RFM95 Datasheet, PDF (43/121 Pages) List of Unclassifed Manufacturers – Low Power Long Range Transceiver Module

WIRELESS & SENSING
RFM95/96/97/98(W)
PRELIMINARY
DATASHEET
Note No constraint applies to the modulation index of the transmitter, but the frequency deviation must be set between
600 Hz and 200 kHz.
4.2.2.2. OOK Modulation
OOK modulation is applied by switching on and off the power amplifier. Digital control and ramping are available to improve
the transient power response of the OOK transmitter.
4.2.2.3. Modulation Shaping
Modulation shaping can be applied in both OOK and FSK modulation modes, to improve the narrowband response of the
transmitter. Both shaping features are controlled with PaRamp bits in RegPaRamp.
Š In FSK mode, a Gaussian filter with BT = 0.5 or 1 is used to filter the modulation stream, at the input of the sigma-delta
modulator. If the Gaussian filter is enabled when the RFM95/96/97/98(W) is in Continuous mode, DCLK signal on pin
10 (DIO1/DCLK) will trigger an interrupt on the uC each time a new bit has to be transmitted. Please refer to section
5.4.2 for details.
Š When OOK modulation is used, the PA bias voltages are ramped up and down smoothly when the PA is turned on and
off, to reduce spectral splatter.
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 RFM95/96/97/98(W) 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:
0.5 ≤ β
=
2 × F_DEV
----------------------
≤
10
BR
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 13:
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