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3 Physical Theory of RFID System Physical Anti-Collision
3.1 Thermodynamic Analysis of Physical
Anti-Collision—Research on the Effect of Temperature
on Tag Performance
The study of temperature on the antenna has been reported. In [3], Kabacik presented
a thorough study into the performance of microstrip patch antennas that were exposed
to large temperature variations and pointed out that the electrical characteristics of
microstrip antennas were considerably influenced by temperature. Yadavused used
HFSS to study the effect of temperature on microstrip antenna and the results showed
that the bandwidth of antenna remained unchanged and the impedance increased
with the increase of temperature [4]. Cheng designed a temperature sensor due to the
antenna’s sensitization to temperature and found that the resonant frequency of the
antenna decreased with the increase of temperature [5]. Babu found that high temperatures can cause degradation of the antenna’s materials and it would not function well
if the ground plane began to fall apart [6].
However, the above researches are relevant to the effect of temperature on antennas
of chip and IC in the ideal case. Goodrum discovered that low temperature could lead
to difficulty in detecting active tags with a short-read range. When the temperature
was as low as –10 °C, RSSI readings were much lower than tags of 22 °C and represented poor RFID performance [7]. Merilampi analyzed the effects of temperature on
printed passive UHF RFID tags on a paper substrate and found that the temperature
had a severe effect on the tag performance [8]. But the above experiments are about
the static tests on the antenna in a closed space with little reference to the dynamic
tests.
The main theme of the section is to study the influence of temperature on the RFID
tag’s dynamical reading performance. We derived an identical equation on reading
distance and working frequency of RFID tag, and then converted it to the one on
reading distance and environment temperature. Subsequently, the experimentation
system, including the temperature control system and experimentation platform, was
designed. According to the result of measurement, a fitting model between temperature and reading distance was established and the threshold temperature of UHF
tags was obtained. Finally, a temperature compensating mechanism was derived to
get the reading distance of a tag at the same reference temperature. The numerical and actual experiments showed that this method was applied to the dynamic
measurement of RFID tag’s reading performance, which had the advantages of high
measuring accuracy, stable performance, and quick response speed.
3.1.1 Fundamental Principles
(1) Theory of heat transfer
The environment temperature affects the performance of tags via heat conduction,
heat convection, and heat radiation.
3 Physical Theory of RFID System Physical Anti-Collision
3.1 Thermodynamic Analysis of Physical
Anti-Collision—Research on the Effect of Temperature
on Tag Performance
The study of temperature on the antenna has been reported. In [3], Kabacik presented
a thorough study into the performance of microstrip patch antennas that were exposed
to large temperature variations and pointed out that the electrical characteristics of
microstrip antennas were considerably influenced by temperature. Yadavused used
HFSS to study the effect of temperature on microstrip antenna and the results showed
that the bandwidth of antenna remained unchanged and the impedance increased
with the increase of temperature [4]. Cheng designed a temperature sensor due to the
antenna’s sensitization to temperature and found that the resonant frequency of the
antenna decreased with the increase of temperature [5]. Babu found that high temperatures can cause degradation of the antenna’s materials and it would not function well
if the ground plane began to fall apart [6].
However, the above researches are relevant to the effect of temperature on antennas
of chip and IC in the ideal case. Goodrum discovered that low temperature could lead
to difficulty in detecting active tags with a short-read range. When the temperature
was as low as –10 °C, RSSI readings were much lower than tags of 22 °C and represented poor RFID performance [7]. Merilampi analyzed the effects of temperature on
printed passive UHF RFID tags on a paper substrate and found that the temperature
had a severe effect on the tag performance [8]. But the above experiments are about
the static tests on the antenna in a closed space with little reference to the dynamic
tests.
The main theme of the section is to study the influence of temperature on the RFID
tag’s dynamical reading performance. We derived an identical equation on reading
distance and working frequency of RFID tag, and then converted it to the one on
reading distance and environment temperature. Subsequently, the experimentation
system, including the temperature control system and experimentation platform, was
designed. According to the result of measurement, a fitting model between temperature and reading distance was established and the threshold temperature of UHF
tags was obtained. Finally, a temperature compensating mechanism was derived to
get the reading distance of a tag at the same reference temperature. The numerical and actual experiments showed that this method was applied to the dynamic
measurement of RFID tag’s reading performance, which had the advantages of high
measuring accuracy, stable performance, and quick response speed.
3.1.1 Fundamental Principles
(1) Theory of heat transfer
The environment temperature affects the performance of tags via heat conduction,
heat convection, and heat radiation.