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dipoleHelix

Create 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.

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. The circular ground plane is on the X-Y plane. 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:

x=rcos(θ)y=rsin(θ)z=Sθ

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 around 2 GHz.

example

dh = dipoleHelix(Name,Value) creates a helical dipole antenna, with additional properties specified by one or more name–value pair arguments. Name is the property name and Value is the corresponding value. You can specify several name-value pair arguments in any order as Name1, Value1, ..., NameN, ValueN. Properties not specified retain their default values.

Properties

expand all

Turn radius, specified as a scalar in meters.

Example: 'Radius',2

Data Types: double

Strip width, specified as a scalar in meters.

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.

Example: 'Spacing',1.5

Data Types: double

Direction of helical dipole turns (wingdings), specified as 'CW' or 'CCW'.

Example: 'WindingDirection','CW'

Data Types: string

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

Example: 'Load',lumpedelement. lumpedelement is the object handle for the load created using 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 antenna, specified as a scalar or vector with each element unit in degrees.

Example: 'Tilt',90

Example: 'Tilt',[90 90 0]

Data Types: double

Tilt axis of the antenna, specified as:

  • A three-element vector of Cartesian coordinates in meters. In this case, each vector starts at the origin and lies along the specified points on the X, Y, and Z axes.

  • Two points in space as three-element vectors of Cartesian coordinates. In this case, the antenna rotates along the line joining the two points.

  • A string input for simple rotations around the principal planes, X, Y, or Z.

For more information see, Rotate Antenna and Arrays

Example: 'TiltAxis',[0 1 0]

Example: 'TiltAxis',[0 0 0;0 1 0]

Example: 'TiltAxis','Z'

Data Types: double

Object Functions

showDisplay antenna or array structure; Display shape as filled patch
infoDisplay information about antenna or array
axialRatioAxial ratio of antenna
beamwidthBeamwidth of antenna
chargeCharge distribution on metal or dielectric antenna or array surface
currentCurrent distribution on metal or dielectric antenna or array surface
designDesign prototype antenna for resonance at specified frequency
EHfieldsElectric and magnetic fields of antennas; Embedded electric and magnetic fields of antenna element in arrays
impedanceInput impedance of antenna; scan impedance of array
meshMesh properties of metal or dielectric antenna or array structure
meshconfigChange mesh mode of antenna structure
patternRadiation pattern of antenna or array; Embedded pattern of antenna element in array
patternAzimuthAzimuth pattern of antenna or array
patternElevationElevation pattern of antenna or array
returnLossReturn loss of antenna; scan return loss of array
sparametersS-parameter object
vswrVoltage standing wave ratio of antenna

Examples

expand all

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
                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);

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.

Introduced in R2016b

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