sx1231h Semtech Corporation, sx1231h Datasheet - Page 29

• Manufacturer Part Number: sx1231h
• Description: Low Power Integrated Uhf Transceiver With On-chip +20dbm Pa
• Manufacturer: Semtech Corporation

3.4.11. FSK Demodulator
The FSK demodulator of the SX1231H is designed to demodulate FSK, GFSK, MSK and GMSK modulated signals. It is
most efficient when the modulation index of the signal is greater than 0.5 and below 10:
The output of the FSK demodulator can be fed to the Bit Synchronizer (described in section 3.4.13), to provide the
companion processor with a synchronous data stream in Continuous mode.
3.4.12. 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 11:
In peak threshold mode the comparison threshold level is the peak value of the RSSI, reduced by 6dB. 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.
The default settings of the OOK demodulator lead to the performance stated in the electrical specification. However, in
applications in which sudden signal drops are awaited during a reception, the three parameters should be optimized
accordingly.
Rev 1 - Oct 2011
ADVANCED COMMUNICATIONS & SENSING
RSSI
[dBm]
Figure 11. OOK Peak Demodulator Description
Zoom
Zoom
OokPeakThreshDec
Decay in dB as defined in
Period as defined in
OokPeakThreshStep
0.5 β
≤
=
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2 F
----------------------
×
BR
DEV
≤
10
Fixed 6dB difference
‘’Peak -6dB’’ Threshold
‘’Floor’’ threshold defined by
OokFixedThresh
Noise floor of
receiver
SX1231H
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