64
3 Physical Theory of RFID System Physical Anti-Collision
R = (cT + d )
−1/2 or M = cT + d
(3.16)
where c = a/η
2 , d = b/η
2 , relevant reading distance M = 1/R
2 .
σ = 0.036/m
2
, P rx = −70 dBm, a = 914.87
Let P tx = 30dBm, G tx = G rx = 8dBi,
R 1
R 2
=
cT 2 +d
cT 1 +d
1/2
T = S − L
R i = (T
2
+ H
2
i )
1/2
, we could get the
relationship between the tag’s reading distance and temperature in static state, shown
in Fig. 3.1.
Realistic test is done in several different temperatures, so the corresponding coefficients and temperature compensation could be obtained. When the corresponding
coefficients
c, d are obtained, the mechanism could be given by
R 1
R 2
=
cT 2 + d
cT 1 + d
1/2
(3.17)
Fig. 3.1 Relationship between the tag’s reading distance and temperature in static state
3 Physical Theory of RFID System Physical Anti-Collision
R = (cT + d )
−1/2 or M = cT + d
(3.16)
where c = a/η
2 , d = b/η
2 , relevant reading distance M = 1/R
2 .
σ = 0.036/m
2
, P rx = −70 dBm, a = 914.87
Let P tx = 30dBm, G tx = G rx = 8dBi,
R 1
R 2
=
cT 2 +d
cT 1 +d
1/2
T = S − L
R i = (T
2
+ H
2
i )
1/2
, we could get the
relationship between the tag’s reading distance and temperature in static state, shown
in Fig. 3.1.
Realistic test is done in several different temperatures, so the corresponding coefficients and temperature compensation could be obtained. When the corresponding
coefficients
c, d are obtained, the mechanism could be given by
R 1
R 2
=
cT 2 + d
cT 1 + d
1/2
(3.17)
Fig. 3.1 Relationship between the tag’s reading distance and temperature in static state