# 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

### Syntax

``dh = dipoleHelix``
``dh = dipoleHelix(Name=Value)``

### 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.

Example: `Radius=2`

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`.

Example: `Load=lumpedElement(Impedance=75)`

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: 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)`

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);`

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)`

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 Radius: 0.0171 Spacing: 0.0239 Width: 0.0016 Use 'showReadOnlyProperties(pAI)' to show read-only properties ```

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

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