spiralArchimedean

Create Archimedean spiral antenna

Description

The spiralArchimedean object creates a planar Archimedean spiral antenna on the xy- plane. The default Archimedean spiral is always center fed and has two arms. The field characteristics of this antenna are frequency independent. A realizable spiral has finite limits on the feeding region and the outermost point of any arm of the spiral. The spiral antenna exhibits a broadband behavior. The outer radius imposes the low frequency limit and the inner radius imposes the high frequency limit. The arm radius grows linearly as a function of the winding angle.

The equation of the Archimedean spiral is:

$$r=r_0+a\varphi$$

where:

• r₀ is the inner radius

• a is the growth rate

• ϕ is the winding angle of the spiral

Archimedean spiral antenna is a self-complementary structure, where the spacing between the arms and the width of the arms are equal. The default antenna is center fed. The feed point coincides with the origin. The origin is in the xy- plane.

Creation

Syntax

ant = spiralArchimedean

ant = spiralArchimedean(Name,Value)

Description

ant = spiralArchimedean creates a planar Archimedean spiral on the X-Y plane. By default, the antenna operates over a broadband frequency range of 3–5 GHz.

ant = spiralArchimedean(Name,Value) sets properties using one or more name-value pairs. For example, ant = spiralArchimedean('Turns',6.25) creates a Archimedean spiral of 6.25 turns.

Output Arguments

ant — MATLAB object

scalar spiralArchimedean object (default)

MATLAB object, returned as scalar spiralArchimedean object.

Properties

NumArms — Number of arms

2 (default) | scalar integer

Number of arms, specified as a scalar integer. You can also create a single arm Archimedean spiral by specifying NumArms is equal to one.

Example: 'NumArms',1

Example: ant.NumArms = 1

Data Types: double

Turns — Number of turns of spiral antenna

1.5000 (default) | scalar

Number of turns of the spiral antenna, specified as a scalar.

Example: 'Turns',2

Example: ant.Turns = 2

Data Types: double

InnerRadius — Inner radius of spiral antenna

5.0000e-04 (default) | scalar

inner radius of the spiral antenna, specified as a scalar in meters.

Example: 'InnerRadius',1e-3

Example: ant.InnerRadius = 1e-3

Data Types: double

OuterRadius — Outer radius of spiral antenna

0.0398 (default) | scalar

Outer radius of the spiral antenna, specified as a scalar in meters.

Example: 'OuterRadius',1e-3

Example: ant.OuterRadius = 1e-3

Data Types: double

WindingDirection — Direction of spiral turns (windings)

'CW' | 'CCW'

Direction of the spiral 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

Lumped elements added to the spiral antenna feed, specified as a lumped element object. You can add a load anywhere on the surface of the antenna. By default, it 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 Archimedean Spiral Antenna

Create and view a 2-turn Archimedean spiral antenna with a 1 mm starting radius and 40 mm outer radius.

sa = spiralArchimedean('Turns',2, 'InnerRadius',1e-3, 'OuterRadius',40e-3);
show(sa)

Impedance of Archimedean Spiral Antenna

Calculate the impedance of an Archimedean spiral antenna over a frequency range of 1-5 GHz.

sa = spiralArchimedean('Turns',2, 'InnerRadius',1e-3, 'OuterRadius',40e-3);
impedance(sa, linspace(1e9,5e9,21));

Single-Arm Archimedean Spiral

Create and view a single-arm Archimedean spiral.

ant = spiralArchimedean;
ant.NumArms = 1

ant = 
  spiralArchimedean with properties:

             NumArms: 1
               Turns: 1.5000
         InnerRadius: 5.0000e-04
         OuterRadius: 0.0398
    WindingDirection: 'CCW'
           Conductor: [1x1 metal]
                Tilt: 0
            TiltAxis: [1 0 0]
                Load: [1x1 lumpedElement]

show(ant)

References

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

[2] Nakano, H., Oyanagi, H. and Yamauchi, J. “A Wideband Circularly Polarized Conical Beam From a Two-Arm Spiral Antenna Excited in Phase”. IEEE Transactions on Antennas and Propagation. Vol. 59, No. 10, Oct 2011, pp. 3518-3525.

[3] Volakis, John. Antenna Engineering Handbook, 4th Ed. McGraw-Hill

Version History

Introduced in R2015a