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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 temperature1.38×1023 J/K. Most commonly denoted by k.
'EarthRadius'Mean radius of the Earth6,371,000 m

Examples

collapse all

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);

Introduced in R2011a

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