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I am designing a PCB following the RX1276 reference design. There are 6 reference designs presented on their website: https://www.semtech.com/products/wireless-rf/lora-connect/sx1276

Pick any of the 6 designs. There are two caps and an inductor between the SMA and the RF Switch (PE4259). The caps are not mentioned in the BOM at all. And, the inductor value is also missing. In the BOM, the inductor is actually assigned a 0-ohm resistor. I'm confused about these three components. Could someone please help me make a decision about these three components?

I've highlighted these components in the image below.

enter image description here

  • The BOM is included in their ZIP file as an Excell file.
  • I am designing for 915 MHz frequency.
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Those are Pi-networks (called that because the arrangement of the three components resembles the Greek character π ). They allow you to match impedances from the LoRa RF output to the antenna. If the LoRa chip is designed for a 50 ohm load and the antenna is a perfect 50 ohm load at the operating frequency, you could just use a 0 ohm resistor in the inductor position and omit the capacitors. But antennas in the real world are rarely perfect. If you have test equipment you can measure the actual antenna impedance and calculate the necessary components to match it to 50 ohms. (Example of a Pi-network calculator here)

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