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helixMultifilar

Creates bifilar or quadrafilar helix or conical helix antenna on circular ground plane

Description

The helixMultifilar object creates a bifilar or quadrafilar helix or conical helix antenna on a circular ground plane. You can create both short-circuited and open-ended 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 xy- plane. Helix antennas are commonly used 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

Description

example

ant = helixMultifilar creates a bifilar or quadrafilar helix or conical helix antenna operating in the axial mode. The default multifilar helical antenna is end-fed and has a circular ground plane on the xy- plane. The default operating frequency is around 2 GHz.

example

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

Properties

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Number of helical elements, specified as 4 or 2. Specify two elements to create a bifilar helix antenna, and four elements to create a quadrafilar helix antenna.

Example: 'NumArms',2

Example: ant.NumArms = 2

Data Types: double

Radius of the turns, specified as a positive scalar integer in meters or a two element vector with each element unit in meters. In the two-element vector, the first element specifies the bottom radius and the second element specifies the top radius of the conical helix antenna.

Example: 'Radius',28e-03

Example: ant.Radius = 28e-03

Data Types: double

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

Example: 'Spacing',7.5e-2

Example: ant.Spacing = 7.5e-2

Data Types: double

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

Example: 'ShortEnds',1

Example: ant.ShortEnds = 1

Data Types: double

Direction of the helix turns (windings), specified as 'CW' for clockwise or 'CCW' for counter-clockwise.

Example: 'WindingDirection','CW'

Example: ant.WindingDirection = 'CW'

Data Types: char | string

Height of the feeding stub from the ground plane, specified as a positive scalar integer in meters.

Example: 'FeedStubHeight',7.5e-2

Example: ant.FeedStubHeight = 7.5e-2

Data Types: double

Ground plane radius, specified as a positive scalar integer in meters. By default, the ground plane is on the xy- plane and is symmetrical about the origin.

Setting this value to Inf uses the infinite ground plane technique for antenna analysis.

Example: 'GroundPlaneRadius',2.05

Example: ant.GroundPlaneRadius = 7.5e-2

Data Types: double

Excitation voltage applied to individual antenna feeds, specified as a scalar integer or vector integers. A scalar value applies the same voltage to all feeds.

Example: 'FeedVoltage',[1 2]

Example: ant.FeedVoltage = [1 2]

Data Types: double

Excitation voltage phase applied to individual antenna feeds, specified as a scalar integer or vector integers. A scalar value applies the same voltage phase to all feeds.

Example: 'FeedPhase',[0 45]

Example: ant.FeedPhase = [0 45]

Data Types: double

Type of dielectric material used as the substrate, specified as a dielectric object. You can specify only one dielectric layer in the helixMultifilar object. When using the Substrate property, specify the same radius for all the turns. When using a dielectric material other than air, the number of turns in the helix should be greater than 1. For more information, see dielectric. For more information on dielectric substrate meshing, see Meshing.

Example: d = dielectric('FR4'); ant = helixMultifilar('Substrate',d)

Example: d = dielectric('FR4'); ant.Substrate = d;

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: m = metal('Copper'); 'Conductor',m

Example: m = metal('Copper'); ant.Conductor = m

Lumped elements added to the antenna feed, specified as a lumped element object. 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 for the load created using lumpedElement.

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

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.

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

showDisplay antenna, array structures, shapes, or platform
axialRatioAxial ratio of antenna
beamwidthBeamwidth of antenna
chargeCharge distribution on antenna or array surface
currentCurrent distribution on antenna or array surface
designDesign prototype antenna or arrays for resonance around specified frequency or create AI-based antenna from antenna catalog objects
efficiencyRadiation efficiency of antenna
EHfieldsElectric and magnetic fields of antennas or embedded electric and magnetic fields of antenna element in arrays
impedanceInput impedance of antenna or scan impedance of array
meshMesh properties of metal, dielectric antenna, or array structure
meshconfigChange meshing mode of antenna, array, custom antenna, custom array, or custom geometry
optimizeOptimize antenna or array using SADEA optimizer
patternPlot radiation pattern and phase of antenna or array or embedded pattern of antenna element in array
patternAzimuthAzimuth plane radiation pattern of antenna or array
patternElevationElevation plane radiation pattern of antenna or array
rcsCalculate and plot radar cross section (RCS) of platform, antenna, or array
returnLossReturn loss of antenna or scan return loss of array
sparametersCalculate S-parameters for antennas and antenna arrays
vswrVoltage standing wave ratio (VSWR) of antenna or array element

Examples

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Create and view a Quadrafilar helix antenna.

ant = helixMultifilar
ant = 
  helixMultifilar with properties:

              NumArms: 4
               Radius: 0.0220
                Width: 1.0000e-03
                Turns: 3
              Spacing: 0.0350
            ShortEnds: 0
     WindingDirection: 'CCW'
       FeedStubHeight: 1.0000e-03
    GroundPlaneRadius: 0.0750
          FeedVoltage: 1
            FeedPhase: 0
            Substrate: [1x1 dielectric]
            Conductor: [1x1 metal]
                 Tilt: 0
             TiltAxis: [1 0 0]
                 Load: [1x1 lumpedElement]

show(ant)

Figure contains an axes object. The axes object with title helixMultifilar antenna element, xlabel x (mm), ylabel y (mm) contains 10 objects of type patch, surface. These objects represent PEC, feed.

Create and view a bifilar helix antenna.

ant=helixMultifilar('NumArms',2)
ant = 
  helixMultifilar with properties:

              NumArms: 2
               Radius: 0.0220
                Width: 1.0000e-03
                Turns: 3
              Spacing: 0.0350
            ShortEnds: 0
     WindingDirection: 'CCW'
       FeedStubHeight: 1.0000e-03
    GroundPlaneRadius: 0.0750
          FeedVoltage: 1
            FeedPhase: 0
            Substrate: [1x1 dielectric]
            Conductor: [1x1 metal]
                 Tilt: 0
             TiltAxis: [1 0 0]
                 Load: [1x1 lumpedElement]

show(ant)

Figure contains an axes object. The axes object with title helixMultifilar antenna element, xlabel x (mm), ylabel y (mm) contains 6 objects of type patch, surface. These objects represent PEC, feed.

Create and view a conical multifilar helix antenna of radii, 0.0220 m and 0.00800 m respectively.

ant = helixMultifilar('Radius',[0.0080,0.0220],'ShortEnds',1)
ant = 
  helixMultifilar with properties:

              NumArms: 4
               Radius: [0.0080 0.0220]
                Width: 1.0000e-03
                Turns: 3
              Spacing: 0.0350
            ShortEnds: 1
     WindingDirection: 'CCW'
       FeedStubHeight: 1.0000e-03
    GroundPlaneRadius: 0.0750
          FeedVoltage: 1
            FeedPhase: 0
            Substrate: [1x1 dielectric]
            Conductor: [1x1 metal]
                 Tilt: 0
             TiltAxis: [1 0 0]
                 Load: [1x1 lumpedElement]

show(ant)

Figure contains an axes object. The axes object with title helixMultifilar antenna element, xlabel x (mm), ylabel y (mm) contains 12 objects of type patch, surface. These objects represent PEC, feed.

Plot the pattern of the antenna at 3 GHz.

pattern(ant,3e9)

Figure contains an axes object and other objects of type uicontrol. The axes object contains 12 objects of type patch, surface.

Overlay the antenna on the pattern.

Create a custom quadfilar helix antenna with a FR4 dielectric substrate.

d = dielectric('FR4'); 
ant = helixMultifilar('Radius',22e-3 ,'NumArms',4,'Width',1e-3, 'Turns',3, 'Spacing',35e-3 ,'FeedStubHeight',1e-3, 'Substrate', d)
ant = 
  helixMultifilar with properties:

              NumArms: 4
               Radius: 0.0220
                Width: 1.0000e-03
                Turns: 3
              Spacing: 0.0350
            ShortEnds: 0
     WindingDirection: 'CCW'
       FeedStubHeight: 1.0000e-03
    GroundPlaneRadius: 0.0750
          FeedVoltage: 1
            FeedPhase: 0
            Substrate: [1x1 dielectric]
            Conductor: [1x1 metal]
                 Tilt: 0
             TiltAxis: [1 0 0]
                 Load: [1x1 lumpedElement]

View quadfilar helix antenna.

show(ant)

Figure contains an axes object. The axes object with title helixMultifilar antenna element, xlabel x (mm), ylabel y (mm) contains 12 objects of type patch, surface. These objects represent PEC, feed, FR4.

Version History

Introduced in R2018b