Optimizing Processes with RFID and Auto ID, 2009

2 RFID technology
Interfaces
Fig. 2.2 Block diagram of a reading device
Digital part
Generally, a microcontroller takes over the control of the reading device.
The processing power can differ widely here, varying from an 8bit
microcontroller via digital signal processors (DSPs) or programmable
logic (FPGA) up to a 32-Bit processor with a real-time operating
system. Here it becomes apparent that reading devices frequently
deal with far more complex tasks than merely reading a transponder.
Finally, the application decides what performance capability is required.
Analog part
Considerable parts of the robustness and performance capability of
an RFID reading device are determined by the analog circuitry. The
response signals from transponders are nearly always very weak.
Therefore, a high-performing receiver that can deal with both weak
signals and various interferences is the centerpiece of a good reader.
The transmission signal is also generated in the analog part. At the
same time, it is important to ensure that the transmitter provides a
signal that is as “clean” as possible, i.e. free of phase noise and spurious
emissions. This is important for the performance capability,
avoidance of disturbances, and adherence to legal stipulations. The
transmitter must also be thermally stable and robust: for example,
the removal of the antenna during operation must not cause damage
to the transmitter. The transmitter output can be up to 10 W.
Interfaces
The major task of RFID reading devices is communication. Therefore,
they often have several interfaces (Fig. 2.3):
26
RS-232
Ethernet
Dig. I/O
LED
Digital part Analog part
μC
FPGA
DSP
RAM
FLASH
Transmitter
Receiver