LR1121
User Manual Rev 1.1
UM.LR1121.W.APP Mar 2023
48 of 130
Semtech
Proprietary & Confidential
www.semtech.com
7. Radio
7.1 Overview
The LR1121 is a half-duplex RF transceiver capable of handling constant envelope modulation schemes such as LoRa,
(G)FSK, and LR-FHSS. The LoRa and (G)FSK modulations are fully compatible with the SX1261/62/68 family for sub-GHz, and
can be configured to be compatible with the SX1280/81 family for 2.4GHz.
The radio system is shown in Figure 7-1: Radio below. It is composed of the frequency synthesizer (also referred as PLL),
three TX paths ( High Power, Low Power and High Frequency), and two RX paths, followed by a high-bandwidth ADC. Both
the ADC and the PLL are tied to the digital subsystem and to the LoRa and (G)FSK modems, and the LR-FHSS modulator.
The PAs are described in a dedicated section, as well as the LoRa and (G)FSK modems, and the LR-FHSS modulation.
Figure 7-1: Radio
The LR1121 frequency synthesizer allows a continuous operation in the 150MHz-2500MHz frequency range. It is shared
between the sub-GHz radio and HF radio, therefore no simultaneous sub-GHz /HF radio operation is possible.
The LR1121 frequency synthesizer is clocked by a 32MHz reference, provided by either a crystal oscillator, or a TCXO. Refer
to Section 6. "Clock Sources" on page 44 for details.
LNA
LF0
PA
HP LF
PA
LP LF
RFO_HP_LF
RFO_LP_LF
RFI_P_LF0
RFI_N_LF0
PA
HF
LNA
HF
Balun
&
Match
RFIO_HF
ADCADC
PLL
VBAT_RF
VR_PA
VREG
DCC_SW
VBAT_DCC
VBAT_RF
DC-DC
LDO
BG/IREF
POR/
BRN
PDS
REGsREGs
HFXOSC
32MHz
CKS
LFXOSC
32kHz
HFRC
32MHz
LFRC
32kHz
XTA
XTB
DIO11/ 32k_P
DIO10/32k_N
VTCXO
DIO0/ BUSY
DIO1
DIO2
DIO3
DIO4
DIO9
DIO8
DIO7
DIO6
DIO5
REG_PA
Digital Baseband
+ DSP
CPU
RAMROM
NVM
IO Control
Digital Front-End
LoRa
modem
(G)FSK
modem
LoRa
modem
(G)FSK
modem
nRESET
150 - 960MHz, RX/TX
1.9 - 2.6GHz, RX/TX
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