Siemens SIMATIC RF600 System Manual page 162

Antennas
6.2 Guidelines for selecting RFID UHF antennas
Beam width
Definition
A further description of the directional characteristic is the beam width. The beam width is
the beam angle at which half the power (-3 dB) is radiated referred to the maximum power.
The antenna gain is directly related to the beam width. The higher the antenna gain, the
smaller the beam angle.
Coupling in ETSI
In ETSI EN 302 308 (release version V1.1.2 2006-07), the radiated power is coupled to the
beam width, i.e.
● Radiated power 500-2000 mW ERP: beam width ≤ 70 degrees
● Radiated power < 500 mW ERP: beam width ≤ 90 degrees
The beam width requirement applies to both the horizontal and vertical planes. The FCC
directives do not envisage coupling with the beam width.
The following graphics show examples of the directional characteristic of an antenna in polar
and linear representations for which both the horizontal and vertical planes must be
considered.
Directional radiation pattern in polar representation
① Beam width
② Spurious lobe
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System Manual, 10/2009, J31069-D0171-U001-A8-7618
SIMATIC RF600