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Possible to fine-tune/offset frequency of radio (nrf51822) in code?

davman

Hi,

We're using an off the shelf module with a trace antenna that can't be modified. Measured the module once assembled, and due to surrounding plastic materials, the impedance of the antenna is not 50ohm resulting in the resonance frequency being shifted by ~150MHz.

As this is a fixed offset causing a drop in efficiency, I wonder if it's possible via SoftDevice to compensate to this by offsetting the radio accordingly.

System can run either SD 6.0 or 7.0, Bluetooth LE only.

best david

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  • 0

    Hi Håkon,

    Thanks for reply. The situation in our case is that the module & trace antenna we use doesn't allow any type of tuning (no external Pi-netw).. and hand cutting pcb-traces one-by-one in MP wouldn't make sense :-)

    So, this is to me the problem with many modules, is the fact they are tunes with no plastic in close proximity. And in most use-cases (as in ours) it's hard to fit a module with more than ~1-2mm clearance to plastic.

    What we see is that our antenna efficiency is around -2.8 dB at 2402, and worse higher up -3.52 dB at 2480 MHz.

    My wish was if we in code could slightly shift, or rather compensate the base frequency to get the resonant back where it should be.

    best david

  • 0 in reply to davman

    You cannot change the output impedance of the radio. In order to tune this to your application you'll need to adjust the antenna itself. If you do not have any tuning components, and cutting the antenna is not an option, there is unfortunately not much you can do. Modules are made to be generic, and the antenna is one of the components that will suffer due to the different layout/setup. -2.8 dB is not bad (not really good either), especially if it's measured radiated.

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  • 0 in reply to davman

    You cannot change the output impedance of the radio. In order to tune this to your application you'll need to adjust the antenna itself. If you do not have any tuning components, and cutting the antenna is not an option, there is unfortunately not much you can do. Modules are made to be generic, and the antenna is one of the components that will suffer due to the different layout/setup. -2.8 dB is not bad (not really good either), especially if it's measured radiated.

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