SX1239(2010) データシートの表示（PDF） - Semtech Corporation
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SX1239 Datasheet PDF : 73 Pages
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SX1239
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
Table 10 Available RxBw Settings
RxBwMant
(binary/value)
10b / 24
01b / 20
00b / 16
10b / 24
01b / 20
00b / 16
10b / 24
01b / 20
00b / 16
10b / 24
01b / 20
00b / 16
10b / 24
01b / 20
00b / 16
10b / 24
01b / 20
00b / 16
10b / 24
01b / 20
00b / 16
10b / 24
01b / 20
00b / 16
RxBwExp
(decimal)
7
7
7
6
6
6
5
5
5
4
4
4
3
3
3
2
2
2
1
1
1
0
0
0
RxBw (kHz)
FSK
OOK
ModulationType=00 ModulationType=01
2.6
1.3
3.1
1.6
3.9
2.0
5.2
2.6
6.3
3.1
7.8
3.9
10.4
5.2
12.5
6.3
15.6
7.8
20.8
10.4
25.0
12.5
31.3
15.6
41.7
20.8
50.0
25.0
62.5
31.3
83.3
41.7
100.0
50.0
125.0
62.5
166.7
83.3
200.0
100.0
250.0
125.0
333.3
166.7
400.0
200.0
500.0
250.0
3.4.6. DC Cancellation
DC cancellation is required in zero-IF architecture receivers to remove any DC offset generated through self-reception. It is
built-in the SX1239 and its adjustable cutoff frequency fc is controlled in RegRxBw:
fc = ---------4-----×-----R----x---B----w-----------
2π × 2DccFreq + 2
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 SX1239 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 chip to attenuate the resulting image frequency by typically 30 dB.
Note this filter is automatically bypassed when receiving FSK signals (ModulationType = 00 in RegDataModul).
Rev 2 - April 2010
Page 21
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