Digital Signal Processing Reference
In-Depth Information
10
The Architecture
of Electronic Data Carriers
Before we describe the functionality of the data carriers used in RFID systems we must
first differentiate between two fundamental operating principles: there are
electronic
data carriers
based upon integrated circuits (
microchips
) and data carriers that exploit
physical effects for data storage. Both 1-bit transponders and surface wave components
belong to the latter category.
Electronic data carriers are further subdivided into data carriers with a pure memory
function and those that incorporate a programmable microprocessor (Figure 10.1).
This chapter deals exclusively with the functionality of electronic data carriers. The
simple functionality of physical data carriers has already been described in Chapter 3.
10.1 Transponder with Memory Function
Transponders with a memory function range from the simple
read-only transponder
to
the
high end transponder
with intelligent cryptological functions (Figure 10.2).
Transponders with a memory function contain RAM, ROM, EEPROM or FRAM
and an
HF interface
to provide the
power supply
and permit communication with the
reader. The main distinguishing characteristic of this family of transponders is the
realisation of address and security logic on the chip using a
state machine
.
10.1.1 HF interface
The HF interface forms the interface between the analogue, high frequency trans-
mission channel from the reader to the transponder and the digital circuitry of the
transponder. The HF interface therefore performs the functions of a classical modem
(modulator-demodulator) used for analogue data transmission via telephone lines.
The modulated HF signal from the reader is reconstructed in the HF interface by
demodulation
to create a digital serial data stream for reprocessing in the address and
security logic. A clock-pulse generation circuit generates the system clock for the data
carrier from the carrier frequency of the HF field.
Search WWH ::
Custom Search