Data Sheet

LJ1269HC
Rev1.0 Page 28 Web: www.ljelect.com
Figure 9. Cordic Extraction
3.4.10. FSK Demodulator
The FSK demodulator of the LJ1269HC 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.
3.4.11. 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:
、
Figure 10. OOK Peak Demodulator Description
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.
Sub GHz FSK/OOK Transceiver Module DATASHEET
0.5≤β=
2×𝐹
𝐷𝐸𝑉
𝐵𝑅
≤10