Digital Signal Processing Reference
In-Depth Information
The required bandwidth is derived from the bandwidth of the modulation sidebands of
the reader and the load modulation products (if no other procedure is used). As a rule
of thumb, the following can be taken as the bandwidth of an ASK modulated system.
B
ยท
T
=
1
(
11
.
10
)
where
T
is the turn-on-time of the carrier signal, where modulation is used.
For many systems, the optimal Q factor is 10-30. However, it is impossible to
generalise here because, as already mentioned, the Q factor depends upon the required
bandwidth and thus upon the modulation procedure used (e.g. coding, modulation,
subcarrier frequency).
11.5
Reader Designs
Different types and designs of readers are available for different applications. Readers
can be generally classified into OEM readers, readers for industrial or portable use and
numerous special designs.
11.5.1
OEM readers
OEM readers are available for integration into customers' own data capture systems,
BDE terminals, access control systems, till systems, robots, etc. OEM readers are
supplied in a shielded tin housing or as an unhoused board. Electrical connections are
in the form of soldered, plug and socket or screw-on terminals. See Figure 11.23.
Figure 11.23
Example of an OEM reader for use in terminals or robots (photo:
Long-Range/High-Speed Reader LHRI, reproduced by permission of SCEMTEC Transponder
Technology GmbH, Reichshof-Wehnrath)
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