STS1TX datasheet(39/70 Pages) STMICROELECTRONICS

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DocID025109 Rev 1

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STS1TX

Transmission and reception

For fXO = 26 MHz

With this solution the maximum deviation for the 26 MHz case is limited to about 355 kHz,

but this is still acceptable since the maximum useful deviation is about 125 kHz (MSK @

500 kbps).

In GFSK mode the Gaussian filter BT product can be set to 1 or 0.5 by the field BT_SEL of

the MOD0 register.

In MSK mode, the frequency deviation is automatically set to ¼ of the data rate and the

content of the FDEV register is ignored.

The calculation done within the modem assumes that the digital clock is equal to the

synthesizer reference. Hence, in the 52-MHz case the MSK can actually be configured by

setting the frequency deviation to ¼ of the data rate through the FDEV registers as for

normal 2-FSK. The same is true for GMSK mode, which can be configured by setting the

frequency deviation to ¼ of the data rate through the FDEV registers as for normal GFSK

with Gaussian filter BT equal to 1 or 0.5.

E/M

01234567

793.5

991.8

1190.2

1388.5

1586.9

1785.3

1983.6

2182.0

2380.4

2578.7

2777.1

2975.5

3173.8

3570.6

3967.3

4364.0

4760.7

5157.5

5554.2

5950.9

6347.7

7141.1

7934.6

8728.0

9521.5

10314.9

11108.4

11901.9

12695.3

14282.2

15869.1

17456.1

19043.0

20629.9

22216.8

23803.7

25390.6

28564.5

31738.3

34912.1

38085.9

41259.8

44433.6

47607.4

50781.3

57128.9

63476.6

69824.2

76171.9

82519.5

88867.2

95214.8

101562.5

114257.8

126953.1

139648.4

152343.8

165039.1

177734.4

190429.7

203125.0

228515.6

253906.3

279296.9

304687.5

330078.1

355468.8

380859.4

406250.0

457031.3

507812.5

558593.8

609375.0

660156.3

710937.5

761718.8

E/M