# Documentation

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# yagiUda

Create Yagi-Uda array antenna

## Description

The `yagiUda` class creates a classic Yagi-Uda array comprised of an exciter, reflector, and N- directors along the z-axis. The reflector and directors create a traveling wave structure that results in a directional radiation pattern.

The exciter, reflector, and directors have equal widths and are related to the diameter of an equivalent cylindrical structure by the equation

`$w=2d=4r$`
where:

• d is the diameter of equivalent cylinder

• r is the radius of equivalent cylinder

For a given cylinder radius, use the `cylinder2strip` utility function to calculate the equivalent width. A typical Yagi-Uda antenna array uses folded dipole as an exciter, due to its high impedance. The Yagi-Uda is center-fed and the feed point coincides with the origin. In place of a folded dipole, you can also use a planar dipole as an exciter.

## Creation

### Syntax

``h = yagiUda``
``h = yagiUda(Name,Value)``

### Description

``` `h = yagiUda` creates a half-wavelength Yagi-Uda array antenna along the Z-axis. The default Yagi-Uda uses folded dipole as three directors, one reflector and a folded dipole as an exciter. By default, the dimensions are chosen for an operating frequency of 300 MHz.```

example

``` `h = yagiUda(Name,Value)` creates a half-wavelength Yagi-Uda array antenna, with additional properties specified by one or more name-value pair arguments. `Name` is the property name and `Value` is the corresponding value. You can specify several name-value pair arguments in any order as `Name1`, `Value1`, `...`, `NameN`, `ValueN`. Properties not specified retain default values.```

## Properties

expand all

Antenna Type used as exciter, specified as the comma-separated pair consisting of `'Exciter'` and an object.

Example: `'Exciter',dipole`

Total number of director elements, specified as a scalar.

### Note

Number of director elements should be less than or equal to 20.

Example: `'NumDirectors',13`

Data Types: `double`

Director length, specified as a scalar or vector in meters.

Example: `'DirectorLength',[0.4 0.5]`

Data Types: `double`

Spacing between directors, specified as a scalar or vector in meters.

Example: `'DirectorSpacing',[0.4 0.5]`

Data Types: `double`

Reflector length, specified as a scalar in meters.

Example: `'ReflectorLength',0.3`

Data Types: `double`

Spacing between exciter and reflector, specified as a scalar in meters.

Example: `'ReflectorSpacing', 0.4`

Data Types: `double`

Lumped elements added to the antenna feed, specified as a lumped element object handle. For more information, see `lumpedElement`.

Example: `'Load',lumpedelement`. `lumpedelement` is the object handle for the load created using `lumpedElement`.

Tilt angle of antenna, specified as a scalar or vector with each element unit in degrees.

Example: `'Tilt',90`

Example: `'Tilt',[90 90 0]`

Data Types: `double`

Tilt axis of the antenna, specified as:

• A three-element vector 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 as three-element vectors of Cartesian coordinates. In this case, the antenna rotates along the line joining the two points.

• A string input for simple rotations around the principal planes, X, Y, or Z.

Example: `'TiltAxis',[0 1 0]`

Example: `'TiltAxis',[0 0 0;0 1 0]`

Example: `'TiltAxis','Z'`

Data Types: `double`

## Object Functions

 `show` Display antenna or array structure; Display shape as filled patch `info` Display information about antenna or array `axialRatio` Axial ratio of antenna `beamwidth` Beamwidth of antenna `charge` Charge distribution on metal or dielectric antenna or array surface `current` Current distribution on metal or dielectric antenna or array surface `design` Design prototype antenna for resonance at specified frequency `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 or dielectric antenna or array structure `meshconfig` Change mesh mode of antenna structure `pattern` Radiation pattern 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 `returnLoss` Return loss of antenna; scan return loss of array `sparameters` S-parameter object `vswr` Voltage standing wave ratio of antenna

## Examples

expand all

Create and view a Yagi-Uda array antenna with 13 directors.

```y = yagiUda('NumDirectors',13); show(y)```

Plot radiation pattern of a Yagi-Uda array antenna at a frequency of 30 0MHz.

```y = yagiUda('NumDirectors',13); pattern(y,300e6) ```

Calculate the width of the strip approximation to a cylinder of radius 20 mm.

`w = cylinder2strip(20e-3)`
```w = 0.0800 ```

## References

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