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

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

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 = dipoleHelixMultifilar

ant = dipoleHelixMultifilar(Name,Value)

Description

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.

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.

Properties

NumArms — Number of helical elements

4 (default) | 2

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 — Radius of turns

0.0220 (default) | positive real scalar

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

Example: 'Radius',28e-03

Example: ant.Radius = 28e-03

Data Types: double

Width — Width of strip

1.000e-03 (default) | positive real scalar

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

Example: 'Width',0.2

Example: ant.Width = 0.2

Data Types: double

Turns — Number of turns

3 (default) | scalar integer

Number of turns, specified as a scalar integer.

Example: 'Turns',4

Example: ant.Turns = 4

Data Types: double

Spacing — Spacing between turns

0.0350 (default) | positive real scalar

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

ShortEnds — Status of ends of helix

1 (default) | 0

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

WindingDirection — Direction of helix turns (windings)

'CCW' (default) | 'CW'

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

Example: 'WindingDirection','CW'

Example: ant.WindingDirection = 'CW'

Data Types: char | string

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

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

Load — Lumped elements

[1x1 LumpedElement] (default) | lumped element object handle

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 — Tilt angle of antenna

0 (default) | scalar | vector

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

Example: 'Tilt',90

Example: ant.Tilt = 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.

Note

The wireStack antenna object only accepts the dot method to change its properties.

Data Types: double

TiltAxis — Tilt axis of antenna

[1 0 0] (default) | three-element vector of Cartesian coordinates | two three-element vectors of Cartesian coordinates | 'X' | 'Y' | 'Z'

Tilt axis of the antenna, specified as:

• 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, 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 Antennas and Arrays.

Example: 'TiltAxis',[0 1 0]

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

Example: ant.TiltAxis = 'Z'

Note

The wireStack antenna object only accepts the dot method to change its properties.

Data Types: double

Object Functions

show	Display antenna or array structure; display shape as filled patch
axialRatio	Axial ratio of antenna
beamwidth	Beamwidth of antenna
charge	Charge distribution on metal or dielectric antenna or array surface
current	Current distribution on metal or dielectric antenna or array surface
design	Design prototype antenna or arrays for resonance at specified frequency
efficiency	Radiation efficiency of antenna
EHfields	Electric and magnetic fields of antennas; Embedded electric and magnetic fields of antenna element in arrays
impedance	Input impedance of antenna; scan impedance of array
mesh	Mesh properties of metal or dielectric antenna or array structure
meshconfig	Change mesh mode of antenna structure
optimize	Optimize antenna or array using SADEA optimizer
pattern	Radiation pattern and phase of antenna or array; Embedded pattern of antenna element in array
patternAzimuth	Azimuth pattern of antenna or array
patternElevation	Elevation pattern of antenna or array
returnLoss	Return loss of antenna; scan return loss of array
sparameters	S-parameter object
vswr	Voltage standing wave ratio of antenna

Examples

Default Multifilar Helical Dipole Antenna

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'
           Conductor: [1x1 metal]
                Tilt: 0
            TiltAxis: [1 0 0]
                Load: [1x1 lumpedElement]

show(ant)

Quadrafilar Helical Dipole Antenna and Radiation Pattern

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);