si4430 Silicon Laboratories, si4430 Datasheet - Page 47

• Manufacturer Part Number: si4430
• Description: Si4430 Ism Transceiver
• Manufacturer: Silicon Laboratories

7. RX Modem Configuration
7.1. Modem Settings for FSK and GFSK
The modem performs channel selection and demodulation in the digital domain. The channel filter bandwidth is
configurable from 620 to 2.6 kHz. The data-rate, modulation index, and bandwidth are set via registers 1C–25. The
modulation index is equal to 2 times the peak deviation divided by the data rate (Rb).
Table 16 gives the modem register settings for various common data-rates. Select the desired data-rate (Rb), and
Deviation (Fd) to determine the proper register settings. For data-rates and modulation types not listed in the table
a calculator tool within WDS can be used.
When Manchester coding is disabled, the required channel filter bandwidth is calculated as BW = 2 x (Fd + 0.25Rb)
where Fd is the frequency deviation and Rb is the data rate. For modulation indices below 1 the required channel
filter bandwidth is calculated as BW = Fd + Rb. The channel filter needs to be increased when the frequency offset
between transmitter and receiver is more than half the channel filter bandwidth. In this case it is recommended to
enable the AFC and choose the IF bandwidth equal to 2 x frequency offset.
kbps
19.2
38.4
57.6
100
100
125
2.4
2.4
4.8
4.8
9.6
9.6
Rb
10
10
20
20
40
40
50
2
Application parameters
19.6
28.8
kHz
300
125
4.8
4.8
4.8
9.6
Fd
36
45
45
40
10
40
20
40
25
50
5
5
mod index
30.00
18.75
5.00
4.00
2.00
1.00
9.38
1.00
8.00
1.00
1.00
4.00
1.02
1.00
2.00
1.00
1.00
1.00
6.00
2.00
Table 16. RX Modem Configurations for FSK and GFSK
BW -3dB
191.5
620.7
335.5
112.1
11.5
11.5
75.2
12.1
95.3
18.9
95.3
18.9
37.7
37.7
95.3
75.2
75.2
75.2
kHz
90
90
RX Modem setting examples for GFSK and FSK
dwn3_bypass
1Ch
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
Preliminary Rev. 0.4
ndec_exp[2:0]
1Ch
3
3
0
3
0
2
0
2
0
1
1
0
0
0
0
0
0
0
0
0
Register values (hex)
filset[3:0]
1Ch
3
3
1
4
4
1
4
1
3
1
1
4
1
1
5
1
3
F
E
8
rxosr[10:0]
20,21h
0D0
0C8
0FA
683
068
341
068
1A1
064
190
068
064
068
064
064
050
045
078
078
060
ncoff[19:0]
21,22,23h
1D7DC
09D49
04EA5
147AE
051EC
147AE
0A3D7
147AE
147AE
08312
013A9
13A93
02752
13A93
13A93
13A93
1999A
15555
11111
11111
Si4430
crgain[10:0]
24,25h
4EE
4EE
4D5
2AD
06B
0A0
005
278
00A
024
521
02B
521
0A6
521
291
668
76E
446
0B8
47