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physconst

Physical constants

Syntax

`Const = physconst(Name)`

Description

`Const = physconst(Name)` returns the constant specified in the `Name` argument. Valid values are `'LightSpeed'`, `'Boltzmann'`, or `'EarthRadius'`. Values are in SI units.

Input Arguments

 `Name` Character vector that indicates which physical constant the function returns. Values are not case sensitive.

Output Arguments

 `Const` Value of physical constant specified in the input argument `Name`.

Definitions

The following table lists the supported constants and their values in SI units.

ConstantDescriptionValue
`'LightSpeed'`Speed of light in vacuum299,792,458 m/s. Most commonly denoted by c.
`'Boltzmann'`Boltzmann constant relating energy to temperature$1.38×{10}^{-23}$ J/K. Most commonly denoted by k.
`'EarthRadius'`Mean radius of the Earth6,371,000 m

Examples

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Determine the wavelength of a 1 Ghz electromagnetic wave.

```freq = 1e9; lambda = physconst('LightSpeed')/freq ```
```lambda = 0.2998 ```

Approximate the thermal noise power per unit bandwidth in the I and Q channels of a receiver.

Specify the receiver temperature and Boltzmann constant.

```T = 290; k = physconst('Boltzmann'); ```

Compute the noise power per unit bandwidth, split evenly between the in-phase and quadrature channels.

```Noise_power = 10*log10(k*T/2); ```