OBID
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Antenna Manual
ID RW24
FEIG ELECTRONIC GmbH
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h80391-1e-ID.doc
The optimal shield size for transponders of the ID DTK.B-A –type (transponder card) is approx. 50
cm x 70 cm. In this case, the gate width should not exceed 1m. Generally, the recognition rate in-
creases if the gate width is reduced.
The inductance of a gate antenna in Helmholtz arrangement is slightly higher than the sum of all
single inductances of the two single antennas.
4.2. Gate antenna in Anti-Helmholtz arrangement
Figure 4.2-1.b shows the field distribution of a gate antenna in Anti-Helmholtz arrangement, as well
as the transponder’s predominant direction for this antenna.
a)
b)
Transponder
Figure 4.2-1
This gate type as well is used mainly for personal identification. The predominant direction of a
transponder for safe recognition is vertical to the shield surface (Figure 4.2-1.b). If this marginal con-
dition is also kept for an object identification devvice, then this arrangement is also suitable for such
a system.
In general, this gate type has a so-called dead range, situated in the middle between the two anten-
nas. Irrespective of the transponder alignment, communication with the transponder is impossible in
this range.
For the dimensions of such a gate, the same conditions apply as for a gate in Helmholtz arrange-
ment. The optimal shield size for transponders of the ID DTK.B-A –type (transponder card) is 50 cm x
70 cm and the gate width should not exceed 1m.
The inductance of a gate antenna in Anti-Helmholtz arrangement is slightly smaller than the sum of
all inductances of the two single antennas.
