5% of the tag space will be covered with 90% read accuracy. The fourth
reader brings another 4% of the tag space into the 90% read accuracy region and the
covered space becomes saturated as n0 increases. Due to the limitation in candidate
antenna positions in the example, some corners of the portal space will not be covered
even with 18 antennas.
10.4 Conclusions and Extensions
Imperfect read rates constitute a major obstacle to the widespread adoption of RFID
technology. Without human intervention, it is hard to ?¬?x the location and orientation of
a tag during the interrogation process. Hence, multiple reader antennas have been used in
portals, docks, etc., to improve read accuracy and the powering region. Properly locating
these antennas is essential to the success of RFID portal designs. In this chapter, we have
addressed the important but dif?¬?cult problem of determining the location of RFID interrogators
to maximize read accuracy.
50
55
60
65
70
75
80
85
90
0 50 100 150 200 250 300 350 400 450 500
Number of discretized orientations
Coverage percentage (%)
Coverage
percentage for two
reader antennas
placement
Coverage
percentage for three
reader antennas
placement
FIGURE 10.10
Optimal coverage percentage for different numbers of discretized orientations.
FIGURE 10.11
Optimal coverage percentage for different
numbers of reader antennas.
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