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.```

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`

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 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`

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.

Example: `[0 1 0]`

Example: `[0 0 0;0 1 0]`

Example: `"Z"`

Data Types: `double` | `string`

Object Functions

 `axialRatio` Calculate and/or plot axial ratio of antenna or array `bandwidth` Calculate and/or plot absolute bandwidth 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 or create AI-based antenna from antenna catalog objects `efficiency` Radiation efficiency of antenna `EHfields` Electric and magnetic fields of antennas or embedded electric and magnetic fields of antenna element in arrays `impedance` 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` Mesh properties of metal, dielectric antenna, or array structure `meshconfig` Change meshing mode of antenna, array, custom antenna, custom array, or custom geometry `optimize` Optimize antenna or array using SADEA optimizer `pattern` Plot radiation pattern and phase of antenna or array or embedded pattern of antenna element in array `patternAzimuth` Azimuth plane radiation pattern of antenna or array `patternElevation` Elevation plane radiation pattern of antenna or array `rcs` Calculate and plot monostatic and bistatic radar cross section (RCS) of platform, antenna, or array `resonantFrequency` Calculate and/or plot resonant frequency of antenna `returnLoss` Return loss of antenna or scan return loss of array `show` Display antenna, array structures, shapes, or platform `sparameters` Calculate S-parameters for antennas and antenna arrays `vswr` Voltage standing wave ratio (VSWR) of antenna or array element

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' 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