AS3930 データシートの表示（PDF） - austriamicrosystems AG
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AS3930 Datasheet PDF : 32 Pages
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AS3930
Datasheet - Detailed Description
Table 22. Preamble Requirements in Standard Mode, Scanning Mode and ON/OFF Mode
Bit Rate (bit/s)
Maximum Duration of the Carrier Burst in Standard Maximum Duration of the Carrier Burst in ON/OFF
Mode and Scanning Mode (ms)
Mode (ms)
2520
6.34
10
2340
6.83
10
2184
7.32
10
2048
7.81
10
1926
8.30
10
1820
8.79
10
1724
9.28
10
1638
9.76
10
1560
10.25
10.25
1488
10.75
10.75
1424
11.23
11.23
1364
11.73
11.73
1310
12.21
12.21
1260
12.69
12.69
1212
13.20
13.20
1170
13.67
13.67
1128
14.18
14.18
1092
14.65
14.65
1056
15.15
15.15
1024
15.62
15.62
8.7 False Wake-up Register
The wake-up strategy in the AS3930 is based on 2 steps:
1. Frequency Detection: In this phase, the frequency of the received signal is checked.
2. Pattern Correlation: Here the pattern is demodulated and checked whether it corresponds to the valid one.
If there is a disturber or noise capable to overcome the first step (frequency detection) without producing a valid pattern, then a false wake-up call
happens.Each time this event is recognized a counter is incremented by one and the respective counter value is stored in a memory cell (false
wake-up register). Thus, the microcontroller can periodically look at the false wake-up register, to get a feeling how noisy the surrounding
environment is and can then react accordingly (e.g. reducing the gain of the LNA during frequency detection, set the AS3930 temporarily to
power down etc.), as shown in the Figure 19. The false wake-up counter is a useful tool to quickly adapt the system to any changes in the noise
environment and thus avoid false wake-up events.
Most wake-up receivers have to deal with environments that can rapidly change. By periodically monitoring the number of false wake-up events
it is possible to adapt the system setup to the actual characteristics of the environment and enables a better use of the full flexibility of AS3930.
www.ams.com/LF-Receiver/AS3930
Revision 1.5
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