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Create Archimedean spiral antenna


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:



  • 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.



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

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MATLAB object, returned as scalar spiralArchimedean object.


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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

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

Example: 'Turns',2

Example: ant.Turns = 2

Data Types: double

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

Example: 'InnerRadius',1e-3

Example: ant.InnerRadius = 1e-3

Data Types: double

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

Example: 'OuterRadius',1e-3

Example: ant.OuterRadius = 1e-3

Data Types: double

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

Example: 'WindingDirection','CW'

Example: ant.WindingDirection = CW

Data Types: char | string

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 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 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.


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

Data Types: double

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

showDisplay antenna, array structures or shapes
infoDisplay information about antenna or array
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
efficiencyRadiation efficiency of antenna
EHfieldsElectric and magnetic fields of antennas; Embedded electric and magnetic fields of antenna element in arrays
impedanceInput impedance of antenna; scan impedance of array
meshMesh properties of metal, dielectric antenna, or array structure
meshconfigChange mesh mode of antenna structure
optimizeOptimize antenna or array using SADEA optimizer
patternRadiation pattern and phase of antenna or array; Embedded pattern of antenna element in array
patternAzimuthAzimuth pattern of antenna or array
patternElevationElevation pattern of antenna or array
rcsCalculate and plot radar cross section (RCS) of platform, antenna, or array
returnLossReturn loss of antenna; scan return loss of array
sparametersCalculate S-parameter for antenna and antenna array objects
vswrVoltage standing wave ratio of antenna


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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);

Figure contains an axes object. The axes object with title spiralArchimedean antenna element, xlabel x (mm), ylabel y (mm) contains 3 objects of type patch, surface. These objects represent PEC, feed.

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));

Figure contains an axes object. The axes object with title Impedance, xlabel Frequency (GHz), ylabel Impedance (ohms) contains 2 objects of type line. These objects represent Resistance, Reactance.

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]


Figure contains an axes object. The axes object with title spiralArchimedean antenna element, xlabel x (mm), ylabel y (mm) contains 3 objects of type patch, surface. These objects represent PEC, feed.


[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