0
10
20
30
40
50
60
70
80
90
100
Number of reader antennas
1 3 5 7 9 11 13 15 17
Optimal coverage percentage (%)
196 RFID Handbook: Applications, Technology, Security, and Privacy
The orientation and polarization of antennas from both readers and tags have direct
impacts on the power received and the success of an interrogation process; therefore, the
read range parameter, which is de?¬?ned under ideal conditions, is too simplistic to describe
the powering region of RFID interrogators. To fully answer the question of where to
locate the RFID antennas requires the use of an expanded Friis??™ equation and careful
de?¬?nition of the terms read accuracy and powering region.
Although Greene [2] has provided an ef?¬?cient methodology for determining the powering
region of a single reader antenna, merging the powering regions of individual antennas
underestimates the real powering region of a multiple reader antenna con?¬?guration. An
enumeration scheme is developed, where the number of Friis??™ equation evaluations is
CNn
L M, where N is the number of candidate antenna locations, n is the number of
antennas to be installed, L is the number of discretized tag positions, and M is the number
of discretized orientations for each tag position. However, the computational effort
required for this approach can be overwhelming if these parameters are selected for high
resolutions.
Pages:
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388