ATA5811_06 Datasheet, PDF (13/92 Pages) ATMEL Corporation – UHF ASK/FSK TRANSCEIVER

ATA5811/ATA5812
5.6 Blocking, Selectivity
As can be seen in Figure 5-3 and Figure 5-4, the receiver can receive signals 3 dB higher than
the sensitivity level in presence of very large blockers of –47 dBm/–34 dBm with small frequency
offsets of ±1/ ±10 MHz.
Figure 5-3 shows narrow band blocking and Figure 5-4 wide band blocking characteristics. The
measurements were done with a useful signal of433.92 MHz/FSK/20 Kbit/s/±16 kHz/Manches-
ter with a level of –106 dBm + 3 dB = –103 dBm which is 3 dB above the sensitivity level. The
figures show how much a continuous wave signal can be larger than –103 dBm until the BER is
higher than 10^-3. The measurements were done at the 50Ω input according to Figure 5-1 on
page 10. At 1 MHz, for example, the blocker can be 56 dB higher than –103 dBm which is
–103 dBm + 56 dB = –47 dBm. These values, together with the good intermodulation perfor-
mance, avoid the need for a SAW filter in the key fob application.
Figure 5-3.
Narrow Band 3 dB Blocking Characteristic at 433.92 MHz
70,0
60,0
50,0
40,0
30,0
20,0
10,0
0,0
-10,0
-5,0 -4,0 -3,0 -2,0 -1,0 0,0 1,0 2,0 3,0 4,0 5,0
Distance of Interfering to Receiving Signal [MHz]
Figure 5-4.
Wide Band 3 dB Blocking Characteristic at 433.92 MHz
80,0
70,0
60,0
50,0
40,0
30,0
20,0
10,0
0,0
-10,0
-50,0 -40,0 -30,0 -20,0 -10,0 0,0 10,0 20,0 30,0 40,0 50,0
Distance of Interfering to Receiving Signal [MHz]
13
4689F–RKE–08/06