I
NTEGRATED
C
IRCUITS
D
IVISION
NCD1015-LGA
R00A PRELIMINARY 5
4.2 Communication Signal Interface - Tag to Reader
4.2.1 Frequency
The tag shall be capable of communicating with the reader via an inductive coupling, whereby the power is switched
off and the data are FSK modulated using the frequencies:
• f
0
= 134.2kHz for the Data “Low Bit” Encoding. . . . . (ISO 11785 tolerance)
• f
1
= 124.2kHz for the Data “High Bit” Encoding . . . . (ISO 11785 tolerance)
f
1
represents the frequency for a data bit '1' (t
d1
=16/f
1
) and f
0
for the data bit '0' (t
d0
= 16/f
0
).
The low and high bits have different duration, because each bit takes 16 RF cycles to transmit. The high bit has a
typical duration of ~130Ps, the low bit of ~120Ps. Figure 3 shows the FSK encoding principle used.
Figure 3: FSK Transmission Used During the Read Phase
4.2.2 Transponder Data Rate and Data Coding
The data coding is based on the NRZ method, thus achieving an average data rate of ~8kbit/s based on an equal
distribution of '0' and '1' data bits.
4.3 Communication Signal Interface - Reader to Tag
4.3.1 Modulation
Communication between reader and transponder takes place using ASK modulation of the RF field with a modulation
index of ~100%. The carrier frequency of the RF operating field is f
C
= 134.2 kHz.
4.3.2 Reader Data Rate and Data Coding
The reader to transponder communication uses Pulse Interval Coding (PIC). The reader creates pulses by switching
the carrier on and off as described below. The modulation index of this amplitude modulation is 90% to 100%. The
time between the falling edges of the pulses determines either the value of the data bit, "0" or "1", a Code violation, or
a Stop (EOF) condition. t
1
separates the single intervals. Its duration is t
1
< 40· t
C
.
