SARA-G3 and SARA-U2 series - System Integration Manual
UBX-13000995 - R26 System description
Page 15 of 217
Memory
V_BCKP (RTC)
V_INT (I/O)
RF
transceiver
Power
Management
Cellular
BaseBand
Processor
ANT
VCC (Supply)
USB
DDC (I
2
C)
SIM card detection
SIM
UART
Power-On
Reset
Digital audio (I
2
S)
GPIO
Antenna detection
3G PA
26 MHz
Duplexer
Filter
Switch
LNA
32 kHz
Figure 5: SARA-U280 modules block diagram
1.2.1 Internal blocks
SARA-G3 and SARA-U2 series modules internally consist of the RF, Baseband and Power Management sections,
described below with more details than are shown in the simplified block diagrams of Figure 1 to Figure 5.
RF section
The RF section is composed of the following main elements:
2G / 3G RF transceiver performing modulation, up-conversion of the baseband I/Q signals, down-conversion
and demodulation of the RF received signals. The RF transceiver includes:
Constant gain direct conversion receiver with integrated LNAs
Highly linear RF quadrature GMSK demodulator
Digital Sigma-Delta transmitter GMSK modulator
Fractional-N Sigma-Delta RF synthesizer
3.8 GHz VCO
Digital controlled crystal oscillator
2G / 3G Power Amplifier, which amplifies the signals modulated by the RF transceiver
RF switch, which connects the antenna input/output pin (ANT) of the module to the suitable RX/TX path
RX diplexer SAW (band pass) filters
26 MHz crystal, connected to the digital controlled crystal oscillator to perform the clock reference in active
mode or connected mode
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