Last Updated：2025/11/26
A spherical region of radius λ/2π around a small dipole electromagnetic antenna. This is the distance at which the induction and radiation terms are equal in magnitude. Inside, the induction terms dominate. In radio antenna theory the radiansphere is a convenient definition for the boundary between near-field and far-field regions.
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radiansphere
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Source Word
radiansphere
Noun
A
spherical
region
of
radius
λ/2π
around
a
small
dipole
electromagnetic
antenna.
This
is
the
distance
at
which
the
induction
and
radiation
terms
are
equal
in
magnitude.
Inside,
the
induction
terms
dominate.
In
radio
antenna
theory
the
radiansphere
is
a
convenient
definition
for
the
boundary
between
near-field
and
far-field
regions.
Japanese Meaning
小さなダイポール電磁アンテナを中心とし、半径λ/2πの球状領域を指す用語。近接界（誘導項が支配的な領域）と遠方界（放射項が支配的な領域）との境界としても定義される。
Sense（1）
A
spherical
region
of
radius
λ/2π
around
a
small
dipole
electromagnetic
antenna.
This
is
the
distance
at
which
the
induction
and
radiation
terms
are
equal
in
magnitude.
Inside,
the
induction
terms
dominate.
In
radio
antenna
theory
the
radiansphere
is
a
convenient
definition
for
the
boundary
between
near-field
and
far-field
regions.
（ plural ）
