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CC1101 loop antenna implementation

PaulSchoenke
Genius 3290 points
Other Parts Discussed in Thread: CC1101

Hello:

I am thinking of using a CC1101 with a loop antenna at  418 MHz. The CC1101 has a differential output but most the reference designs I see have a balun matched to a single ended 50 ohm antenna. Is there an ap-note or other reference that would help in matching the differential output directly to the loop antenna?

Thanks so much!

Paul

  • 0
    TI__Mastermind 31600 points

    Hi Paul,

    Would not recomend to connect a differential antenna directly to CC1101 due to harmonic levels will be too high to pass FCC or ETSI. Even with differential filtering between CC1101 and the differential antenna, still would recommended the standard reference design and a helical antenna approach or flexible / fixed wire antenna.

    Regards,   Richard.

  • 0 in reply to RGW
    Prodigy 95 points

    Hi Richard,

    We are currently designing our product with CC1101 and differential dual band PCB antenna. Our working frequencies are 304MHz and 433.42MHz and expected to work at 1km range. We are now facing issues with harmonics frequencies and unstable RSSI readings. We suspect that this due to the lack of low-pass / band-pass filter on the antenna. Could you suggest what kind of filter suits best this kind of application?

    Thank you

  • 0 in reply to Yohannes64364
    Prodigy 95 points

    Hi Richard,

    Sorry, I forgot to attach our antenna design.

  • 0 in reply to Yohannes64364
    Intellectual 845 points

    Hello,

    We would like to create a watch type product. We are planning to use cc430 for that. From what i have learned from antenna-theory.com, loop antennas are difficult to match but have an advantage compared to a dipole because it doesnt detune easily when near a human body. Any pointers/advice on this?  Thanks

  • 0 in reply to dirt road84483
    TI__Mastermind 31600 points

    Hi,

    Loop antennas are less sensitive to detuning but they also have a smaller bandwidth; they are still detuned. A monopole will have a larger bandwidth and is more sensitive to detuning. Since the bandwidth for the monopole is usually larger, then a shift in frequency can normally be compensated for by the larger bandwidth.

    It is difficult to say which is the best approach but the main issue is to make sure the antenna is well matched in the final application environment. i.e. taking into account detuning parameters such as body effects, casing, grounding and parameters that can load the antenna.

    Regards, Richard

  • 0 in reply to Yohannes64364
    TI__Mastermind 31600 points

    Hi Yohannes64364,

    With this approach I would expect that the harmonics are exceeding the regulatory limits since there is basically no filtering from the radio to the antenna. You need to add a differential filter between the radio and the antenna to solve this.

    Regards,

       Richard