MRF89XAM8A-I Datasheet, PDF (67/140 Pages) Microchip Technology – Ultra Low-Power, Integrated ISM Band Sub-GHz Transceiver

MRF89XA
3.4.10.1 Optimizing the Floor Threshold
The FTOVAL<7:0> bits (FLTHREG<7:0>) determine
the sensitivity of the OOK receiver, as it sets the com-
parison threshold for weak input signals (that is, those
close to the noise floor). Significant sensitivity
improvements can be generated if configured correctly.
The noise floor of the receiver at the demodulator input
depends on the following conditions:
• The noise figure of the receiver
• The gain of the receive chain from antenna to
base band
• The matching, including SAW filter
• The bandwidth of the channel filters
The setting of the FTOVAL<7:0> bits are application-
dependant. The procedure shown in the flow chart in
Figure 3-12 is recommended to optimize the
FTOVAL<7:0> bits.
The new floor threshold value found during this test
should be the value used for OOK reception with those
receiver settings.
Note that if the output signal on DATA is a logic ‘1’, the
value due to the FTOVAL<7:0> bits is below the noise
floor of the receiver chain. Conversely, if the output sig-
nal on DATA is a logic ‘1’, the value due to the
FTOVAL<7:0> bits is several dB above the noise floor.
FIGURE 3-12:
FLOOR THRESHOLD OPTIMIZATION
Set MRF89XA in OOK RX mode
Adjust Bit Rate, Channel filter BW
Default OOKTHSV<2:0> setting
No input signal
Continuous mode
Increment
FTOVAL<7:0>
Yes
Monitor DATA pin (pin 20)
Glitch activity
on DATA ?
No
Optimization complete
© 2010–2011 Microchip Technology Inc.
Preliminary
DS70622C-page 67