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:

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

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.

Creation

Syntax

dh = dipoleHelix

dh = dipoleHelix(Name=Value)

Description

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

• 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

Radius — Turn radius

0.0220 (default) | scalar | tunable for dipoleHelix type AIAntenna

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

Width — Strip width

1.0000e-03 (default) | scalar | tunable for dipoleHelix type AIAntenna

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

Turns — Number of turns of helical dipole

3 (default) | scalar

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

Example: Turns=2

Data Types: double

Spacing — Spacing between turns

0.0350 (default) | scalar | tunable for dipoleHelix type AIAntenna

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

WindingDirection — Direction of helical dipole turns (windings)

"CCW" (default) | "CW"

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

Example: WindingDirection="CW"

Data Types: string

Substrate — Type of dielectric material

"Air" (default) | dielectric object

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')

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: Conductor=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: Load=lumpedElement(Impedance=75)

FeedOffset — Signed distance of feedpoint 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 feedpoint relative to the ground plane and patch.

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/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

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 Model Based Helical Dipole Antenna

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

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™.