wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

Radio Frequency Identification 8-27
FIGURE 8.19 A multibook check out system with an accordion helical antenna camouflaged as a decorative
lighting that points downward to the ferrite sheet hidden under the desk.
irrespective of whether the field exposure is harmful or not. To this end, it is highly recommended that
the high-gain antenna be turned upside down and a sheet of ferrite or some other field-absorbent material
be placed on the spot where the tag is supposed to be read to absorb the excessive electromagnetic
energy (Figure 8.19). In case of a turnstile for access control, the ferrite sheet could be hung on the other
side of the interrogator. In addition, a motion detector could be used to turn on the interrogator, especially
at night.
As the UHF RFID operates at one of the ISM frequencies, its uses in hospitals must be carefully monitored
because an imperfectly shielded interrogator could interfere with the normal operation of sophisticated
medical apparatuses. Due to the unpredictable consequences of electromagnetic interference, a
patient with a pacemaker should never come close to an RFID reader. In other words, a vicinity card is
preferred to an UHF RFID in dispensing medicine in wards because its range is limited to a meter and
the frequency of operation is much lower than those used in medical equipment. The UHF RFID loses
again in the long-range monitoring system for kindergarten children because most parents would not
allow their kids to be exposed to a strong electromagnetic field. In this connection, an active RFID operating
in tailor-made protocols will prevail because the radiation power can be scaled down to milliwatts.
8.34 Era of Artificial Perception
Technically, the RFID is simply another enhancement of the bar code system developed in 1949. The
modification may be minor; its impact on our daily lives is tremendous. Instead of waiting passively for
a tag to present itself one by one for recognition, the UHF RFID differs from other AIDC schemes in its
proactive search for all tags within its range of coverage. Via a tiny tag embedded in every product, or a
small capsule implanted in an animal, or a card carried by a person, an interrogator detects everything
at a distance even when it is blocked by obstacles.
The role reversal is not just new in the AIDC; it is also revolutionary in a computer. Today, a computer
may feel the effects due to various stimulants, such as light, sound, smell, temperature, humidity,
and pressure via appropriate transducers. These inputs could then be used to adjust the ambient
conditions, to respond to the imminent collision, to fine-tune the predetermined path of motion, and
for other passive reactions. However, a computer is not equipped to look for the sources of stimulants
© 2011 by Taylor and Francis Group, LLC