# vswr

Calculate and plot voltage standing wave ratio (VSWR) of antenna or array element

## Syntax

``vswr(object,frequency,z0)``
``vswRatio = vswr(object,frequency,z0)``
``vswRatio = vswr(___,UseParallel = true)``

## Description

````vswr(object,frequency,z0)` calculates and plots the VSWR of an antenna or an array element, over specified frequency range, and a reference impedance of `z0` ohms.```

example

````vswRatio = vswr(object,frequency,z0)` calculates and returns the VSWR of an antenna or array element, over specified frequency range, and a reference impedance of `z0` ohms.```

example

````vswRatio = vswr(___,UseParallel = true)` uses the Parallel Computing Toolbox™ to perform VSWR calculations for each frequency in parallel. To use this feature, you need a license to the Parallel Computing Toolbox.```

## Examples

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Plot vswr (voltage standing wave ratio) of a circular loop antenna.

```h = loopCircular; vswr(h,50e6:1e6:100e6,50)```

Calculate vswr (voltage standing wave ratio) of a helix antenna.

```h = helix; hvswr = vswr(h,2e9:1e9:4e9,50)```
```hvswr = 1×3 3.6047 6.7230 3.3524 ```

## Input Arguments

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Antenna or array to calculate the VSWR, specified as one of the following options:

Example: `dipole`

Frequency to calculate the VSWR, specified as a scalar for a single frequency or a vector for a frequency range in Hertz.

Example: `75e6`

Example: `50e6:1e6:100e6`

Data Types: `double`

Reference impedance, specified as a scalar in ohms.

Option to enable parallel pool, specified as a logical value. The default value is `false`. Set the flag to `true` or `1` to enable the parallel pool. Use parallel pool to speedup the VSWR calculations at multiple frequencies for computationally large antennas and arrays.

Example: `UseParallel=true`

Data Types: `logical`

## Output Arguments

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Voltage standing wave ratio, returned as a scalar in dB for a single analysis frequency and a vector in dB for analysis over a frequency range.

## Version History

Introduced in R2015a