Semtech LR1121 - Impedance Matching Networks; Multi-Band Operation; Table 9-1: Optimized Settings for LP PA with the same Matching Network; Table 9-2: Optimized Settings for HP PA with the same Matching Network

LR1121
User Manual Rev 1.1
UM.LR1121.W.APP Mar 2023
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9.4 Impedance Matching Networks
The high power PA and low power PAs are available on the RFO_HP_LF and RFO_LP_LF pins respectively. They are
connected to the antenna through a dedicated impedance matching network, which aims at presenting the optimized
load at the output pins when loaded with 50Ohms at the antenna level.
The High Frequency PA is available on the RFIO-HF pin. It is internally matched at 50Ohms, reducing the need of external
components for HF operation. Some components present on the RFIO_HF pin in the Semtech reference design are aimed
at providing filtering to comply with the RF regulations.
9.4.1 Multi-Band Operation
It is possible to implement a multi-band configuration using a single impedance matching network, allowing the same set
of SMD components to cover multiple sub-GHz ISM bands. Table 9-1, Table 9-2 and Table 9-3 show the optimal settings for
the PA when using the Semtech matching network obtained on Semtech' s reference design. The user can fine-tune the
PaDutyCycle and PaHpSel according to their requirements of matching network, efficiency, output power, and harmonic
emission. Please note that the effect of PaDutyCycle and PaHpSel on the efficiency, output power, and harmonic emission
are PCB-design dependent, therefore the PA settings shown in must be optimized on the user's application.
The matching network implementation proposed by Semtech is optimized for +22dBm and +15dBm for the higher ISM
bands, i.e. a 868-928MHz operation.
Table 9-1: Optimized Settings for LP PA with the Same Matching Network
Target Power TxPower PaSel RegPASupply PaDutyCycle PaHPSel
+15dBm 14 0 0 7 -
+14dBm 14 0 0 4 -
+10dBm 14 0 0 0 -
Table 9-2: Optimized Settings for HP PA with the Same Matching Network
Target Power TxPower PaSel RegPASupply PaDutyCycle PaHPSel
+22dBm 22 1 1 4 7
+20dBm 22 1 1 3 7
+17dBm 22 1 1 2 4
+14dBm 22 1 1 1 3
Table 9-3: Optimized Settings for HF PA with the Same Matching Network
Target Power TxPower PaSel RegPASupply PaDutyCycle PaHPSel
+13dBm 13 N/A 0 0 0
+12dBm 13 N/A 0 1 0