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 resonating around 1.575 GHz. 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

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

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

ant = helixMultifilar

ant = helixMultifilar(Name=Value)

Description

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 dimensions are chosen for an operating frequency of around 1.575 GHz.

ant = helixMultifilar(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.

For example, ant = helixMultifilar(Radius=28e-03) creates a multifilar helix with turns of radius 28e-03 m.

Properties

NumArms — Number of helical elements

4 (default) | 2

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: 2

Data Types: double

Radius — Radius of turns

0.0220 (default) | positive scalar integer | two-element vector

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: 28e-03

Data Types: double

Width — Width of strip

1000e-03 (default) | positive scalar integer

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

Example: 0.2

Data Types: double

Turns — Number of turns

3 (default) | scalar integer

Number of turns, specified as a scalar integer.

Example: 4

Data Types: double

Spacing — Spacing between turns

0.0350 (default) | positive scalar integer

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

Example: 7.5e-2

Data Types: double

ShortEnds — Status of helix ends

0 (default) | 1

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: 1

Data Types: double

WindingDirection — Direction of helix turns (windings)

"CCW" (default) | "CW"

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

Example: "CW"

Data Types: string

FeedStubHeight — Height of feeding stub from ground plane

1.000e-03 (default) | positive scalar integer

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

Example: 7.5e-2

Data Types: double

GroundPlaneRadius — Ground plane radius

0.0750 (default) | positive scalar integer

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: 2.05

Data Types: double

FeedVoltage — Excitation voltage applied to individual antenna feeds

1 (default) | scalar integer | vector integers

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: [1 2]

Data Types: double

FeedPhase — Excitation voltage phase applied to individual antenna feeds

0 (default) | scalar integer | vector integers

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: [0 45]

Data Types: double

Substrate — Type of dielectric material

dielectric("Air") (default) | dielectric object

Type of dielectric material used as a substrate, specified as a dielectric object. You can choose any dielectric material from the DielectricCatalog or specify a dielectric material of your choice. 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 on dielectric substrate meshing, see Meshing.

Example: dielectric("FR4")

Conductor — Type of metal

metal("PEC") (default) | metal object

Type of the metal used as a conductor, specified as a metal object. You can choose any metal from the MetalCatalog or specify a metal of your choice. For more information on metal conductor meshing, see Meshing.

Example: metal("Copper")

Load — Lumped elements

[1x1 lumpedElement] (default) | lumpedElement object

Lumped elements added to the antenna feed, specified as a lumpedElement object. You can add a load anywhere on the surface of the antenna. By default, the load is at the feed.

Example: Load=lumpedElement(Impedance=75)

Example: antenna.Load = lumpedElement(Impedance=75)

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 plot axial ratio of antenna or array
bandwidth	Calculate and plot absolute bandwidth of antenna or array
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	Calculate and plot radiation efficiency of antenna or array
EHfields	Electric and magnetic fields of antennas or embedded electric and magnetic fields of antenna element in arrays
feedCurrent	Calculate current at feed for antenna or array
impedance	Calculate and plot 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
msiwrite	Write antenna or array analysis data to MSI planet file
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
peakRadiation	Calculate and mark maximum radiation points of antenna or array on radiation pattern
rcs	Calculate and plot monostatic and bistatic radar cross section (RCS) of platform, antenna, or array
returnLoss	Calculate and plot return loss of antenna or scan return loss of array
show	Display antenna, array structures, shapes, or platform
sparameters	Calculate S-parameters for antenna or array
stlwrite	Write mesh information to STL file
vswr	Calculate and plot voltage standing wave ratio (VSWR) of antenna or array element

Examples

Quadrafilar Helix

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)

Bifilar Helix

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)

Radiation Pattern of Conical Multifilar Helix Antenna

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)

Plot the pattern of the antenna at 3 GHz.

pattern(ant,3e9)

Overlay the antenna on the pattern.

Quadfilar Helix Antenna with Dielectric Substrate

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)

Version History

Introduced in R2018b