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CC1101: matching short antenna for 868MHz.

Andrew Buckin
Prodigy 10 points
Part Number: CC1101

Tool/software:

Hello everyone,

  • I am working with CC1101RGPR at 868 MHz.

  • My antenna is very small, and the VNA measurement shows impedance ≈ 6.7 – j10.7 Ω.

I have a few questions regarding the antenna matching:

  1. What would be the recommended approach to match such an antenna?

  2. I was planning to use 0896BM15A0001001E (which, as I understand, already provides a 50 Ω output). After that, I wanted to add a simple LC matching network (L in parallel, C in series).

  3. However, I noticed that in the reference design for 0896BM15A0001001E, there is already a series L and a shunt C to achieve 50 Ω at the output.

This is where I got confused — should I rely only on the network inside 0896BM15A0001001E, or do I still need an additional external LC network for proper matching to my antenna impedance?

Any guidance or recommendations would be greatly appreciated!

Thank you.

  • 0
    TI__Genius 17995 points

    Hi,

    1.

    The following App Notes were written with this in mind:

    2.

    We'd recommend adding the footprint for a Pi-network (placed as close to the antenna as possible).

    3.

    The additional LC filter in the reference design looks to be for harmonic attenuation, not antenna impedance matching. So, you need this LC filter regardless of antenna matching, i.e. the Pi-network would be placed after this LC filter.

    It is likely possible to achieve the filtering and impedance matching with the Pi-filter alone but that would require additional effort and probably simulating the PCB, etc. If you haven't got experience with that process, I'd recommend keeping the LC filter (close to the IPC as in the reference design), plus the DC blocking capacitor, and then adding a Pi-network (close to the antenna).

    Regards,

    Zack