helix

Create helix or conical helix antenna on ground plane

Description

Use the helix object to create a helix or conical helix antenna on a circular ground plane. The helix antenna is a common choice in satellite communication.

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. Commonly, helix antennas are 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 equation for the helix is

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

where

• r is the radius of the helix.

• 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.

Note

In an array of helix antennas, the circular ground plane of the helix is converted to rectangular ground plane.

Creation

Syntax

ant = helix

ant = helix(Name,Value)

Description

ant = helix creates a helix antenna operating in axial mode. The default antenna operates around 2 GHz.

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

Output Arguments

ant — Helix antenna

helix object

Helix antenna, returned as a helix object.

Properties

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: 'Radius',[28e-03 30e-03]

Example: ant.Radius = [28e-03 30e-03]

Data Types: double

Width — Strip width

1.0000e-03 (default) | scalar

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

Example: ant.Width = 5

Data Types: double

Turns — Number of turns of helix

3 (default) | scalar

Number of turns of the helix, specified as a scalar.

Example: 'Turns',2

Example: ant.Turns = 2

Data Types: double

Spacing — Spacing between turns

0.0350 (default) | scalar

Spacing between turns, specified as a scalar in meters.

Example: 'Spacing',1.5

Example: ant.Spacing = 1.5

Data Types: double

WindingDirection — Direction of helix turns (windings)

'CW' | 'CCW'

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

Example: 'WindingDirection',CW

Example: ant.WindingDirection = CW

Data Types: char | string

GroundPlaneRadius — Ground plane radius

0.0750 (default) | scalar in meters

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

Example: 'GroundPlaneRadius',2.05

Example: ant.GroundPlaneRadius = 2.05

Data Types: double

FeedStubHeight — Feeding stub height from ground

1.0000e-03 (default) | scalar

Feeding stub height from ground, specified as a scalar in meters.

Example: 'FeedStubHeight',2.000e-03

Example: ant.FeedStubHeight = 2.000e-03

Note

The default value is chosen to allow backward compatibility.

Data Types: double

Substrate — Type of dielectric material

'Air' (default) | dielectric object

Type of dielectric material used as the substrate, specified as a dielectric object. You can specify only one dielectric layer in the helix 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('Teflon'); hx = helix('Substrate',d)

Example: d = dielectric('Teflon'); hx.Substrate = d

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

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 — 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: 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: TiltAxis = 'Z'

Data Types: double

Object Functions

show	Display antenna, array structures or shapes
info	Display information about antenna or array
axialRatio	Axial ratio of antenna
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
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, 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
rcs	Calculate and plot radar cross section (RCS) of platform, antenna, or array
returnLoss	Return loss of antenna; scan return loss of array
sparameters	Calculate S-parameter for antenna and antenna array objects
vswr	Voltage standing wave ratio of antenna

Examples

Create and View Helix Antenna

Create and view a helix antenna that has a 28 mm turn radius, 1.2 mm strip width, and 4 turns.

hx = helix('Radius',28e-3,'Width',1.2e-3,'Turns',4)

hx = 
  helix with properties:

               Radius: 0.0280
                Width: 0.0012
                Turns: 4
              Spacing: 0.0350
     WindingDirection: 'CCW'
       FeedStubHeight: 1.0000e-03
    GroundPlaneRadius: 0.0750
            Substrate: [1x1 dielectric]
            Conductor: [1x1 metal]
                 Tilt: 0
             TiltAxis: [1 0 0]
                 Load: [1x1 lumpedElement]

show(hx)

Radiation Pattern of Helix Antenna

Plot the radiation pattern of a helix antenna.

hx = helix('Radius',28e-3,'Width',1.2e-3,'Turns',4);
pattern(hx,1.8e9);

Calculate Spacing of Helix Antenna with Varying Radius

Calculate the spacing of a helix that has a pitch of 12 degrees and a radius that varies from 20 mm to 22 mm in steps of 0.5 mm.

s = helixpitch2spacing(12,20e-3:0.5e-3:22e-3)

s = 1×5

    0.0267    0.0274    0.0280    0.0287    0.0294

Radiation Pattern of Helix Antenna

Plot the radiation pattern of a helix antenna with transparency specified as 0.5.

p = PatternPlotOptions

p = 
  PatternPlotOptions with properties:

      Transparency: 1
         SizeRatio: 0.9000
    MagnitudeScale: []
     AntennaOffset: [0 0 0]

p.Transparency = 0.5;
ant = helix;
pattern(ant,2e9,'patternOptions',p)

To understand the effect of Transparency, chose Overlay Antenna in the radiation pattern plot.

This option overlays the helix antenna on the radiation pattern.

Helix Antenna with Dielectric Substrate

Create a custom helix antenna with a Teflon dielectric substrate.

d = dielectric('Teflon'); 
hx = helix('Width',0.815e-3,'Turns',6,'Radius',9.3e-3,'Spacing',12.4e-3,'Substrate',d)

hx = 
  helix with properties:

               Radius: 0.0093
                Width: 8.1500e-04
                Turns: 6
              Spacing: 0.0124
     WindingDirection: 'CCW'
       FeedStubHeight: 1.0000e-03
    GroundPlaneRadius: 0.0750
            Substrate: [1x1 dielectric]
            Conductor: [1x1 metal]
                 Tilt: 0
             TiltAxis: [1 0 0]
                 Load: [1x1 lumpedElement]

View the helix antenna.

show(hx)

References

[1] Balanis, C.A. Antenna Theory. Analysis and Design, 3rd Ed. New York: Wiley, 2005.

[2] Volakis, John. Antenna Engineering Handbook, 4th Ed. New York: Mcgraw-Hill, 2007.

[3] Zhang, Yan, Q. Ding, J. Chen, S. Lu, Z. Zhu and L. L. Cheng. “A Parametric Study of Helix Antenna for S-Band Satellite Communications.” 9th International Symposium on Antenna Propagation and EM Theory (ISAPE). 2010, pp. 193–196.

[4] Djordjevic, A.R., Zajic, A.G., Ilic, M. M., Stuber, G.L. “Optimization of Helical antennas (Antenna Designer's Notebook)” IEEE Antennas and Propagation Magazine. December, 2006, pp. 107, pp.115.

[5] B. Young, K. A. O'Connor and R. D. Curry, “Reducing the size of helical antennas by means of dielectric loading,” 2011 IEEE Pulsed Power Conference, 2011, pp. 575-579, doi: 10.1109/PPC.2011.6191490

Version History

Introduced in R2015a