S2-LP Datasheet, PDF (31/90 Pages) STMicroelectronics – Excellent receiver selectivity and blocking

S2-LP
fxo [MHz]
24
25
26
48
50
52
Table 36: Channel spacing resolution
Channel spacing resolution [Hz]
732.42
762.94
793.45
1464.84
1525.88
1586.91
Block description
5.4
Digital modulator
The S2-LP supports frequency modulation: 2-FSK, 4-FSK, 2-GFSK, 4-GFSK as well
amplitude modulation OOK and ASK. Using register, the user can also program an
unmodulated carrier for lab test and measurement. A special mode, Direct Polar
Modulation, allows building specific modulation scheme controlling directly the amplitude
and the frequency of the carrier synthesized. The register MOD_TYPE is used to select
one of the following modulation scheme.
Table 37: Modulation scheme
MOD_TYPE
Modulation scheme
000b
2-FSK
001b
4-FSK
010b
2-GFSK
011b
4-GFSK
101b
ASK/OOK
110b
Direct Polar (TX)
111b
CW
5.4.1
Frequency modulation
For frequency modulation 2-(G)FSK and 4-(G)FSK the frequency deviation can be tuned in
wide range that depends on 𝑓_{𝑥𝑜} (XTAL frequency) according the following formula:
Equation 7 – Frequency deviation
𝑓_{𝑑𝑒𝑣}
=
𝑓_{𝑋𝑂}
{ 2¹⁹
·
𝑓_{𝑋𝑂}
2¹⁹
·
𝑟𝑜𝑢𝑛𝑑(𝐷
· 𝐹𝐷𝐸𝑉_𝑀
𝐷 · 𝐵
·
𝐵⁄8)
𝑖𝑓𝐹𝐷𝐸𝑉_𝐸
=
0
𝑟𝑜𝑢𝑛𝑑(𝐷
·
(256
+
𝐹𝐷𝐸𝑉_𝑀)
𝐷 · 𝐵
·
2^{(𝐹𝐷𝐸𝑉𝐸−1)}
·
𝐵⁄8)
𝑖𝑓𝐹𝐷𝐸𝑉_𝐸
>
0
Where 𝑓_{𝑥𝑜} is the XTAL oscillation frequency, D is the reference divider and B is the band
selector.
The frequency deviation programmed corresponds to the deviation of the outer
constellation symbols. The deviation of the inner symbols is 1/3 of such programmed
values as reported in where 4 options are available.
DocID029944 Rev 1
31/90