SM1211E915TOPIC Semtech, SM1211E915TOPIC Datasheet - Page 19

• 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

In OOK mode, the phase difference between the I and Q channels is kept constant (independent of the transmitted
data). Thus, the first stage of up-conversion creates a fixed frequency signal at the low IF = Fdev (This explains
why the transmitted OOK spectrum is offset by Fdev).
OOK Modulation is accomplished by switching on and off the PA and PA regulator stages. By convention:
After the interpolation filters, a set of four mixers combines the I and Q signals and converts them into a pair of
complex signals at the second intermediate frequency, equal to 1/8 of the LO frequency, or 1/9 of the RF
frequency. These two new I and Q signals are then combined and up-converted to the final RF frequency by two
quadrature mixers fed by the LO signal. The signal is pre-amplified, and then the transmitter output is driven by a
final power amplifier stage.
In Continuous transmit mode, setting the Bit Rate is useful to determine the frequency of DCLK. As explained in
section 5.3.2, DCLK will trigger an interrupt on the uC each time a new bit has to be transmitted.
Bit rate, frequency deviation and TX interpolation filter settings are a function of the reference oscillator crystal
frequency, F
the correct reference oscillator frequency. Please contact your local Semtech representative for further details.
The frequency deviation, Fdev, of the FSK transmitter is programmed through bits MCParam_Freq_dev:
For correct operation the modulation index ß should be such that:
It should be noted that for communications between a pair of SX1211s, that Fdev should be at least 33 kHz to
ensure a correct operation on the receiver side.
Fdev has no physical meaning in OOK transmit mode. However, as has been shown - due to the DDS baseband
signal generation, the OOK signal is always offset by “-Fdev” (see formulas is section 3.2.8). It is suggested that
Fdev retains its default value of 100 kHz in OOK mode.
Rev 7 – Sept 2
ADVANCED COMMUNICATIONS & SENSING
3.3.2. Bit Rate Setting
3.3.3. Alternative Settings
3.3.4. Fdev Setting in FSK Mode
3.3.5. Fdev Setting in OOK Mode
nd
XTAL
, 2008
. Settings other than those programmable with a 12.8 MHz crystal can be obtained by selection of
Fdev
BR
32
64
*
DATA
DATA
1
*
1
val
Page 19 of 92
2
val
(
*
'
' '
MCParam
' ' 1 '
' ' 0
(
Fdev
F
MCParam
BR
⇒
F
⇒
XTAL
XTAL
PAon
PAoff
2
_
Freq
_
BR
_
)
dev
)
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SX1211