RFM69HCW Datasheet, PDF (27/79 Pages) List of Unclassifed Manufacturers – ISM TRANSCEIVER MODULE

RFM69HCW
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4
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2
01b / 20
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1
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0
25.0
31.3
41.7
50.0
62.5
83.3
100.0
125.0
166.7
200.0
250.0
333.3
400.0
500.0
12.5
15.6
20.8
25.0
31.3
41.7
50.0
62.5
83.3
100.0
125.0
166.7
200.0
250.0
3.4.7. DC Cancellation
DC cancellation is required in zero-IF architecture transceivers to remove any DC offset generated through self-reception.
It is built-in the RFM69HCW and its adjustable cutoff frequency fc is controlled in RegRxBw:
Table 15 Available DCC Cutoff Frequencies
DccFreq
in RegRxBw
000
001
010 (default)
011
100
101
110
111
fc in
% of RxBw
16
8
4
2
1
0.5
0.25
0.125
The default value of DccFreq cutoff frequency is typically 4% of the RxBw (channel filter BW). The cutoff frequency of the
DCC can however be increased to slightly improve the sensitivity, under wider modulation conditions. It is advised to adjust
the DCC setting while monitoring the receiver sensitivity.
3.4.8. Complex Filter - OOK
In OOK mode the RFM69HCW is modified to a low-IF architecture. The IF frequency is automatically set to half the single
side bandwidth of the channel filter (F_IF = 0.5 x RxBw). The Local Oscillator is automatically offset by the IF in the OOK
receiver. A complex filter is implemented on the module to attenuate the resulting image frequency by typically 30 dB.
Note this filter is automatically bypassed when receiving FSK signals (ModulationType = 00 in RegDataModul).
3.4.9. RSSI
The RSSI block evaluates the amount of energy available within the receiver channel bandwidth. Its resolution is 0.5 dB,
and it has a wide dynamic range to accommodate both small and large signal levels that may be present. Its acquisition
time is very short, taking only 2 bit periods. The RSSI sampling must occur during the reception of preamble in FSK, and
constant “1” reception in OOK.
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