4) for either reader. However, because the unreadable orientations shown
below are mutually exclusive with respect to each other, orientations missed by one reader
antenna are covered by the other; hence the position can actually be read with 100%
accuracy using the two reader antennas in conjunction with each other as shown. In a
different example, there could be a point that can have 80% of its orientations read by one
antenna and 80% of its orientations read by a second antenna, but the union of the two
0.5
0.4
0.3
0.2
0.1
??’0.1
??’0.2
0.2
0.1
0
??’0.1
??’0.2 0
0.05
0.1
0.2
0.3
0.25
0.15
0
FIGURE 10.4
90% read accuracy powering region.
188 RFID Handbook: Applications, Technology, Security, and Privacy
antennas results in 95% of the orientations being readable. In this case, the point would not
be in either antenna??™s readable region when the antennas are considered separately but is
readable when the antennas are considered jointly. Unfortunately, in determining the
coverage area for multiple antennas, Corollary 1 cannot be extended to this case since
there is no direct monotonicity result with multiple readers that can be exploited to de?¬?ne
the powering region.
Consequently, there is no straightforward way to ?¬?nd the boundary surface of the
powering region, which can be disjoint and have some irregular shape.
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