“Dipole field strength in free space”的意思、由来-开放百科全书

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Dipole field strength in free space

释义

Power density
Numerical values
See also
References and notes

Dipole field strength in free space, in telecommunications, is the electric field strength caused by a half wave dipole under ideal conditions. The actual field strength in terrestrial environments is calculated by empirical formulas based on this field strength.

Power density

Let N be the effective power radiated from an isotropic antenna and p be the power density at a distance d from this source^[1]

Power density is also defined in terms of electrical field strength;

Let E be the electrical field and R be the impedance of the free space

The following relation is obtained by equating the two,

or by rearranging the terms

Numerical values

Impedance of free space is roughly

Since a half wave dipole is used, its gain over an isotropic antenna ( ) should also be taken into consideration,

In this equation SI units are used.

Expressing the same equation in:

kW instead of W in power,

km instead of m in distance and

mV/m instead of V/m in electric field

is equivalent to multiplying the expression on the right by .^[2] In this case,

References and notes

1. ^Reference data for radio Engineers, Howard W.Sams co,Indianapolis, 1956, 27-7
2. ^ K.H.Kaltbeitzer: Site selection, EBU Techhnical Monograph 3104,Bruxelles,1965, p 30

3 : Telecommunication theory|Antennas|Broadcast engineering

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Power density

Numerical values

See also

References and notes