spiralArchimedean

Create Archimedean spiral antenna

Description

The spiralArchimedean object creates a planar Archimedean spiral antenna on the X-Y 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=r0+aϕ

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-complimentary 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 X-Y plane.

Creation

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.

example

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.

Properties

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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

Lumped elements added to the spiral antenna feed, specified as a lumped element object handle. 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 handle 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 degree about two axes, defined by vectors.

Data Types: double

Tilt axis of the antenna, specified as:

  • Three-element vectors of Cartesian coordinates in meters. In this case, each 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'

Object Functions

showDisplay antenna or array structure; Display shape as filled patch
infoDisplay information about antenna or array
axialRatioAxial ratio of antenna
beamwidthBeamwidth of antenna
chargeCharge distribution on metal or dielectric antenna or array surface
currentCurrent distribution on metal or dielectric antenna or array surface
designDesign prototype antenna or arrays for resonance at specified frequency
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 or dielectric antenna or array structure
meshconfigChange mesh mode of antenna structure
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
returnLossReturn loss of antenna; scan return loss of array
sparametersS-parameter object
vswrVoltage standing wave ratio of antenna

Examples

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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);
show(sa)

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));

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'
                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

Introduced in R2015a