Example: dielectric("Teflon")

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. You can set this property only for a regular dipoleHelix antenna. For more information on metal conductor meshing, see Meshing.

Example: metal("Copper");

Load — Lumped elements

[1x1lumpedElement] (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. You can set this property only for a regular dipoleHelix antenna.

Example: Load=lumpedElement(Impedance=75)

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

FeedOffset — Signed distance of feed point from origin

0 (default) | two-element vector

Signed distance from center along length and width of ground plane, specified as a two-element vector in meters. Use this property to adjust the location of the feed point relative to the ground plane and patch. You can set this property only for a regular dipoleHelix antenna. This property is read-only for the AI-based dipoleHelix antenna.

Example: FeedOffset=[0.01 0.01]

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
wireStack	Create single or multi-feed wire antenna

Examples

Helical Dipole Antenna

Create a default helical dipole antenna and view it.

dh = dipoleHelix

dh = 
  dipoleHelix with properties:

              Radius: 0.0220
               Width: 1.0000e-03
               Turns: 3
             Spacing: 0.0350
    WindingDirection: 'CCW'
          FeedOffset: 0
           Substrate: [1x1 dielectric]
           Conductor: [1x1 metal]
                Tilt: 0
            TiltAxis: [1 0 0]
                Load: [1x1 lumpedElement]

show(dh)

Radiation Pattern of Helical Dipole

Create a four-turn helical dipole antenna with a turn radius of 28 mm and a strip width of 1.2 mm.

dh = dipoleHelix(Radius=28e-3, Width=1.2e-3, Turns=4);
show(dh)

Plot the radiation pattern of the helical dipole at 1.8 GHz.

pattern(dh, 1.8e9);

Dipole Helix Antenna with Dielectric Substrate

Create a custom dipole helix antenna with a Teflon dielectric substrate.

d = dielectric('Teflon');
dh = dipoleHelix(Radius=22e-3,Width=1e-3,Turns=3,Spacing=35e-3,FeedOffset=0,Substrate=d)

dh = 
  dipoleHelix with properties:

              Radius: 0.0220
               Width: 1.0000e-03
               Turns: 3
             Spacing: 0.0350
    WindingDirection: 'CCW'
          FeedOffset: 0
           Substrate: [1x1 dielectric]
           Conductor: [1x1 metal]
                Tilt: 0
            TiltAxis: [1 0 0]
                Load: [1x1 lumpedElement]

View the dipole helix antenna.

show(dh)

Create AI-Based Helical Dipole Antenna

This example shows how to create an AI-based helical dipole antenna at 2 GHz and calculate its resonant frequency.

pAI = design(dipoleHelix,2e9,ForAI=true)

pAI = 
  AIAntenna with properties:

   Antenna Info
               AntennaType: 'dipoleHelix'
    InitialDesignFrequency: 2.0000e+09

   Tunable Parameters
                    Radius: 0.0171
                   Spacing: 0.0239
                     Width: 0.0016

Use 'showReadOnlyProperties(pAI)' to show read-only properties

showReadOnlyProperties(pAI)

                    Turns: 15
         WindingDirection: 'CW'
               FeedOffset: 0

            SubstrateName: 'Air'
        SubstrateEpsilonR: 1
     SubstrateLossTangent: 0
       SubstrateThickness: 0.3602

            ConductorName: 'PEC'
    ConductorConductivity: Inf
       ConductorThickness: 0

                     Tilt: 0
                 TiltAxis: [1 0 0]

            LoadImpedance: []
            LoadFrequency: []
             LoadLocation: 'feed'

Vary the helix radius, turns spacing, and width. Calculate its resonant frequency.

pAI.Radius = 0.0146;
pAI.Spacing = 0.021;
pAI.Width = 0.0014;
fR = resonantFrequency(pAI)

fR = 
1.9960e+09

Convert the AIAntenna to a regular helical dipole antenna.

dh = exportAntenna(pAI)

dh = 
  dipoleHelix with properties:

              Radius: 0.0146
               Width: 0.0014
               Turns: 15
             Spacing: 0.0210
    WindingDirection: 'CW'
          FeedOffset: 0
           Substrate: [1x1 dielectric]
           Conductor: [1x1 metal]
                Tilt: 0
            TiltAxis: [1 0 0]
                Load: [1x1 lumpedElement]

References

[1] Balanis, C. A. Antenna Theory. Analysis and Design. 3rd Ed. Hoboken, NJ: John Wiley & Sons, 2005.

[2] Volakis, John. Antenna Engineering Handbook. 4th Ed. New York: McGraw-Hill, 2007.

Version History

Introduced in R2016b

R2024a: AI model based antenna analysis

Design, tune, and analyze this antenna using an AI model. Using AI-based antenna models over conventional full-wave solvers significantly reduces the simulation time required to fine-tune the antenna to meet your design goals. Set the ForAI argument in the design function to true to create a dipoleHelix type AIAntenna. To use this feature, you need license to the Statistics and Machine Learning Toolbox in addition to the Antenna Toolbox.