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physconst

Physical constants

Syntax

Const = physconst(Name)

Description

Const = physconst(Name) returns the constant corresponding to the string Name in SI units. Valid values of Name are 'LightSpeed', 'Boltzmann', and 'EarthRadius'.

Input Arguments

Name

String that indicates which physical constant the function returns. The valid strings are not case sensitive.

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

Examples

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Wavelength Corresponding to Known Frequency

Determine the wavelength of an electromagnetic wave whose frequency is 1 GHz.

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

Thermal Noise Power

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

Define 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);
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