dipoleHelixMultifilar

Create balanced bifilar or quadrafilar dipole helix antenna without circular ground plane

Description

The dipoleHelixMultifilar object creates a balanced bifilar or quadrafilar helix antenna without a circular ground plane. You can create both short-circuited and open-ended dipole helix multifilar antennas. Bifilar and quadrafilar helix antennas are used in aerospace and defense applications.

The width of the strip is related to the diameter of an equivalent cylinder by the 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 helix antenna is end-fed. The circular ground plane is on the X-Y plane. Helix antennas are used commonly in axial mode. In this mode, the helix circumference is comparable to the operating wavelength, and the helix has maximum directivity along its axis. In normal mode, the helix radius is small compared to the operating wavelength. In this mode, the helix radiates broadside, that is, in the plane perpendicular to its axis. The basic equations for the helix are

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

ant = dipoleHelixMultifilar
ant = dipoleHelixMultifilar(Name,Value)

Description

example

ant = dipoleHelixMultifilar creates a bifilar or quadrafilar helix antenna without a circular ground plane. The default multifilar helical antenna is end-fed. The default helix operates around 2 GHz.

example

ant = dipoleHelixMultifilar(Name,Value) sets properties using one or more name-value pairs. For example, ant = dipoleHelixMultifilar('Radius',28e-03) creates a multifilar helix with turns of radius 28e-03 m. Enclose each property name in quotes.

Output Arguments

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Dipole multifilar helix antenna, returned as a dipoleHelixMultifilar object.

Properties

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Number of helical elements, specified as a 4 or 2. Two elements create a bifilar dipole helix antenna, and four elements create a quadrafilar dipole helix antenna.

Example: 'NumArms',2

Example: ant.NumArms = 2

Data Types: double

Radius of the turns, specified as a positive real scalar meter.

Example: 'Radius',28e-03

Example: ant.Radius = 28e-03

Data Types: double

Width of the strip, specified as a positive real scalar in meters.

Example: 'Width',0.2

Example: ant.Width = 0.2

Data Types: double

Number of turns, specified as a scalar integer.

Example: 'Turns',4

Example: ant.Turns = 4

Data Types: double

Spacing between the turns, specified as a positive real scalar in meters.

Example: 'Spacing',7.5e-2

Example: ant.Spacing = 7.5e-2

Data Types: double

Status of ends of the helix, specified as 0 or 1. By default, the dipoleHelixMultifilar is short circuited. Setting the property to 0 makes the helix antenna an open circuit.

Example: 'ShortEnds',0

Example: ant.ShortEnds = 0

Data Types: double

Direction of helix turns (windings), specified as CW or CCW.

Example: 'WindingDirection','CW'

Example: ant.WindingDirection = 'CW'

Data Types: char | string

Lumped elements added to the antenna feed, specified as a lumped element object handle. You can add a load anywhere on the surface of the antenna. By default, the load is at the origin. For more information, see lumpedElement.

Example: 'Load',lumpedelement. lumpedelement is the object handle for the load created using lumpedElement.

Example: ant.Load = lumpedElement('Impedance',75)

Data Types: double

Tilt angle of the antenna, specified as a scalar or vector with each element unit in degrees. For more information, see Rotate Antenna and Arrays.

Example: 'Tilt',90

Example: 'Tilt',[90 90]'TiltAxis',[0 1 0;0 1 1] tilts the antenna at 90 degree about two three-element vector points in space.

Data Types: double

Tilt axis of the antenna, specified as:

  • Three-element vectors 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, each specified as three-element vectors of Cartesian coordinates. In this case, the antenna rotates around the line joining the two points in space.

  • A string input describing simple rotations around one of the principal axes, '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: ant.TiltAxis = 'Z'

Object Functions

showDisplay antenna or array structure; Display shape as filled patch
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 or arrays 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 and phase 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

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Create and view a default multifilar helical dipole antenna.

ant = dipoleHelixMultifilar
ant = 
  dipoleHelixMultifilar with properties:

             NumArms: 4
              Radius: 0.0220
               Width: 1.0000e-03
               Turns: 3
             Spacing: 0.0350
           ShortEnds: 1
    WindingDirection: 'CCW'
                Tilt: 0
            TiltAxis: [1 0 0]
                Load: [1x1 lumpedElement]

show(ant)

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

ant = dipoleHelixMultifilar('Radius',28e-3,'Width',1.2e-3,'Turns',4);
show(ant)

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

pattern(ant,1.8e9);

Introduced in R2018b