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  • TI Thinks Resolved

CC1310: metal plane distance from custom PCB with DN038 helical antenna design

Prodigy 50 points

Replies: 3

Views: 92

Part Number: CC1310

Dear sir,

I am creating a custom PCB with the CC1310 RF transceiver and the DN038 antenna layout. For packaging reason, the antenna layout will be close to a metal plane, so I am looking for some suggestions about the minimal distance required between the antenna and such undesired ground plane in the vertical direction (beneath the antenna) for acceptable performance. Obviously, I imagine that I have to optimize the antenna network matching due to this ground plane, but probably the efficiency will be limited if such distance is limited to few mm. Do you have any minimal distance? Is there also a minimal distance required between the antenna and a plastic wall? Can the DN024 layout, instead, be used with a bottom ground plane to overcome this problem? Many thanks.

 

Best regards

  • Genius 16070 points

    Hi,

    I presume the metal plane will also be grounded. The closer the GND plane/metal to the antenna, will reduce the BW and the efficiency of the antenna since it will be loading the antenna. DN038 is a nice little antenna for 868 MHz or 915 MHz but the bandwidth (BW) is quite small. Most final products would like to cover both 868 MHz (Europe) and 915 MHz (US) ISM bands. If you are just looking at a single band then this reduces the requirement slightly.

    A "general rule of thumb" is to try to maintain at least 5% of the wavelength distance to the antenna in order not to severely reduce/affect the performance.   

    Both DN038 and DN024 are monopole antennas which are dependent on the GND plane size so the effects will be similar. However, DN024 is a larger antenna with a larger BW and greater efficiency. Also, the exact length of the antenna is dependent on the GND plane size.

    The tricky part with antennas is the mechanical constraints of the final product will always affect the performance. If you try to maximize the volume that you have available for the antenna whilst maintaining a clearance distance in order not to load the antenna to the surroundings will give the best performance.

    If you can share your layout and  mechanical constraints then I can review it more.

    Regards,

       Richard

     

  • In reply to RGW:

    Dear Richards,

    Many thanks for replying me. I am just finalizing my layout so, I would like to figure out some more aspects before completing it.  I am just interested to the 868 MHz and  the performance in term of bandwidth for my application can be poor.  Looking at the swra416 and swra524a documents,  the suggested layout antenna seems tune for the 0.8 mm PCB thickness. How should I change it if i want to consider a 1.6 mm PCB thickness and  I want to optimize the antenna for just 868 Mhz comunication ( sorry, I am not an expert in RF communication and probably I am asking something really banal)? Obviously, by changing the PCB thickness,  I should  also change the pi matching impedance network to maximize power and this is clear to me. Many thanks 

    Best regards

    Luca 

  • Genius 16070 points

    In reply to Luca Belsito:

    Hi Luca,

    CC-Antenna-DK2 is 1.6 mm thick PCB so I would copy the antenna designs on this board. 

    DN024 is CC-Antenna-DK2#9

    DN038 is CC-Antenna-DK2#6

    DN038 antenna is sensitive to the PCB thickness since the total length of the antenna is dependent on the via length (PCB thickness). DN024 is not so sensitive for PCB thickness.

    Regards,

       Richard

     

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