ATA5824-PLQW 80 Atmel, ATA5824-PLQW 80 Datasheet - Page 26

• Manufacturer Part Number: ATA5824-PLQW 80
• Manufacturer: Atmel

Specifications of ATA5824-PLQW 80

• Operating Temperature (min): -40C
• Operating Temperature (max): 105C
• Operating Temperature Classification: Industrial
• Product Depth (mm): 7mm
• Product Height (mm): 0.9mm
• Product Length (mm): 7mm
• Operating Supply Voltage (typ): 5V
• Lead Free Status / Rohs Status: Compliant

26
ATA5823/ATA5824
To prevent that the ATA5823/ATA5824 receives and transmit its RF-signals on the same fre-
quency and at the same time. Since the attacker has then to receive and transmit RF signals at
the same frequency and time it will be much more difficult to built the hardware for this kind of
attack, since its own transmitted output power couples back to its receiver.
This mode works as follows:
Both transceivers transmit FSK with a modulation deviation of half the IF (a frequency deviation
of about ±113 kHz), switches the image rejection in the receive path off and uses the transmit
frequency as local oscillator for the receiver. If both transceivers send FSK-low or both send
FSK-high, the resulting IF is close to zero and is filtered out by the IF-filter. Both receivers
receive than a low-signal by using the ASK demodulator as receiver. If the transceivers send dif-
ferent symbols e.g. FSK-low/FSK-high or FSK-high/FSK-low the resulting IF is close to 226 kHz
and the ASK demodulator receives a high-signal. Since the transceivers are synchronized at the
beginning of the data transfer, they can calculate the transmitted data of the other transceiver
from their own transmitted data and the data received from the ASK demodulator.
To use that mode, the received power from the transmitter side of a transceiver should not cou-
ple with a to high magnitude to its LNA otherwise the receive path will be desensitized.
Therefore, two different antennas for transmit and receive are used with good decoupling (see
Figure 5-1 on page 8
Since defined packets are transmitted in FD-mode and the critical point in the transmission is the
synchronization and not the data transfer, the sensitivity in FD-mode is defined for packets with
8 bytes of useful data (usually the response from a crypto-challenge response transmission) and
for a Packet Error Rate PER of 5%. For the full-duplex mode the data rate is fixed to 5 Kbit/s
The sensitivity of the receiver in full-duplex mode is dependant on the absolute power value and
the phase of the power coupled from the PA to the LNA. Due to the phase dependency, three
values are given in the
sensitivity variation.
Table 8-1.
The IC internal decoupling of the RF
mized for +5dBm is 65 dB on a well designed PCB, hence the coupling is mainly due to the
cross-coupling of the antennas.
Power from RF
RF
IN
–30
–35
–40
–45
–50
/dBm
Typical Full-duplex Sensitivity Dependent on the Parasitic Received Power and
Coupling Phase from the PA 433.92 MHz/Full-duplex Mode/5 Kbit/s PER = 5% at
3V, 25°C
OUT
and
at
Table
Figure 6-1 on page
8-1, the first is the typical and the second and third one shows the
Typical Sensitivity/dBm
IN
from RF
–100
–103
–104
–91
–96
9).
OUT
with a power amplifier load impedance opti-
Sensitivity Variation/dBm
–100.5/–104.5
–101.5/–105.5
–97.5/–101.5
–88.5/–92.5
–93.5/–97.5
4829D–RKE–06/06