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Nrf51422-QFAA with BAL-NRF01D3

Hello, I am developing a board, with nrf51422-qfaa chip. To match the antenna I'm using the BAL-NRF01D3 balun. I currently have problems with antenna not working and I'm trying to "debug" the hardware. I discovered that my antenna trace is shorted to ground. Is it perhaps caused by the balun inner structure? For example, a coil going from antenna trace to ground that is not a shortage for RF frequencies? I'm not sure whether my balun is correctly soldered so I'm trying to narrow the search for the fault.

Below I attached pictures from ST datasheet and it seems that a capacitor is between J1 (antenna) trace and ground, but I'm not sure.

image description image description

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  • FormerMember
    0 FormerMember

    It should work fine to use a balun. But, as you know, it is very small, so one have to be very careful to avoid any short.

    Also, what does your layout look like, is it a copy of the reference layout? It is very important to copy the RF part of the reference layout. It means that there should be a lot of ground, and the distances in your layout should be the same as in our reference layout.

    Do you have a long transmission line towards the antenna? If so, it's important to make sure that the transmission line is a 50 Ohm transmission line (coplanar waveguide).

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  • FormerMember
    0 FormerMember

    It should work fine to use a balun. But, as you know, it is very small, so one have to be very careful to avoid any short.

    Also, what does your layout look like, is it a copy of the reference layout? It is very important to copy the RF part of the reference layout. It means that there should be a lot of ground, and the distances in your layout should be the same as in our reference layout.

    Do you have a long transmission line towards the antenna? If so, it's important to make sure that the transmission line is a 50 Ohm transmission line (coplanar waveguide).

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