Figure 7.8 gives an approximation on the reduction of output power. In the far ?¬?eld
region, using the Friis equation, the power received is the inverse function of the square of
Channel
Frequency
1 2 3 4 5 6 7 8 9 10
FIGURE 7.7
Channeling of the allocated frequency spectrum. (From Leong, K.S.,
M.L. Ng, and P.H. Cole. 2006a. Synchronization of RFID readers for
dense RFID reader environments. International Symposium on Applications
and the Internet. SAINT, Phoenix, Arizona, USA, # 2006 by
IEEE. With permission; Leong, K.S., M.L. Ng, A. Grasso, and P.H.
Cole. 2006d. J. Commun., 1, 9,#2006 by IEEE. With permission.)
Estimation of radiated power
Distance (m) Max = 10 m
Max = 5 m
Radiated power (W ERP)
0
0
0.5
1
1.5
2
2 4 6 8 10
FIGURE 7.8
Estimation of required radiated power
given that maximum read range corresponds
to maximum radiated power.
(From Leong, K.S., M.L. Ng, and P.H.
Cole. 2006a. Synchronization of RFID
readers for dense RFID reader environments.
International Symposium on Applications
and the Internet. SAINT, Phoenix,
Arizona, USA,#2006 by IEEE. With permission;
Leong, K.S., M.L. Ng, A. Grasso,
and P.H. Cole. 2006d. J. Commun., 1, 9,
# 2006 by IEEE. With permission.)
RFID Reader Synchronization 133
distance (r2). If the maximum read range corresponding to maximum radiated power
(2 W ERP) of an RFID reader is known, we can compute the required radiated power for a
shorter read range.
Pages:
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269