84
3 Physical Theory of RFID System Physical Anti-Collision
However, little research has been done on the dynamic identification of RFID in
the salt mist environment. In this chapter, a semi-physical experiment chamber for
simulating salt mist environment is designed, which simulates a gradual process from
low to high concentration of salt mist environment in 80% humidity environment.
Then, a RFID dynamic identification platform based on salt mist environment is
designed and built. The system gets the distance between the reader antenna and
the tags in salt mist environment with different concentrations. The variation of
conductivity in different concentrations in salt mist environment impacted the RFID
recognition distance is studied. The theoretical derivation is given.
(1) Fundamental principle
Electromagnetic waves are transmitted from the antenna to the surrounding space to
encounter UHF RFID electronic tags. A part of the electromagnetic energy reaching
the electronic tag is absorbed, and the other part is reflected in different directions
with different strengths. Some of them eventually return to the transmitting antenna,
and the system reads the tag information. The change of NaCl concentration in salt
mist environment will affect the conduction of electromagnetic waves. The change
of humidity will affect the threshold power of electronic tags. We will analyze them
one by one.
In our study, the NaCl solution in the salt mist environment is uniformly isotropic.
In order to form the salt mist environment with different concentrations, we chose
different concentrations of NaCl solutions to be used in the experimental box. The
relationship between conductivity and concentration of NaCl solution under 18°C is
shown in Table 3.6 [32].
The communication between the reader and the tag is established by backscattering electromagnetic waves in the far field. In our study, the salt mist environment in
test chamber is homogeneous isotropic, with dielectric constant is ε, permeability is
μ, and conductivity is σ . According to the general wave equation of electromagnetic
wave propagation [33], when electromagnetic waves enter the salt mist environment
from the air, the electric field in the salt mist environment is:
Table 3.6 Relationship
between conductivity and
concentration of NaCl
solution
Concentration/(mol/L)
Conductivity/(S/m)
0.001
0.011
0.005
0.052
0.010
0.120
0.050
0.479
0.100
0.920
0.500
4.045
1.000
7.430
2.000
12.96
3 Physical Theory of RFID System Physical Anti-Collision
However, little research has been done on the dynamic identification of RFID in
the salt mist environment. In this chapter, a semi-physical experiment chamber for
simulating salt mist environment is designed, which simulates a gradual process from
low to high concentration of salt mist environment in 80% humidity environment.
Then, a RFID dynamic identification platform based on salt mist environment is
designed and built. The system gets the distance between the reader antenna and
the tags in salt mist environment with different concentrations. The variation of
conductivity in different concentrations in salt mist environment impacted the RFID
recognition distance is studied. The theoretical derivation is given.
(1) Fundamental principle
Electromagnetic waves are transmitted from the antenna to the surrounding space to
encounter UHF RFID electronic tags. A part of the electromagnetic energy reaching
the electronic tag is absorbed, and the other part is reflected in different directions
with different strengths. Some of them eventually return to the transmitting antenna,
and the system reads the tag information. The change of NaCl concentration in salt
mist environment will affect the conduction of electromagnetic waves. The change
of humidity will affect the threshold power of electronic tags. We will analyze them
one by one.
In our study, the NaCl solution in the salt mist environment is uniformly isotropic.
In order to form the salt mist environment with different concentrations, we chose
different concentrations of NaCl solutions to be used in the experimental box. The
relationship between conductivity and concentration of NaCl solution under 18°C is
shown in Table 3.6 [32].
The communication between the reader and the tag is established by backscattering electromagnetic waves in the far field. In our study, the salt mist environment in
test chamber is homogeneous isotropic, with dielectric constant is ε, permeability is
μ, and conductivity is σ . According to the general wave equation of electromagnetic
wave propagation [33], when electromagnetic waves enter the salt mist environment
from the air, the electric field in the salt mist environment is:
Table 3.6 Relationship
between conductivity and
concentration of NaCl
solution
Concentration/(mol/L)
Conductivity/(S/m)
0.001
0.011
0.005
0.052
0.010
0.120
0.050
0.479
0.100
0.920
0.500
4.045
1.000
7.430
2.000
12.96