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Page 43

RF96/97/98

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DE V

≤ 10

WIRELESS & SENSING

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.

 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 RF96/97/98 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.

 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 RF96/97/98 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:

2 × F

----------------------

0.5

≤ β

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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