I'm learning about antennas and antenna tuning while constructing LoRaWAN IoT sensor. Normally I find pi-type matching network in devices I have studied, but this one has an extra component. What it is, what is the purpose?

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1 Answer 1


What it is, what is the purpose?

There's a good chance that the antenna it is interfacing with does not have a perfect resistive impedance at the operating frequency. To make a slightly inductive impedance perfectly resistive requires the addition of a parallel or series capacitor of the correct impedance. It's likely that this is what you see on the circuit board.

Looking at the π filter, it has a zero ohm link and only one capacitor fitted hence, in order to make the chip interface purely resistive, it's likely that the same technique is used at that end of the circuit too.

  • \$\begingroup\$ Thanks Andy aka! I'm surprised the coplanar wave part isn't extending all the way to the antenna feed point (the rightmost via) but stops short before trace makes a curve. The copper stops at the same point on both sides of PCB. Would you have an explanation for that? \$\endgroup\$
    – tipo1000
    Jul 4, 2021 at 4:17
  • \$\begingroup\$ @tipo1000 no I don't have an explanation for that but. \$\endgroup\$
    – Andy aka
    Jul 4, 2021 at 9:02

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