Antennas
6.4 SIMATIC RF640A
SIMATIC RF600
288
System Manual, 06/2019, J31069-D0171-U001-A22-7618
6.4.6.3
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/dBic value and a
second dBi/dBic value.
Deviation from maximum antenna gain [dBr]
Read/write range [%]
0
100
-3
70
-6
50
-9
35
-12
25
-15
18
-18
13
Example
As can be seen in Directional radiation patterns in the ETSI frequency band (Page 279), the
maximum antenna gain in the vertical plane is 3.45 dBi (6.45 dBic). In this plane, and with
the polarization axis of the transponder parallel to the axis of symmetry of the antenna, the
antenna gain drops to about 0.5 dBic at +50° or 310°. Therefore the dBr value is -6. The
antenna range is only 50% of the maximum range at + 50° or 310° from the Z axis within the
vertical plane (see values shown in blue in the directional radiation pattern: Characteristic of
the vertical plane of the antenna (Page 279) and the associated representation of the
reference system (Page 278)).
