RFM92 Datasheet, PDF (46/126 Pages) List of Unclassifed Manufacturers – Low Power Long Range Transceiver Module

RFM92W/93W V3.0
The default settings of the OOK demodulator lead to the performance stated in the electrical specification. However, in
applications in which sudden received signal power reduction is possible, the three parameters should be optimized
accordingly.
Optimizing the Floor Threshold
OokFixedThresh determines the sensitivity of the OOK receiver, as it sets the comparison threshold for weak input signals
(i.e. those close to the noise floor). Significant sensitivity improvements can be generated if configured correctly.
Note that the noise floor of the receiver at the demodulator input depends on:
Š The noise figure of the receiver.
Š The gain of the receive chain from antenna to base band.
Š The matching - including SAW filter if any.
Š The bandwidth of the channel filters.
It is therefore important to note that the setting of OokFixedThresh will be application dependant. The following procedure
is recommended to optimize OokFixedThresh.
Set RFM92/3 in OOK Rx mode
Adjust Bit Rate, Channel filter BW
Default OokFixedThresh setting
No input signal
Continuous Mode
Increment
OokFixedThresh
Monitor DIO2/DATA pin
Glitch activity
on DATA ?
Optimization complete
Figure 15. Floor Threshold Optimization
The new floor threshold value found during this test should be used for OOK reception with those receiver settings.
Optimizing OOK Demodulator for Fast Fading Signals
A sudden drop in signal strength can cause the bit error rate to increase. For applications where the expected signal drop
can be estimated, the following OOK demodulator parameters OokPeakThreshStep and OokPeakThreshDec can be
optimized as described below for a given number of threshold decrements per bit. Refer to RegOokPeak to access those
settings.
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