Data Sheet

LJ1269HC
Rev1.0 Page 29 Web: www.ljelect.com
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.
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:
 The noise figure of the receiver.
 The gain of the receive chain from antenna to base band.
 The matching - including SAW filter if any.
 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.
Figure 11. 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.
Alternative OOK Demodulator Threshold Modes
In addition to the Peak OOK threshold mode, the user can alternatively select two other types of threshold detectors:
 Fixed Threshold: The value is selected through OokFixedThresh
 Average Threshold: Data supplied by the RSSI block is averaged, and this operation mode should only be used
with DC-free encoded data.
Sub GHz FSK/OOK Transceiver Module DATASHEET