Balluff BIS U Basishandbuch Seite 38

BIS U Basic Manual
3
Basic Physical Information
3.1 Physics of the
Transmitting
Antenna
8
The UHF antenna is an open oscillating circuit with electric fields that extend into the surrounding
environment. The simplest form of UHF antenna is an electric dipole.
However, field displacement occurs in the vicinity of the antenna due to the high excitation
frequency. The energy stored in the field moves away from the antenna at nearly the speed of
light.
Figure 2: Schematic diagram of the displacement process
The energy propagates over an ever-increasing area as it moves away from the antenna and, as
a result, the field intensity decreases reciprocally in relation to the distance.
This process of attenuation is also known as "free space loss".