RFID tags are powered in a variety of
ways:
·
Passive. Passive tags are pure passive
devices that are powered by the incoming radio signal, and require no internal
power source. Most passive tags signal by backscattering the carrier wave and
modulating it to transmit data.
·
Active and semi-passive (also known as battery-assisted
or semi-active). Active and semi-passive tags require a power source, usually a
small battery.
·
Beacon. Beacon tags also require a power source. They transmit
autonomously in a blink pattern and do not respond to interrogation.
Communications from active tags to
readers are typically much more reliable (generating fewer errors) than those
from passive tags and are much more robust in complex RF environments since
they can transmit at much higher power levels.
An excellent application of
RFID technology is in the field of contactless RFID smart cards, which are used
for electronic payment in Metro systems. These money cards employ a passive
RFID tag using Manchester coding at 212 kbps in the 13.56 MHz range. A
proximity of 10 centimeters or less is required for communication.
In order to test RFID readers,
signals need to be generated by and transmitted to the tag, whose response is
received and interpreted by the RFID reader. An arbitrary waveform generator
serves as an ideal signal source, simulating the signals transmitted by the
RFID reader.
In order to test the RFID reader, the
waveform generator must be able to generate a 13.56MHz carrier wave together
with a series of binary (0/1) codes that can be combined in any sequence. The
waveform is output for at least 16ms, and the ASK modulation index must have a
range of at least 5%-40%. An example of the waveform is shown in below:
Figure 1: Required
Waveform for RFID Reader Testing
Solution
Tabor Electronics’ Wonder Wave family of ArbitraryWaveform Generators (AWGs) offers an outstanding solution for the testing of
RFID readers and tags. Wonder Wave is easily programmed to generate the carrier wave
and the data specified in the above example. First, the carrier wave and the
data are stored in memory. A sequence is then programmed with the required
data. Background noise and frequency variations can then be applied to test the
reliability of the unit. Wonder Wave’s powerful sequence generator provides outstanding
support for highly complex applications, offering storage of 10,000 repeatable
waveform segments, with up to 4 million memory points. Wonder Wave is supplied with ArbConnection – Tabor’s
comprehensive software tool that controls AWG operation, and supports the
creation of unique, arbitrary waveforms using its powerful Waveform Composer.
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