SX1262 LoRa Matching Network Design

flux

For exact numeric values, I would not guess. The Semtech material I could access says the 915 MHz network is region-specific, that each region has its own BOM, and that the shown matching values may not be the most up to date; it also notes real designs usually need final tuning for PCB parasitics. That lines up with the rule to use the datasheet/reference design as the source of truth rather than memory
What I can say from the Semtech documentation:
Recommended starting point
  • For 902–928 MHz (US/Canada): start from the PCB_E428V03A SX1262 reference design.
  • For 915–928 MHz (Australia): start from the PCB_E449V01A SX1262 reference design.
Topology Semtech expects at 915 MHz
  • RX balun / impedance transform: 3-element network plus optional shunt part
  • TX match / harmonic filtering: multi-element network from RFO/VR_PA to antenna
  • Semtech gives these 915 MHz impedance targets in the note:
    • TX example load target: 11.7 + j4.8 Ω for max power, or 13.5 + j7.6 Ω for better efficiency
    • RX optimal differential source impedance: 74 + j134 Ω
In your schematic
Your U1 already has the right kind of external network, but the RF parts are still generic and don’t currently show values:
My recommendation
  • Use the Semtech 902–928 MHz SX1262 reference BOM values exactly as the first-spin starting point
  • Then expect to trim with:
    • VNA/S11 on the antenna port
    • conducted TX power / current
    • harmonic measurements
If you want, I can do one of these next:
  1. map your current RF network to the Semtech reference topology node-by-node, or
  2. help you find the exact 902–928 MHz BOM values from the reference schematic/BOM if you upload that PDF.
Map to reference
Upload reference BOM
Review RF layout
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2
3V3
C37
Capacitance
100nF
Voltage
6.3V
3V3
VDD_RF
C36
Capacitance
100nF
Voltage
6.3V
BOOT
S1
R6
Resistance
10KΩ
R17
Resistance
10KΩ
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