2. RFID technology
With the use of RFID technology and electromagnetic waves,
users can send and receive data with no contacts occurring
between interrogators and tags. RFID tags can hold more
information than data carrier systems such as bar code
system. Savi Technology has developed sensor-based security
seals called SensorTag ST-646 for securing ocean shipping
containers. This tag can detect both tampering and potential
theft, as well as spoilage or damage of goods. The information
is collected in real time (Chao, 2007).
There are four types of tags in industry that are known as:
1 passive tags;
2 active tags;
3 semi-passive tags; and
4 semi-active tags.
Passive tags get their energy from a remote RFID reader.
An active tag uses a battery for both the chip and the
transmission of data on the antenna. Semi-passive tags use a
small onboard battery to power the chip. Semi-active tags use
the battery for powering the antenna but the chip relies on
the RF energy from the reader (Potter, 2005). The life of active
tags are limited while of passive tags are unlimited. Active tags
are heavier than the passive tags and more costly as well.
RFID systems work at a number of different frequencies
including 125 KHz, 13.56 MHz, 2.45 GHz, and 5.8GHz and
for ultra-high frequency (UHF) 860-950 MHz. Lowfrequency
tags work along 120-140KHz frequencies while
high-frequency tags work along the 13.56MHz RFs. UHF
tags work along the 850-900 MHz. Low-frequency tags are
less expensive and use less power compared to other kinds of
tags. High- and ultra-high tags have better ranges and transfer
data faster (Table I).
The RFID reader acts as a transmitter/receiver. The reader
transmits an electromagnetic field that “wakes up” the tag and