# dipoleHelix

Create regular or AI-based helical dipole antenna

## Description

The dipoleHelix object is a helical dipole antenna. The antenna is typically center-fed. 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.

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.

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:

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

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.

## Creation

### Description

example

dh = dipoleHelix creates a helical dipole antenna. The default antenna operates at around 2 GHz.

example

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.

• You can also create a dipoleHelix antenna resonating at a desired frequency using the design function.

• You can also create a dipoleHelix antenna from a dipole helix type AIAntenna object using the exportAntenna function.

• A dipoleHelix type AIAntenna has some common tunable properties with a regular dipoleHelix antenna for AI-based analysis. Other properties of the regular dipoleHelix antenna are retained as read-only in its AIAntenna equivalent. To find the upper and lower bounds of the tunable properties, use tunableRanges function.

## Properties

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Turn radius, specified as a scalar in meters. This property is tunable for dipoleHelix type AIAntenna object created using the design function.

Data Types: double

Strip width, specified as a scalar in meters. This property is tunable for dipoleHelix type AIAntenna object created using the design function.

Note

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

Example: Width=5

Data Types: double

Number of turns of the helical dipole, specified a scalar.

Example: Turns=2

Data Types: double

Spacing between turns, specified as a scalar in meters. This property is tunable for dipoleHelix type AIAntenna object created using the design function.

Example: Spacing=1.5

Data Types: double

Direction of helical dipole turns (windings), specified as "CW" or "CCW".

Example: WindingDirection="CW"

Data Types: string

Type of dielectric material used as the substrate, specified as a dielectric object. 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: Substrate=dielectric('Teflon')

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: Conductor=metal('Copper');

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

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 feedpoint relative to the ground plane and patch.

Example: FeedOffset=[0.01 0.01]

Data Types: double

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

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.

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 wireStack Create single or multi-feed wire antenna

## Examples

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Create a default helical dipole antenna and view it.

dh = dipoleHelix
dh =
dipoleHelix with properties:

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]

show(dh)

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

show(dh)

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

pattern(dh, 1.8e9);

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

d = dielectric('Teflon');
dh =
dipoleHelix with properties:

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]

View the dipole helix antenna.

show(dh)

This example shows how to create an AI model based helical dipole antenna at 2GHz 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
Spacing: 0.0239
Width: 0.0016

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

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:

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

## 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

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