SM1211E915TOPIC Semtech, SM1211E915TOPIC Datasheet - Page 28

• Manufacturer Part Number: SM1211E915TOPIC
• Description: KIT PICTAIL EXT FOR SX1211
• Manufacturer: Semtech
• Type: Transceiver, UHFr

Specifications of SM1211E915TOPIC

• Frequency: 915MHz
• For Use With/related Products: SX1211
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The effect of the Fdev setting is different between FSK and OOK modes:
In FSK mode the Fdev setting, as configured by MCParam_Freq_Dev, sets sampling frequencies on the receiver.
The user should make it consistent with the frequency deviation of the FSK signal that is received.
The frequency deviation Fdev, as described above, sets the sampling rate of the RSSI block. It is therefore
necessary to set Fdev to the recommended low-IF frequency, IF2, of 100 kHz:
The FSK demodulator provides data polarity information, based on the relative phase of the input I and Q signals at
the baseband. Its outputs can be fed to the Bit Synchronizer to recover the timing information. The user can also
use the raw, unsynchronized, output of the FSK demodulator in Continuous mode.
The FSK demodulator of the SX1211 operates most effectively for FSK signals with a modulation index greater
than or equal to two:
The OOK demodulator performs a comparison of the RSSI output and a threshold value. Three different threshold
modes are available, programmed through the RXParam_OOK_thresh_type register.
The recommended mode of operation is the “Peak” threshold mode, illustrated below in Figure 22:
Rev 7 – Sept 2
ADVANCED COMMUNICATIONS & SENSING
3.4.8. Fdev Setting in Receive Mode
3.4.9. FSK Demodulator
3.4.10. OOK Demodulator
nd
, 2008
RXParam_RSSI_val(7:0)
IRQParam_RSSI_irq
3.4.8.1. FSK Rx Mode
3.4.8.2. OOK Rx Mode
24 26 27 30 25 20 20 20 18 22
Fdev
MCParam
Figure 21: RSSI IRQ Timings
IF
2
_
Freq
Page 28 of 92
100
2
*
BR
Fdev
kHz
_
dev
Clear interrupt
"
2
00000011
"
33
20 22 34
33
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