Data Sheet

LJ1269HC
Rev1.0 Page 26 Web: www.ljelect.com
01b / 20
4
25.0
12.5
00b / 16
4
31.3
15.6
10b / 24
3
41.7
20.8
01b / 20
3
50.0
25.0
00b / 16
3
62.5
31.3
10b / 24
2
83.3
41.7
01b / 20
2
100.0
50.0
00b / 16
2
125.0
62.5
10b / 24
1
166.7
83.3
01b / 20
1
200.0
100.0
00b / 16
1
250.0
125.0
10b / 24
0
333.3
166.7
01b / 20
0
400.0
200.0
00b / 16
0
500.0
250.0
3.4.6. 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 LJ1269HC and its adjustable cutoff frequency fc is controlled in RegRxBw:
Table 15 Available DCC Cutoff Frequencies
DccFreq in RegRxBw
fc in % of RxBw
000
16
001
8
010(default)
4
011
2
100
1
101
0.5
110
0.25
111
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.
3.4.7. Complex Filter - OOK
In OOK mode the LJ1269HC is modified to a low-IF architecture. The IF frequency is automatically set to half the single side
bandwidth of the channel filter (FIF = 0.5 x RxBw). The Local Oscillator is automatically offset by the IF in the OOK receiver. A
complex filter is implemented on the Moduleto attenuate the resulting image frequency by typically 30 dB.
Sub GHz FSK/OOK Transceiver Module DATASHEET