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CC1352R: Most efficient PCB antenna for 915MHz

Bruno Lau da Costa
Intellectual 610 points
Part Number: CC1352R
Other Parts Discussed in Thread: CC-ANTENNA-DK2, CC1310, LAUNCHXL-CC1310

Hi,

I'm searching for the best PCB antenna at 915MHz with respect to efficiency (no big concern about size).

I decided to look in CC-Antenna DK and DK2 documents, and I found out that the most efficient antenna at 915MHz is DK1 #10 (DN606), with an efficiency of 63.4%. 

This surprised me, since AN038 states that 

"If PCB board area is sufficient to position the Meandering Monopole Antenna design
[4], then this antenna is highly recommended for all single ended 868 / 915 / 955 MHz
designs prior to other available solutions."

referring to (DN024). Analyzing its efficiency at 915MHz in CC-Antenna DK2, however, we get the value of 43.27%.

So, my question is: why does TI recommend DN024 for 915MHz? Isn't this antenna way less efficient than DN606?

  • 0
    TI__Guru**** 317180 points

    I have assigned this to our antenna expert. 

  • 0 in reply to TER
    TI__Mastermind 33660 points

    Hi,

    Antenna #9 on CC-Antenna-DK2 is the first recommended choice for 868/915/920 MHz. This is the antenna we use on the LPs and achieve excellent efficiency. This antenna can also be used for dual-band application such as 868 MHz and 2.44 GHz. If it optimized for these frequencies, then the 915 MHz efficiency s reduced.

    For 868/915 MHz, please refer to the LAUNCHXLCC1352P-1 design. The antenna on this LP has approx 80% efficiency at 868/915 MHz; this has been optimized for 868/915 MHz whilst having a slight degradation on 2.4 GHz. The final length of the antenna is dependent on the GND plane. Hence, the reason the length of this antenna is different on CC1310 LP and CC1352 LP.

    Would not recommend to use antenna #10 no more, since this has too many vias that are serial in the antenna trace which become too dependent on the PCB thickness. 

    Regards,

        Richard

  • 0 in reply to RGW
    Intellectual 610 points

    Hi Richard, thanks for your answer,

    Antenna #9 on CC-Antenna-DK2 is exactly the one I mentioned in my question (DN024).

    It has an efficiency of 80% at 868MHz and 64% at 2.4GHz. However, according to the same document, its efficiency at 915MHz is only 43% (image below). 

    From these measurements, one could infer that Antenna #9's efficiency is good for 868MHz and 2.4GHz, but not so good at 915MHz. I can't see how 868MHz and 915MHz are mentioned as having both a good efficiency, given that the results for them are way different.

    Am I getting something wrong? If so, what would be the correct estimated efficiency for Antenna #9 at 915MHz?

    Thank you for your attention,

    Bruno

  • 0 in reply to RGW
    Intellectual 610 points

    Hi, Richard

    I may not have expressed myself clearly in the last comment.

    My application runs at 915MHz +- 5MHz. Basically, I would like to know why to choose an antenna with 43% efficiency at 915MHz (Antenna #9 from DK2, as shows the figure in the last comment) instead of an antenna with 63.4% efficiency (Antenna #10 from DK1). 

    Are there some other characteristics that make DK2 Antenna #9 potentially better than DK1 Antenna #10, despite its lower efficiency? 

    I appreciate your attention,

    Regards,

    Bruno Lau da Costa

  • 0 in reply to Bruno Lau da Costa
    TI__Mastermind 33660 points

    Hi,

    When tuning this antenna, it can be optimized with focus on:

    (A). good performance at 868/2440 MHz with degradation at 915 MHz; or

    (B). good performance at 868/915 with degradation at 2440 MHz.

    The antenna in the CC-Antenna-DK2 has been tuned according to (A). However, the same antenna used on LaunchXL-CC1310 has been tuned according to (B). The delta is in the GND plane size and length of the antenna.

    Regards,

       Richard

  • 0 in reply to RGW
    TI__Mastermind 33660 points

    Hi,

    CTIA report for LaunchXL-CC1310 at 915 MHz.

    The efficiency number is based upon 0 dBm, and not 14 dBm. Hence, the 2373 %. The TRP is 13.75 dB. i.e. 0.25 dB loss.

    5226.CC1310 LP V1_2 - 14 dBm cond_CTIA Report (RP_915.000_tot).Pdf