SM1211E915TOPIC Semtech, SM1211E915TOPIC Datasheet - Page 18

• 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 SX1211 is set to transmit mode when MCParam_Chip_mode = 100.
The baseband I and Q signals are digitally generated by a DDS whose digital to analog converters (DAC) followed
by two anti-aliasing low-pass filters transform the digital signal into analog in-phase (I) and quadrature (Q)
components whose frequency is the selected frequency deviation (Fdev).
In FSK mode, the relative phase of I and Q is switched by the input data between -90° and +90° with co ntinuous
phase. The modulation is therefore performed at this initial stage, since the information contained in the phase
difference will be converted into a frequency shift when the I and Q signals are up-converted in the first mixer
stage. This first up-conversion stage is duplicated to enhance image rejection. The FSK convention is such that:
Rev 7 – Sept 2
ADVANCED COMMUNICATIONS & SENSING
RFIO
3.3. Transmitter Description
3.3.1. Architecture Description
nd
, 2008
PA
Amplification
RF
up-conversion
Second
Figure 8: Transmitter Architecture
Q
I
DATA
DATA
Figure 9: I(t), Q(t) Overview
LO1 Tx
IF
First up-conversion
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'
' '
' ' 1 '
' ' 0
⇒
⇒
Q
Q
I
I
Fdev
Frf
1
Frf
LO2 Tx
LO2 Tx
Fdev
Fdev
Interpolation
filters
I(t)
Q(t)
Baseband
DACs
Waveform
generator
DDS
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SX1211
Data
Clock