Siemens SIMATIC RF642A Operating Instructions Manual page 31

Interpretation of directional radiation patterns
The following overview table will help you with the interpretation of directional radiation patterns.
The table shows which dBi values correspond to which read/write ranges (in %): You can read the radiated power
depending on the reference angle from the directional radiation patterns, and thus obtain information on the read/write range
with this reference angle with regard to a transponder.
The dBr values correspond to the difference between the maximum dBi value and a second dBi value.
Deviation from maximum antenna gain [dBr]
0
-3
-6
-9
-12
-15
-18
Example
As can be seen in Directional radiation pattern in the ETSI frequency band (Page 11), the maximum antenna gain in the
horizontal plane is 6 dBi. In this plane and with the parallel polarization axis at +70° or 300°, the antenna gain dropped to
about 0 dBi. Therefore the dBr value is 6. The antenna range is only 70° of the maximum range at + 50° or +300° from the Z
axis within the horizontal plane (see values shown in red in the directional radiation pattern: Characteristic of the vertical
plane of the antenna and the associated representation of the reference system).
14
Read/write range [%]
100
70
50
35
25
18
13
SIMATIC RF642A
J31069-D0226-U001-A2-7618, 12/2010