Datasheet

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SX1272/73
WIRELESS, SENSING & TIMING DATASHEET
Rev. 2 - July 2014
©2014 Semtech Corporation
Note The transmitter must be restarted if the ModulationShaping setting is changed in order to recalibrate the built-in filter.
4.2.3. FSK/OOK Reception
4.2.3.1. FSK Demodulator
The FSK demodulator of the SX1272/73 is designed to demodulate FSK, GFSK, MSK and GMSK modulated signals. It is
most efficient when the modulation index (
β) of the signal is greater than 0.5 and below 10:
The output of the FSK demodulator can be fed to the Bit Synchronizer to provide the companion processor with a
synchronous data stream in Continuous mode.
4.2.3.2. OOK Demodulator
The OOK demodulator performs a comparison of the RSSI output and a threshold value. Three different threshold modes
are available, configured through bits OokThreshType in RegOokPeak.
The recommended mode of operation is the “Peak” threshold mode, illustrated in Figure 15:
Figure 15. OOK Peak Demodulator Description
In peak threshold mode the comparison threshold level is the peak value of the RSSI reduced by 6 dB. In the absence of
an input signal, or during the reception of a logical ‘0’, the acquired peak value is decremented by one OokPeakThreshStep
every OokPeakThreshDec period.
When the RSSI output is null for a long time (for instance after a long string of “0” received or if no transmitter is present)
the peak threshold level will continue falling until it reaches the “Floor Threshold” programmed in OokFixedThresh.
0.5 β≤
2 F
DEV
×
BR
----------------------
10≤=
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Period as defined in
OokPeakThreshDec
Decay in dB as defined in
OokPeakThreshStep
Fixed 6dB difference
RSSI
[dBm]
Noise floor of
receiver
‘’Floor’’ threshold defined by
OokFixedThresh
Time
‘’Peak -6dB’’ Threshold
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