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Minimum antenna impedance

I am using the nrf51822-QFAC-R in an application where the realization of the antenna is very challenging, and I expect to have an antenna |S11|=-1dB, with variations of the impedance depending on the final use case, so I can not design a matching network to match this impedance to the recommended 15+j85Ohm, as each final application would have different impedance. If the impedance seen at ports ANT1 and ANT2 is VERY different from the target one, is there any point in which the PA just stops to work because of the reflection?

From the communications range point of view I am not worried, as the communication has to be done in a range of 10cm aprox, so even if most of the power is lost because of mismatching it will still work, but I am afraid that the PA is not able to work with really bad impedances. Is that the case?

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  • FormerMember
    0 FormerMember

    Almost no matter what you do, you will always get a range of 10 cm. However, the matching network in the reference layout serves multiple purposes: match the chip to 50 and damp harmonics and RX LO while keeping the output power good.

    A lot of reflections caused by bad matching will not create any problems for the PA, but the modulation characteristics may change a little. Other than that, the chip will work normally.

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  • FormerMember
    0 FormerMember

    Almost no matter what you do, you will always get a range of 10 cm. However, the matching network in the reference layout serves multiple purposes: match the chip to 50 and damp harmonics and RX LO while keeping the output power good.

    A lot of reflections caused by bad matching will not create any problems for the PA, but the modulation characteristics may change a little. Other than that, the chip will work normally.

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