# ap2beamwidth

Compute half-power beamwidth from aperture length

Since R2021a

## Syntax

``rlhpbw = ap2beamwidth(d,lambda)``
``rlhpbw = ap2beamwidth(d,lambda,azb)``

## Description

````rlhpbw = ap2beamwidth(d,lambda)` computes the half-power, one-way beamwidth,`rlhpbw` for a real aperture. The quantity `d` specifies the length of an unweighted antenna and `lambda` specifies the radar wavelength.```

example

````rlhpbw = ap2beamwidth(d,lambda,azb)` also specifies the azimuth impulse broadening factor `azb`.```

example

## Examples

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Estimate the half-power beamwidths of side-looking airborne radars, each operating at wavelengths of 1, 2, and 3 centimeters. The radars have antenna aperture sizes of 2 and 3 meters in the azimuth direction.

```lambda = [1,2,3]*1e-2; daz = [2,3]; hpbw = ap2beamwidth(daz,lambda)```
```hpbw = 2×3 0.2865 0.5730 0.8594 0.1910 0.3820 0.5730 ```

Estimate the half-power beamwidth of a radar operating at a wavelength of 2 cm. The radar has an antenna aperture dimension of 2 m in the azimuth direction. Use an azimuth broadening factor of 1.5.

```lambda = 2e-2; daz = 2; azbf = 1.5; hpbw = ap2beamwidth(daz,lambda,azbf)```
```hpbw = 0.8594 ```

## Input Arguments

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Length of unweighted antenna, specified as a positive scalar or length-J vector of positive values. Units are in meters.

Example: `[3,4]`[

Data Types: `double`

Radar wavelength, specified as a positive real scalar or a length-K vector of real values.

Example: `1.5`

Data Types: `double`

Azimuth impulse broadening factor, specified as a positive real scalar. Broadening is due to data weighting or windowing for side lobe control. The quantity is the actual –3 dB main lobe width with respect to the nominal width. Typical window functions such as `hamming` or `hann` exhibit azimuth impulse broadening factors in the range of 1 to 1.5.

Example: `1.2`

Data Types: `double`

## Output Arguments

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Half-power one-way beamwidth, specified as a positive scalar or as a J-by-K real-valued vector of positive values. Matrix rows correspond to the length of `d` and columns correspond to the length of `lambda`. Units are in degrees.

## Algorithms

The half-power beamwidth (in degrees) for a rectangular aperture is 180λ/πd where λ is the radar wavelength and d is the aperture length. The azimuth broadening factor b multiplies the beamwidth to produce a half-power beamwidth of 180bλ/πd.

## Version History

Introduced in R2021a