Specifications

5.8. IMPROVEMENTS AND FURTHER WORK
to be connected, either in a different orientation or in another location.
This has the potential to decrease system costs (by using only one processor
where two were previously required), improve reliability (by orienting the two
receivers differently in the same location, additional transponder orientations
are accommodated) and improve efficiency (a single charge pulse can be
used for both receivers at a reader station whereas otherwise, two would be
required).
A further proposed optimisation is to remove the expensive MCP602 op-
amp and feed the signal after the tuned filter directly into a PIC 18F4620
processor’s on-board comparator peripheral. Such a system would reduce
the noise introduced by the additional op-amp amplifiers and decrease device
costs.
Overall device performance could be increased by using two inde pendent
high-Q antennae: one for receiving 123.2kHz and another for receiving and
transmitting 134.2kHz. This would reduce received noise and improve receiver
sensitivity while enabling very high transmitter efficiencies. A modification
of this is to use a single antenna which is highly tuned to 134.2kHz. The
receiver would receive the 134.2kHz signal, but not the 123.2kHz signal from
the transponder. Thus, the presence of a signal would indicate a “0” and the
lack of signal for one bit period indicates that “1” was transmitted.
Ultimately, however, Application Spec ific IC (ASIC)-based RFID devices
may prove to be a cheaper alternative to a purely microprocessor-based
reader. The PIC 18F452 used in this reader,or PIC 18F4520 equivalent
replacement, costs approximately ZAR65.00
8
whereas the Texas Instruments
RI-TMS3705ADR is available in unit prices of less than ZAR61.00 for single
items, or ZAR37.00 for purchases of over 100 units
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. One of these ICs would
still require a mic roprocessor controller, however, it will not need the large
volumes of RAM or additional p eripherals that the current design does. A
reader employing a small processor, ASIC RFID device and push-pull output
stage may prove to be a cheaper de sign.
8
Avnett Kopp, September 2006
9
6.43 Euros singly and 3.90 Euros for order over 100. Assuming an exchange rate of
ZAR9.50 to 1 Euro
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