spiralArchimedean

Create Archimedean spiral antenna

Description

The default spiralArchimedean object creates a planar Archimedean spiral antenna on the xy- plane resonating around 1.46 GHz. 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(PropertyName=Value)

Description

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

ant = spiralArchimedean(PropertyName=Value) sets properties using one or more name–value arguments. PropertyName is the property name and Value is the corresponding value. You can specify several name-value arguments in any order as PropertyName1=Value1,...,PropertyNameN=ValueN. Properties that you do not specify, retain their default values.

For example, ant = spiralArchimedean(Turns=6.25) creates a Archimedean spiral of 6.25 turns.

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: 1

Data Types: double

Turns — Number of turns of spiral antenna

1.5 (default) | scalar

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

Example: 2

Data Types: double

InnerRadius — Inner radius of spiral antenna

5e-4 (default) | scalar

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

Example: 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: 1e-3

Data Types: double

WindingDirection — Direction of spiral turns (windings)

"CCW" (default) | "CW"

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

Example: "CW"

Data Types: string

Conductor — Type of metal

metal("PEC") (default) | metal object

Type of the metal used as a conductor, specified as a metal object. You can choose any metal from the MetalCatalog or specify a metal of your choice. For more information on metal conductor meshing, see Meshing.

Example: metal("Copper")

Load — Lumped elements

[1x1 lumpedElement] (default) | lumpedElement object

Lumped elements added to the antenna feed, specified as a lumpedElement object. You can add a load anywhere on the surface of the antenna. By default, the load is at the feed.

Example: lumpedElement(Impedance=75)

Tilt — Tilt angle of antenna

0 (default) | scalar | vector

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

Example: 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.

Data Types: double

TiltAxis — Tilt axis of antenna

[1 0 0] (default) | three-element vector | 2-by-3 matrix | "X" | "Y" | "Z"

Tilt axis of the antenna, specified as one of these values:

• 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, specified as a 2-by-3 matrix corresponding to two three-element vectors of Cartesian coordinates. In this case, the antenna rotates around the line joining the two points.

• "x", "y", or "z" to describe a rotation about the x-, y-, or z-axis, respectively.

For more information, see Rotate Antennas and Arrays.

Example: [0 1 0]

Example: [0 0 0;0 1 0]

Example: "Z"

Data Types: double | string

Object Functions

axialRatio	Calculate and plot axial ratio of antenna or array
bandwidth	Calculate and plot absolute bandwidth of antenna or array
beamwidth	Beamwidth of antenna
charge	Charge distribution on antenna or array surface
current	Current distribution on antenna or array surface
design	Create antenna, array, or AI-based antenna resonating at specified frequency
efficiency	Calculate and plot radiation efficiency of antenna or array
EHfields	Electric and magnetic fields of antennas or embedded electric and magnetic fields of antenna element in arrays
feedCurrent	Calculate current at feed for antenna or array
impedance	Calculate and plot input impedance of antenna or scan impedance of array
info	Display information about antenna, array, or platform
memoryEstimate	Estimate memory required to solve antenna or array mesh
mesh	Generate and view mesh for antennas, arrays, and custom shapes
meshconfig	Change meshing mode of antenna, array, custom antenna, custom array, or custom geometry
msiwrite	Write antenna or array analysis data to MSI planet file
optimize	Optimize antenna and array catalog elements using SADEA or TR-SADEA algorithm
pattern	Plot radiation pattern of antenna, array, or embedded element of array
patternAzimuth	Azimuth plane radiation pattern of antenna or array
patternElevation	Elevation plane radiation pattern of antenna or array
peakRadiation	Calculate and mark maximum radiation points of antenna or array on radiation pattern
rcs	Calculate and plot monostatic and bistatic radar cross section (RCS) of platform, antenna, or array
resonantFrequency	Calculate and plot resonant frequency of antenna
returnLoss	Calculate and plot return loss of antenna or scan return loss of array
show	Display antenna, array structures, shapes, or platform
sparameters	Calculate S-parameters for antenna or array
stlwrite	Write mesh information to STL file
vswr	Calculate and plot voltage standing wave ratio (VSWR) of antenna or array element

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: [1×1 metal]
                Tilt: 0
            TiltAxis: [1 0 0]
                Load: [1×1 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